Skip to main content
Download PDF

Exogenous melatonin enhances the growth and production of bioactive metabolites in Lemna aequinoctialis culture by modulating metabolic and lipidomic profiles

BMC Plant Biology volume 22, Article number: 545 (2022) Cite this article

Abstract

Background

Lemna species are cosmopolitan floating plants that have great application potential in the food/feed, pharmaceutical, phytoremediation, biofuel, and bioplastic industries. In this study, the effects of exogenous melatonin (0.1, 1, and 10 µM) on the growth and production of various bioactive metabolites and intact lipid species were investigated in Lemna aequinoctialis culture.

Results

Melatonin treatment significantly enhanced the growth (total dry weight) of the Lemna aequinoctialis culture. Melatonin treatment also increased cellular production of metabolites including β-alanine, ascorbic acid, aspartic acid, citric acid, chlorophyll, glutamic acid, phytosterols, serotonin, and sucrose, and intact lipid species; digalactosyldiacylglycerols, monogalactosyldiacylglycerols, phosphatidylinositols, and sulfoquinovosyldiacylglycerols. Among those metabolites, the productivity of campesterol (1.79 mg/L) and stigmasterol (10.94 mg/L) were the highest at day 28, when 10 µM melatonin was treated at day 7.

Conclusion

These results suggest that melatonin treatment could be employed for enhanced production of biomass or various bioactive metabolites and intact lipid species in large-scale L. aequinoctialis cultivation as a resource for food, feed, and pharmaceutical industries.

Background

Lemna aequinoctialis is a member of the aquatic monocotyledonous Lemnaceae family (duckweeds) and is one of the simplest and smallest plants [1, 2]. Duckweeds usually inhabit ponds, pools, and lakes across the globe, ranging from tropical to boreal regions [3, 4]. They grow rapidly (doubling time between 1.34 and 4.54 days), and have numerous potential applications in food/feed, pharmaceutical, phytoremediation, biofuel, and bioplastic industries [5,6,7,8,9,10]. Members of the Lemnaceae family including the Lemna species contain a high amount of primary metabolites, such as amino acids and starch, and a variety of secondary metabolites, such as flavonoids, hydroxycinnamic acids, and terpenoids [6, 11].

Melatonin has multiple functions in plants. As an amphiphilic molecule, melatonin is ubiquitous in all intracellular plant compartments [12], and was reported to play key roles in various plant responses and development [13]. Recently, melatonin was suggested as a plant hormone when the first phytomelatonin receptor, CAND2/PMTR1, in Arabidopsis thaliana, which governs stomatal closure in response to stress, was discovered [14]. It has also been reported that melatonin stimulates lateral and adventitious root formation in Arabidopsis thaliana through an auxin-independent mechanism [15]. Exogenous melatonin regulates the flowering and bud formation of apple trees, and similarly to animals, also acts as a signal of environmental light that regulates plant reproduction [16]. Melatonin has been proven to protect plants from reactive oxygen species (ROS) and reactive nitrogen species (RNS) by reducing free radical production [17,18,19]. In addition, it has been suggested that melatonin can directly scavenge reactive species through mechanisms, such as radical adduct formation, hydrogen atom transfer, and single electron transfer [20]. Melatonin has also been reported to enhance antioxidant activity by increasing the levels of the endogenous antioxidants ascorbic acid and glutathione [21]. Furthermore, it increases the efficiency of the electron transport chain by scavenging ROS and RNS produced in the mitochondria and reducing the loss of glutathione and protein damage [22]. Melatonin also protects plants from various abiotic and biotic stresses, such as acid rain, cold, drought, pathogens, infections, heavy metals, herbicides, salinity, and high temperature [23,24,25,26,27], and stabilizes the photosynthetic network under light and temperature stress conditions [13, 28,29,30].

The main aim of this study is to investigate the effect of melatonin on the growth, metabolic/lipidomic profile, and bioactive metabolite production of L. aequinoctialis culture and to suggest its potential application in various industries. We hypothesized that melatonin treatment would modulate the growth and production of bioactive metabolites and lipids in L. aequinoctialis cultures. Gas chromatography-mass spectrometry (GC-MS) and nano-electrospray ionization-mass spectrometry (nanoESI-MS) were employed to analyze various metabolites and intact lipid species in melatonin-treated L. aequinoctialis cultures.

Results

Effect of exogenous melatonin on the growth of L. aequinoctialis.

Figure 1 shows photographs of cultivated L. aequinoctialis, which were taken every 7 days. As shown in Fig. 2, when compared to the control group, the total number of fronds harvested at day 14 was significantly higher only in the 10 µM melatonin treatment group. At day 28, it was significantly higher in the 0.1, 1, and 10 µM melatonin treatment groups. When compared to the control group, the dry weight (g/L) significantly increased in the 1 and 10 µM melatonin treatment groups at day 14, and in the 0.1, 1, and 10 µM melatonin treatment groups at day 28. In the 1 µM melatonin treatment group, there was no difference in the dry weight per frond. In addition, in the 0.1 and 10 µM melatonin treatment groups, both the dry weight per frond and the number of fronds increased, thus increasing the total dry weight.

Fig. 1
figure 1

 L. aequinoctialis culture under various melatonin treatment concentrations at days 7, 14, 21, and 28

Full size image
Fig. 2
figure 2

Effects of various melatonin treatment concentrations on the growth of L. aequinoctialis culture. Total number of fronds at day 14 (A) and day 28 (B); total dry weight at day 14 (C) and day 28 (D); and dry weight of one frond at day 14 (E) and day 28 (F). Vertical bars and error bars indicate the mean and standard deviation (n = 3) of each treatment group. An asterisk denotes significant differences (p < 0.05) between the control and treatment groups based on the Mann-Whitney test

Full size image

Effect of melatonin treatment on the metabolic profiles in L. aequinoctialis culture.

Table S1 lists the various L. aequinoctialis metabolites detected by GC-MS analysis. A total of 49 metabolites were detected: four alcohols, 15 amino acids, four fatty acids, nine organic acids, two phenolics, three phytosterols, four sugars, and eight other assorted compounds. Figure 3 shows the relative levels (relative intensity/g) of L. aequinoctialis metabolites cultivated under 0.1, 1, and 10 µM melatonin concentrations at days 14 and 28 (Table S2 and S3, respectively). The relative levels (relative intensity/g) of α-alanine, β-alanine, aspartic acid, caffeic acid, campesterol, glycerol-3-phosphate, serine, serotonin, stigmasterol, and sucrose were significantly increased at day 14 in the melatonin treatment groups compared to the control group. The relative levels (relative intensity/g) of β-alanine, ascorbic acid, aspartic acid, campesterol, citric acid, ferulic acid, glutamic acid, β-sitosterol, stigmasterol, and sucrose were significantly increased at day 28 in the melatonin treatment groups compared to the control group. We speculate that melatonin supplementation induced the increased levels of various metabolites in L. aequinoctialis cultures.

Fig. 3
figure 3

Relative levels of L. aequinoctialis culture metabolites under various melatonin concentrations. A pathway diagram of the relative levels (relative intensity/g) of metabolites was proposed in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database (http://www.genome.jp/kegg/). Data were normalized to an internal standard (myristic-d27 acid) and then multiplied by 1,000 times for simplicity. Vertical bars and error bars indicate the mean and standard deviation (n = 9, three biological replicates and three technical replicates) of the control group and the 0.1, 1, and 10 µM melatonin treatment groups on days 14 and 28. Black bars indicate no significant differences, red bars indicate statistically significant increases, and blue bars indicate statistically significant decreases by using the Kruskal-Wallis test followed by the Mann-Whitney test as a post hoc analysis with Bonferroni’s correction (p < 0.0083)

Full size image

Effect of melatonin treatment on the lipidomic profiles in L. aequinoctialis culture

Table S4 lists the various intact lipid species found in L. aequinoctialis culture detected by nanoESI-MS analysis. A total of 51 lipids were detected: six digalactosyldiacylglycerols (DGDGs), six monogalactosyldiacylglycerols (MGDGs), three phytyl derivatives, three triacylglycerols (TGs), eleven phosphatidic acids (PAs), five phosphatidylglycerols (PGs), six phosphatidylinositols (PIs), and eleven sulfoquinovosyldiacylglycerols (SQDGs). Figure 4 shows the relative lipid levels (relative intensity/g) in L. aequinoctialis cultivated under 0.1, 1, and 10 µM melatonin concentrations and harvested on days 14 and 28 (Table S5 and S6, respectively). When compared to the control group, the relative levels (relative intensity/g) of the DGDGs (16:1/18:3, 16:0/18:3, 16:0/18:2, 18:3/18:3, and 18:2/18:2), MGDGs (16:1/18:3, 18:3/18:3, and 18:2/18:3), phytyl derivatives (chlorophyll a and b), TGs (16:0/18:2/18:3, 16:0/18:1/18:1, and 18:3/18:3/18:3), PGs (16:0/18:2, 16:0/18:1, and 16:0/18:0), PIs (16:0/18:2 and 16:0/18:1), and SQDGs (16:0/18:1, 16:0/18:0, and 18:3/18:3) were significantly increased by day 14 in the melatonin treatment groups. When compared to the control group, the relative levels (relative intensity/g) of the DGDG (16:1/18:3), MGDGs (16:1/18:3, 16:0/18:3, and 18:1/18:2), TG (16:0/18:1/18:1), PG (16:0/18:0), PIs (16:0/18:2 and 16:0/18:1), and SQDGs (16:0/18:0 and 18:3/18:3) were significantly increased by day 28 in all melatonin treatment groups. Unlike the metabolites, which accumulated over time, the intact lipid species either increased or decreased. Nevertheless, we speculate that melatonin induced the increased levels of various intact lipid species in L. aequinoctialis cultures.

Fig. 4
figure 4

Relative levels of intact lipid species of L. aequinoctialis culture cultivated under various melatonin concentrations. A pathway diagram of relative (relative intensity/g) lipid levels was proposed in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database (http://www.genome.jp/kegg/). The data were normalized to an internal standard (PE 17:0/17:0) and then multiplied 100 times for simplicity. Vertical bars and error bars indicate the mean and standard deviation (n = 9, three biological replicates and three technical replicates) of the control group and the 0.1, 1, and 10 µM melatonin treatment groups on days 14 and 28. Black bars indicate no significant differences, red bars indicate statistically significant increases, and blue bars indicate statistically significant decreases by using the Kruskal-Wallis test followed by the Mann-Whitney test as a post hoc analysis with Bonferroni’s correction (p < 0.0083)

Full size image

The metabolic and lipidomic profiles, including the quality control samples (QC samples), were plotted using PCA-derived score plots (Fig. 5). When placed in the middle of the PCA-derived score plots, the QC samples were clustered and distinctly separated from the other samples, suggesting high stability and reproducibility of GC-MS and nanoESI-MS analyses.

Fig. 5
figure 5

Principal component analysis (PCA)-derived score plots of metabolites and intact lipid species including QC samples of L. aequinoctialis. QC, quality control; control, control group (no melatonin treatment); 0.1 µM, 0.1 µM melatonin treatment; 1 µM, 1 µM melatonin treatment; 10 µM, 10 µM melatonin treatment at days 14 and 28

Full size image

Effect of various melatonin treatment time points on the productivity of L. aequinoctialis culture phytosterols

Exogenous melatonin treatment significantly increased the total dry weight and relative levels (relative intensity/g) of various L. aequinoctialis metabolites and intact lipid species and was most effective at 10 µM. To determine the productivity of L. aequinoctialis, a dosage of 10 µM melatonin, which increased the total frond dry weight the most, was selected based on our earlier results. This is because the relative yield (relative intensity/L) was obtained by multiplying the relative level (relative intensity/g) and total dry weight (g/L). Table 1 lists the relative yields (relative intensity/L) of the L. aequinoctialis culture according to various 10 µM melatonin treatment timings (days 0, 7, and 14). In the day 7 and day 14 treatment groups, the relative yields (relative intensity/L) of the comprehensive metabolites were significantly increased compared to the day 0 treatment group. The relative yields of the phytosterols were also significantly increased, reaching 142.69 relative intensity/L in the day 14 treatment group when compared to the control (81.80 relative intensity/L) and day 0 treatment groups (124.41 relative intensity/L). In this case, we speculate that melatonin acted as a growth stimulant in the early stages of the rapid growth phase of L. aequinoctialis.

Table 1 Relative yields of significantly altered metabolites of L. aequinoctialis culture cultivated under various melatonin treatment timings
Full size table

Among the various metabolites identified by metabolic profiling, phytosterols were selected as the bioactive metabolites for absolute quantification, and the optimal time under 10 µM melatonin treatment for the productivity of each of these metabolites was investigated. Table 2 lists the regression equation, correlation coefficient, limit of detection (LOD), and limit of quantification (LOQ) of the standard compounds (campesterol, β-sitosterol, and stigmasterol). The productivity (mg/L) of these compounds in L. aequinoctialis culture according to various melatonin treatment timings on days 0, 7, and 14 are listed in Table 3. The highest levels of campesterol (1.79 mg/L) and stigmasterol (10.94 mg/L) were observed in the day 7 treatment group. The highest levels of β-sitosterol (7.03 mg/L) were achieved in the day 14 treatment group.

Table 2 Regression equation, correlation coefficient (r2 values), LOD, and LOQ of phytosterol standard compounds
Full size table
Table 3 Productivity (mg/L) of phytosterols in L. aequinoctialis culture according to various melatonin (10 µM) treatment timings
Full size table

Discussion

In our study, β-alanine, citric acid, and ascorbic acid levels were increased by melatonin treatment. β-alanine and citric acid are known to contribute to the antioxidant system of plants [31, 32, 30, 31]. β-alanine is also known as an osmoprotective molecule in Gossypium herbaceum under drought conditions [33]. Citric acid also acts as an osmolyte, assisting in the maintenance of osmotic potential and balance of sodium ions and pH in cells, thereby modulating drought and alkali stress in Solanum tuberosum [34, 35]. Catalase and ascorbate peroxidase, which scavenge hydrogen peroxide, are both boosted by exogenous citric acid [32]. Ascorbic acid is a stable antioxidative molecule that scavenges ROS, such as superoxide and hydroxyl radicals, either directly or through enzyme catalysis, and is involved in photosynthesis and plant defense redox pathways [36, 37]. Ascorbic acid improved the growth of Hibiscus esculentus by protecting amino acids and protein contents from drought-induced oxidative stress [36]. It was also reported that melatonin regulated enzymes related to the redox network, increasing the activity of ascorbate peroxidase in Citrullus lanatus [37]. We speculate that various antioxidative mechanisms were activated by melatonin treatment and contributed to the enhanced growth of the L. aequinoctialis culture.

In plants, serotonin (5-hydroxytryptamine) was involved in growth and defense processes, such as regulation of the root system, shoot organogenesis, flower development, biomass production, and defense gene expression [38]. An increased endogenous serotonin level was reported in shoots and young flower buds, suggesting that serotonin is required for shoot and flower organogenesis [39, 40]. We speculate that the melatonin-induced increase in serotonin level stimulated the growth of the L. aequinoctialis culture.

Plants assimilate amino acids from inorganic nitrogen sources, and nitrogen metabolism is closely related to carbon metabolism, which is essential for plant growth [41]. Nitrogen absorbed from roots is converted to aspartic acid in the presence of oxaloacetate [42]. Glutamic acid, a product of nitrogen assimilation, is synthesized via the TCA cycle and is a synthetic precursor for the synthesis of other amino acids used for chlorophyll, protein, and nucleic acid synthesis [43]. Glutamic acid and aspartic acid are also used as biostimulants, and their co-treatment increased the biomass and height of tomatoes by improving photosynthetic biochemical reactions, pore release, and CO2 assimilation rates [44]. Increased glutamic and aspartic acids by melatonin treatment might imply that melatonin improved nitrogen metabolism and stimulated various physiological processes in the L. aequinoctialis culture for enhanced growth.

Lipid metabolism is essential for plant growth, development, and environmental stress response [45]. Glycerophospholipids are major components of plant cell membranes, serving as binding sites for intracellular or intercellular proteins, providing energy for cellular metabolism, and acting as sources for the synthesis of signaling molecules related to growth, development, and survival under adverse environmental conditions [46]. Among glycerophospholipids, PI is either a membrane-derived secondary messenger that regulates signaling pathways or its precursor [47]. Increased PI levels are associated with plant cell growth, as a 5-fold higher PI level was found in elongated cells of the maize pulvini and Arabidopsis thaliana [48, 49]. An elevation in PI metabolism is associated with increased membrane biogenesis, cytoskeletal reorganization, and Ca2+ release for cell elongation by stomatal movement regulation [50]. As seen in a previous study where melatonin stimulated PI in sweet potatoes [51], melatonin treatment in our study led to increased relative levels (relative intensity/g) of PIs (16:0/18:2 and 16:0/18:1) at days 14 and 28 in the L. aequinoctialis cultures. This implies that melatonin greatly increased the levels of the PIs, which are major components of cell membranes and stomatal movement, and could further enhance cell proliferation in the L. aequinoctialis culture.

MGDG and DGDG are the two dominant galactolipids present in the thylakoid membrane and are essential for chloroplast biosynthesis and photoautotrophic growth [52]. They are important for photosynthesis and ultimately affect the development of grains and their flowers [53, 54]. SQDG is also a major lipid component of the thylakoid membrane and directly contributes by binding to the chlorophyll-protein complex to maintain the structure and function of the photosystem II complex [55, 56]. The SQDG complexes are essential for the stability of photosystem II activity under stress conditions [57]. The increased relative levels (relative intensity/g) of MGDG, DGDG, and SQDG by melatonin treatment indicate that melatonin contributed to the enhanced growth of L. aequinoctialis by promoting photosystem II photoreaction.

Melatonin also increased the relative levels of chlorophyll a and b in the L. aequinoctialis cultures at day 14 in our study. Chlorophyll is a vital molecule in plant photosynthesis, and the energy created during this process is required for carbohydrate synthesis; hence, chlorophyll conservation is important for plant survival, development, and final production [58]. Melatonin has been shown to prevent the breakdown of chlorophyll molecules [59] and upregulate ferredoxin, which protects chlorophyll from destruction by promoting the PetF gene [60]. Melatonin also boosted the photosynthetic capability in maize by increasing the chlorophyll content and upregulating the expression of photosynthetic marker genes, such as rubisco and chlorophyll A/B-binding protein [61]. Melatonin treatment resulted in increased chlorophyll levels in the L. aequinoctialis culture at day 14, implying that melatonin, which is associated with greater chlorophyll synthesis and slower breakdown, boosted L. aequinoctialis culture growth.

Phytosterols have been reported to possess low-density lipoprotein cholesterol-lowering activity in patients with type 2 diabetes [62], and antiproliferative activity in human leukemic U937 cells [63]. As listed in Table 3, the highest productivities of campesterol (1.79 mg/L) and stigmasterol (10.94 mg/L) were observed in the day 7 treatment group. The highest productivity of β-sitosterol (7.03 mg/L) was seen in the day 14 treatment group. In the day 7 and 14 treatment groups, the productivity of total phytosterols (campesterol, β-sitosterol, and stigmasterol) increased 1.63-fold, reaching 19.5 and 19.6 mg/L, respectively, compared to the control (12.0 mg/L). In addition, the productivity of total phytosterols increased 1.15 times (19.6 mg/L) in the day 14 treatment group compared to the day 0 treatment group (17.0 mg/L). The enhanced productivity of the phytosterols in the L. aequinoctialis cultures could be due to the increased biomass and terpenoid biosynthesis by melatonin treatment. Further studies employing transcriptomic or proteomic analyses would confirm the effect of melatonin treatment on the enhanced phytosterol biosynthesis. The higher phytosterol productivity in the day 7 and day 14 treatment groups, as compared to the day 0 treatment group, may have occurred because more L. aequinoctialis fronds were initially exposed to melatonin compared to those in the day 0 treatment group.

Conclusion

In this study, we found that melatonin treatment enhanced the growth of the L. aequinoctialis culture and the production of various metabolites and intact lipid species. The importance of our study is that we obtained comprehensive metabolic and lipidomic profiles in a melatonin-treated plant system for the first time and confirmed the enhanced production of phytosterols by absolute quantification in the L. aequinoctialis culture. The increased metabolites and intact lipid species by melatonin treatment may have contributed to the increased growth of the L. aequinoctialis culture by enhancing several physiological functions, such as antioxidative mechanisms, nitrogen metabolism, and the photosynthetic system. Further research related to the melatonin signaling cascade, melatonin receptors, and interacting proteins using transcriptomics and proteomics could be performed to reveal more in-depth melatonin-mediated mechanisms in the future. In addition, melatonin treatment could be applied to the large-scale cultivation of L. aequinoctialis to produce various metabolites and intact lipid species for utilization in functional food/feed or pharmaceutical industries.

Methods

Cultivation of L. aequinoctialis

L. aequinoctialis (PC-10,605) was obtained from the Korean Collection for Type Cultures (KCTC; Biological Resource Center, Jeongeup, Republic of Korea), and was cultivated as previously reported [64]. Briefly, half-strength Murashige and Skoog’s basal medium supplemented with 1 mg/L benzylaminopurine, 30 g/L sucrose, and 6 g/L Gelrite were used for the cultivation of L. aequinoctialis, which was subcultured once every 2 weeks. The pH of the medium was adjusted to 5.8 prior to autoclaving at 121℃ for 20 min. Prior to melatonin treatment, L. aequinoctialis was cultivated in 1 L of liquid media for 3 days under the same environmental conditions. Then, 30 fronds of the plants were inoculated into 100 mL of liquid medium with the same composition in solid medium, except for Gelrite. The plants were cultivated in static liquid medium at 25℃, 81 ~ 84 µmol/m2/sec light intensity, and a 16 h light–8 h dark photoperiod in an incubator (NEX-202 M, EYELA, Nexus Technologies, Seoul, Republic of Korea).

Melatonin treatment

L. aequinoctialis fronds were inoculated into 250 mL Erlenmeyer flasks (Diamond, Republic of Korea) containing 100 mL of liquid 1/2MS1BA medium and cultured at 25 °C, 6000 lx light intensity, and 16 h light–8 h dark conditions. Melatonin (0.1, 1, and 10 µM) was added to the flasks at day 0 to investigate the effect of melatonin on growth, metabolite, and intact lipid species profiles of L. aequinoctialis culture. The sampling timings of days 14 and 28 were determined from preliminary experiments based on the total plant growth of L. aequinoctialis culture (Fig. S1).

To further investigate the optimal melatonin treatment timing for enhanced productivities of selected metabolites (serotonin, campesterol, β-sitosterol, and stigmasterol), 10 µM melatonin was added to different L. aequinoctialis cultures on days 0, 7, and 14 (for the timed 10 µM dosage treatment). All experiments were performed in three biological replicates.

Growth measurement

The total number of L. aequinoctialis fronds was counted every 7 days. To measure total dry weight, harvested whole plants were washed with distilled water and dried for 15 min. The plants were stored in a deep freezer (-70 °C) for 2 days and freeze-dried (Bondiro, Ilshin Lab. Co., Seoul, Republic of Korea) for 24 h, and the total dry weight was then measured.

Comprehensive metabolite profiling by GC-MS analysis

Freeze-dried samples were ground with a mortar and pestle, and 20 mg of each L. aequinoctialis sample was separately weighed and transferred into tubes (Axygen, Union City, CA, USA). Extraction and GC-MS analysis of L. aequinoctialis metabolites were conducted according to the previously described method [64]. Briefly, samples were extracted with 1 mL of methanol and sonicated for 30 min. After sonication, the supernatants were filtered through 0.45 μm polytetrafluoroethylene (PTFE) syringe filters (Whatman, Maidstone, UK). Two hundred microliters of each L. aequinoctialis plant sample was transferred into GC vials and dried with nitrogen gas for 5 min. After derivatization, GC-MS analysis of L. aequinoctialis metabolites was conducted according to the previously described method [63]. Briefly, for derivatization, 30 µL of 20,000 µg/mL methoxylamine hydrochloride in pyridine, 50 µL of BSTFA (N,O-bis[trimethylsilyl]trifluoroacetamide; Sigma-Aldrich, St, Louis, MO, USA) containing 1% trimethylchlorosilane, and 10 µL of 2,000 µg/mL myristic-d27 acid (Tokyo Chemical Industry Co., Japan) in pyridine (Sigma-Aldrich, St, Louis, MO, USA) as an internal standard were added to the dried samples and the mixtures were incubated in a 65℃ water bath for 60 min. One microliter of each sample was then injected into the GC-MS (7890 A, Agilent Technologies, Santa Clara, CA, USA) with a DB-5 MS column (Agilent Technologies, Santa Clara, CA, USA), and the auxiliary, MS source, and quadrupole temperatures were set to 280, 230, and 150℃, respectively. The initial oven temperature was set to 60℃ and elevated up to 310℃ at 5℃/min.

Comprehensive intact lipids species profiling by nanoESI-MS analysis

Five milligrams of each ground L. aequinoctialis sample was separately weighed, and extraction and nanoESI-MS analysis of the intact lipid species of L. aequinoctialis were performed as previously reported [65, 66]. Briefly, samples were added to 300 µL of methanol containing 0.01% butylated hydroxytoluene (BHT), 1,000 µL of methyl-tert-butyl ether (MTBE) containing 0.01% BHT, and 1,2-diheptadecanoyl-sn-glycero-3-phosphoethanolamine (PE 17:0/17:0) as an internal standard and were incubated on a shaker at room temperature for 1 h. Afterward, 250 µL of water containing 0.01% BHT was added and the samples were centrifuged, then 900 µL of the upper phase was collected. The lower phase was added to 250 µL of MTBE, 75 µL of methanol, and 62.5 µL of water, centrifuged, and then collected with the first upper phase. Next, the extracts were filtered through 0.45 μm PTFE syringe filters and 900 µL of each sample was transferred into vials and dried with nitrogen gas for 2 h. NanoESI-MS analysis of the intact lipid species of L. aequinoctialis was performed as previously reported [24]. The samples were analyzed in triplicate by a linear ion-trap mass spectrometer (LTQ-XL; ThermoFisher Scientific, San Jose, CA, USA) equipped with an automated nanospray ion source (TriVersa NanoMate System, Advion Biosciences, Ithaca, NY, USA). The extracts (10 µL) were infused with a nanoelectrospray chip (5.5-µm diameter spray nozzles, Advion Biosciences, Ithaca, NY, USA) and analyzed in negative and positive ion modes. The m/z range was set at 400–1200 for a 2 min run time. The full scan mode spectra method was used for analysis and tandem mass spectrometry (MS/MS) was used to identify the lipid species.

Absolute quantification of serotonin and phytosterols

Absolute quantification of phytosterols was accomplished using the calibration curves of each standard compound. Standard curves were generated with 0.78125, 1.5625, 3.125, 6.25, 12.5, and 25 mg/L of campesterol; 0.78125, 1.5625, 3.125, 6.25, 12.5, 25, and 50 mg/L of β-sitosterol; and 3.125, 6.25, 12.5, 25, 50, and 100 mg/L of stigmasterol. GC-MS analysis for absolute quantification was performed according to the previously described method [64]. Briefly, 200 µL of each plant sample was transferred into GC vials and dried with nitrogen gas for 5 min. For derivatization, 30 µL of 20,000 µg/mL methoxylamine hydrochloride in pyridine, 50 µL of BSTFA (N,O-bis[trimethylsilyl]trifluoroacetamide; Sigma-Aldrich, St. Louis, MO, USA) containing 1% trimethylchlorosilane, and 10 µL of 2,000 µg/mL myristic-d27 acid (Tokyo Chemical Industry Co., Japan) in pyridine (Sigma-Aldrich, St. Louis, MO, USA) as an internal standard were added to the dried samples and then incubated in a 65℃ water bath for 60 min. One microliter of each sample was injected into the GC-MS (7890 A, Agilent Technologies, Santa Clara, CA, USA) with a DB-5 MS column (Agilent Technologies, Santa Clara, CA, USA), and the auxiliary, MS source, and quadrupole temperatures were set to 280, 230, and 150℃, respectively. The initial oven temperature was set to 60℃ and elevated up to 310℃ at 5℃/min. The standard calibration curves, LOD, and LOQ were also determined according to the previously reported method [64].

Data processing and statistical analysis

SPSS Statistics 26 software (IBM, Somers, Armonk, NY., USA) was used for the Kruskal-Wallis test, Mann-Whitney test, and Bonferroni’s correction. Principal component analysis (PCA) was performed using SIMCA software (version 15.0; Umetrics, Umeå, Sweden), and mean-centered and Pareto scaling were adapted for preprocessing.

Availability of data and materials

All data generated or analyzed during this study are included in this published article (and its supplementary information files).

Abbreviations

ROS:

Reactive oxygen species

RNS:

Reactive nitrogen species

GC-MS:

Gas chromatography-mass spectrometry

nanoESI-MS:

nano-Electrospray ionization-mass spectrometry

LOD:

Limit of detection

LOQ:

Limit of quantification

PCA:

Principal component analysis

DGDG:

Digalactosyldiacylglycerol

MGDG:

Monogalactosyldiacylglycerol

TG:

Triacylglycerol

PA:

Phosphatidic acid

PG:

Phosphatidylglycerol

PI:

Phosphatidylinositol

SQDG:

Sulfoquinovosyldiacylglycerol

QC:

Quality control

TCA:

Tricarboxylic acid

References

  1. Sree KS, Bog M, Appenroth KJ. Taxonomy of duckweeds (Lemnaceae), potential new crop plants. Emirates J Food Agric. 2016;28:291–302.

    Article  Google Scholar 

  2. Hillman WS. The Lemnaceae, or duckweeds: a review of the descriptive and experimental literature. Bot Rev. 1961;27:221–87.

    Article  CAS  Google Scholar 

  3. Bergmann BA, Cheng J, Classen J, Stomp AM. In vitro selection of duckweed geographical isolates for potential use in swine lagoon effluent renovation. Bioresour Technol. 2000;73:13–20.

    Article  CAS  Google Scholar 

  4. Peeters ETHM, van Zuidam JP, van Zuidam BG, Van Nes EH, Kosten S, Heuts PGM, et al. Changing weather conditions and floating plants in temperate drainage ditches. J Appl Ecol. 2013;50:585–93.

    Article  Google Scholar 

  5. Parabel L. 2021. https://www.parabel.com/lentein/. Accessed 23 Aug 2021.

  6. Appenroth KJ, Sree KS, Böhm V, Hammann S, Vetter W, Leiterer M, et al. Nutritional value of duckweeds (Lemnaceae) as human food. Food Chem. 2017;217:266–73.

    Article  CAS  PubMed  Google Scholar 

  7. Shen N, Wang Q, Zhu J, Qin Y, Liao S, Li Y, et al. Succinic acid production from duckweed (Landoltia punctata) hydrolysate by batch fermentation of Actinobacillus succinogenes GXAS137. Bioresour Technol. 2016;211:307–12.

    Article  CAS  PubMed  Google Scholar 

  8. Marín CMD-C, Oron G. Boron removal by the duckweed Lemna gibba: a potential method for the remediation of boron-polluted waters. Water Res. 2007;41:4579–84.

    Article  Google Scholar 

  9. Ya VB. Aquatic plants of the far east of Russia: a review on their use in medicine, pharmacological activity. Bangladesh J Med Sci. 2015;14:9–13.

    Article  Google Scholar 

  10. Ziegler P, Adelmann K, Zimmer S, Schmidt C, Appenroth KJ. Relative in vitro growth rates of duckweeds (Lemnaceae) - the most rapidly growing higher plants. Plant Biol. 2015;17:33–41.

    Article  PubMed  Google Scholar 

  11. Baek G, Saeed M, Choi H-K. Duckweeds: their utilization, metabolites and cultivation. Appl Biol Chem. 2021;64:73.

    Article  PubMed Central  PubMed  Google Scholar 

  12. Back K. Melatonin metabolism, signaling and possible roles in plants. Plant J. 2021;105:376–91.

    Article  CAS  PubMed  Google Scholar 

  13. Murch SJ, Erland LAE. A systematic review of melatonin in plants: an example of evolution of literature. Front Plant Sci. 2021;12:683047.

    Article  PubMed Central  PubMed  Google Scholar 

  14. Wei J, Li DX, Zhang J-R, Shan C, Rengel Z, Song Z-B, et al. Phytomelatonin receptor PMTR1-mediated signaling regulates stomatal closure in Arabidopsis thaliana. J Pineal Res. 2018;65:e12500.

    Article  PubMed  Google Scholar 

  15. Pelagio-Flores R, Muñoz-Parra E, Ortiz-Castro R, López-Bucio J. Melatonin regulates Arabidopsis root system architecture likely acting independently of auxin signaling. J Pineal Res. 2012;53:279–88.

    Article  CAS  PubMed  Google Scholar 

  16. Zhang H, Wang L, Shi K, Shan D, Zhu Y, Wang C, et al. Apple tree flowering is mediated by low level of melatonin under the regulation of seasonal light signal. J Pineal Res. 2019;66:e12551.

    Article  PubMed  Google Scholar 

  17. Reiter RJ, Tan DX, Burkhardt S, Manchester LC. Melatonin in plants. Nutr Rev. 2001;59:286–90.

    Article  CAS  PubMed  Google Scholar 

  18. Khan A, Numan M, Khan AL, Lee IJ, Imran M, Asaf S, Al-Harrasi A. Melatonin: awakening the defense mechanisms during plant oxidative stress. Plants (Basel). 2020;9:407.

    Article  CAS  PubMed  Google Scholar 

  19. Farouk S, AL-Huqail AA. Sustainable biochar and/or melatonin improve salinity tolerance in borage plants by modulating osmotic adjustment, antioxidants, and ion homeostasis. Plants (Basel). 2022;11:765.

    Article  CAS  PubMed  Google Scholar 

  20. Galano A, Tan DX, Reiter RJ. Melatonin as a natural ally against oxidative stress: a physicochemical examination. J Pineal Res. 2011;51:1–16.

    Article  CAS  PubMed  Google Scholar 

  21. Liu N, Jin Z, Wang S, Gong B, Wen D, Wang X, et al. Sodic alkaline stress mitigation with exogenous melatonin involves reactive oxygen metabolism and ion homeostasis in tomato. Sci Hortic (Amsterdam). 2015;181:18–25.

    Article  CAS  Google Scholar 

  22. León J, Acuña-Castroviejo D, Escames G, Tan D-X, Reiter RJ. Melatonin mitigates mitochondrial malfunction. J Pineal Res. 2005;38:1–9.

    Article  PubMed  Google Scholar 

  23. Arnao MB, Hernández-Ruiz J. Melatonin as a regulatory hub of plant hormone levels and action in stress situations. Plant Biol. 2021;23:7–19.

    Article  CAS  PubMed  Google Scholar 

  24. Farouk S, Al-Amri SM. Exogenous melatonin-mediated modulation of arsenic tolerance with improved accretion of secondary metabolite production, activating antioxidant capacity and improved chloroplast ultrastructure in rosemary herb. Ecotoxicol Environ Saf. 2019;180:333–47.

    Article  CAS  PubMed  Google Scholar 

  25. Fan J, Xie Y, Zhang Z, Chen L. Melatonin: a multifunctional factor in plants. Int J Mol Sci. 2018;19:1528.

    Article  PubMed Central  PubMed  Google Scholar 

  26. Altaf MA, Shahid R, Ren MX, Altaf MM, Khan LU, Shahid S, et al. Melatonin alleviates salt damage in tomato seedling: a root architecture system, photosynthetic capacity, ion homeostasis, and antioxidant enzymes analysis. Sci Hortic. 2021;285:110145.

    Article  CAS  Google Scholar 

  27. Hassan MU, Mahmood A, Awan MI, Maqbool R, Aamer M, Alhaithloul HAS, et al. Melatonin-induced protection against plant abiotic stress: mechanisms and prospects. Front Plant Sci. 2022;13:902694.

    Article  PubMed Central  PubMed  Google Scholar 

  28. Jahan MS, Shu S, Wang Y. Chen Z, He M, Tao M, et al. Melatonin alleviates heat-induced damage of tomato seedlings by balancing redox homeostasis and modulating polyamine and nitric oxide biosynthesis. BMC Plant Biol. 2019;19:414.

    Article  PubMed Central  PubMed  Google Scholar 

  29. Jahan MS, Guo S, Sun J, Shu S, Wang Y, El-Yazied AA, et al. Melatonin-mediated photosynthetic performance of tomato seedlings under high-temperature stress. Plant Physiol Biochem. 2021;167:309–20.

    Article  CAS  PubMed  Google Scholar 

  30. Jahan MS, Shu S, Wang Y, Hasan MM, El-Yazied AA, Alabdallah NM, et al. Melatonin pretreatment confers heat tolerance and repression of heat-induced senescence in tomato through the modulation of ABA- and GA-mediated pathways. Front Plant Sci. 2021;12:650955.

    Article  PubMed Central  PubMed  Google Scholar 

  31. Parthasarathy A, Savka MA, Hudson AO. The synthesis and role of β-alanine in plants. Front Plant Sci. 2019;10:921.

    Article  PubMed Central  PubMed  Google Scholar 

  32. Sun Y-L, Hong S-K. Effects of citric acid as an important component of the responses to saline and alkaline stress in the halophyte Leymus chinensis (trin.). Plant Growth Regul. 2011;64:129–39.

    Article  CAS  Google Scholar 

  33. Ranjan A, Pandey N, Lakhwani D, Dubey NK, Pathre UV, Sawant SV. Comparative transcriptomic analysis of roots of contrasting Gossypium herbaceum genotypes revealing adaptation to drought. BMC Genomics. 2012;13:680.

    Article  CAS  PubMed Central  PubMed  Google Scholar 

  34. Bethke PC, Sabba R, Bussan AJ. Tuber water and pressure potentials decrease and sucrose contents increase in response to moderate drought and heat stress. Am J Potato Res. 2009;86:519–32.

    Article  Google Scholar 

  35. Shi D-C, Yin S-J, Yang G-H, Zhao K-F. Citric acid accumulation in an alkali-tolerant plant Puccinellia tenuiflora under alkaline stress. Acta Bot Sin. 2002;44:537–40.

    CAS  Google Scholar 

  36. Baghizadeh A, Ghorbanli M, Haj RM, Mozafarih H. Evaluation of interaction effect of drought stress with ascorbate and salicylic acid on some of physiological and biochemical parameters in Okra (Hibiscus esculentus L.). Res J Biol Sci. 2009;4:380–7.

    Google Scholar 

  37. Nawaz MA, Jiao Y, Chen C, Shireen F, Zheng Z, Imtiaz M, et al. Melatonin pretreatment improves vanadium stress tolerance of watermelon seedlings by reducing vanadium concentration in the leaves and regulating melatonin biosynthesis and antioxidant-related gene expression. J Plant Physiol. 2018;220:115–27.

    Article  CAS  PubMed  Google Scholar 

  38. Erland LAE, Turi CE, Saxena PK. Serotonin: an ancient molecule and an important regulator of plant processes. Biotechnol Adv. 2016;34:1347–61.

    Article  CAS  PubMed  Google Scholar 

  39. Murch SJ, Campbell SSB, Saxena PK. The role of serotonin and melatonin in plant morphogenesis: regulation of auxin-induced root organogenesis in in vitro-cultured explants of St. John’s wort (Hypericum perforatum L.). In Vitr Cell Dev Biol - Plant. 2001;37:786–93.

    Article  CAS  Google Scholar 

  40. Murch SJ, Alan AR, Cao J, Saxena PK. Melatonin and serotonin in flowers and fruits of Datura metel L. J Pineal Res. 2009;47:277–83.

    Article  CAS  PubMed  Google Scholar 

  41. Kusano M, Fukushima A, Redestig H, Saito K. Metabolomic approaches toward understanding nitrogen metabolism in plants. J Exp Bot. 2011;62:1439–53.

    Article  CAS  PubMed  Google Scholar 

  42. Springsteen G, Yerabolu JR, Nelson J, Rhea CJ, Krishnamurthy R. Linked cycles of oxidative decarboxylation of glyoxylate as protometabolic analogs of the citric acid cycle. Nat Commun. 2018;9:91.

    Article  PubMed Central  PubMed  Google Scholar 

  43. Xie T, Gu W, Wang M, Zhang L, Li C, Li W, et al. Exogenous 2-(3,4-dichlorophenoxy) triethylamine ameliorates the soil drought effect on nitrogen metabolism in maize during the pre-female inflorescence emergence stage. BMC Plant Biol. 2019;19:107.

    Article  PubMed Central  PubMed  Google Scholar 

  44. Alfosea-Simón M, Simón-Grao S, Zavala-Gonzalez EA, Cámara-Zapata JM, Simón I, Martínez-Nicolás JJ, et al. Physiological, nutritional and metabolomic responses of tomato plants after the foliar application of amino acids aspartic acid, glutamic acid and alanine. Front Plant Sci. 2021;11:581234.

    Article  PubMed Central  PubMed  Google Scholar 

  45. Natera SHA, Hill CB, Rupasinghe TWT, Roessner U. Salt-stress induced alterations in the root lipidome of two barley genotypes with contrasting responses to salinity. Funct Plant Biol. 2016;43:207–19.

    Article  CAS  PubMed  Google Scholar 

  46. Sosa Alderete LG, Flor S, Lucangioli S, Agostini E. Impact of phenol on the glycerophospholipid turnover and potential role of circadian clock in the plant response against this pollutant in tobacco hairy roots. Plant Physiol Biochem. 2020;151:411–20.

    Article  CAS  PubMed  Google Scholar 

  47. Downes CP, Gray A, Lucocq JM. Probing phosphoinositide functions in signaling and membrane trafficking. Trends Cell Biol. 2005;15:259–68.

    Article  CAS  PubMed  Google Scholar 

  48. Perera IY, Heilmann I, Boss WF. Transient and sustained increases in inositol 1,4,5-trisphosphate precede the differential growth response in gravistimulated maize pulvini. Proc Natl Acad Sci USA. 1999;96:5838–43.

    Article  CAS  PubMed Central  PubMed  Google Scholar 

  49. Kost B, Lemichez E, Spielhofer P, Hong Y, Tolias K, Carpenter C, et al. Rac homologues and compartmentalized phosphatidylinositol 4, 5-bisphosphate act in a common pathway to regulate polar pollen tube growth. J Cell Biol. 1999;145:317–30.

    Article  CAS  PubMed Central  PubMed  Google Scholar 

  50. Stevenson JM, Perera IY, Heilmann I, Persson S, Boss WF. Inositol signaling and plant growth. Trends Plant Sci. 2000;5:252–8.

    Article  CAS  PubMed  Google Scholar 

  51. Yu Y, Wang A, Li X, Kou M, Wang W, Chen X, et al. Melatonin-stimulated triacylglycerol breakdown and energy turnover under salinity stress contributes to the maintenance of plasma membrane H+ –ATPase activity and K+/Na + homeostasis in sweet potato. Front Plant Sci. 2018;9:256.

    Article  CAS  PubMed Central  PubMed  Google Scholar 

  52. Dörmann P, Benning C. Galactolipids rule in seed plants. Trends Plant Sci. 2002;7:112–8.

    Article  PubMed  Google Scholar 

  53. Basnet R, Zhang J, Hussain N, Shu Q. Characterization and mutational analysis of a monogalactosyldiacylglycerol synthase gene OsMGD2 in rice. Front Plant Sci. 2019;10:992.

    Article  PubMed Central  PubMed  Google Scholar 

  54. Nußberger S, Dörr K, Wang DN, Kühlbrandt W. Lipid-protein interactions in crystals of plant light-harvesting complex. J Mol Biol. 1993;234:347–56.

    Article  PubMed  Google Scholar 

  55. Mizusawa N, Wada H. The role of lipids in photosystem II. Biochim Biophys Acta - Bioenerg. 2012;1817:194–208.

    Article  CAS  Google Scholar 

  56. Sato N. Roles of the acidic lipids sulfoquinovosyl diacylglycerol and phosphatidylglycerol in photosynthesis: their specificity and evolution. J Plant Res. 2004;117:495–505.

    Article  CAS  PubMed  Google Scholar 

  57. Sato N, Aoki M, Maru Y, Sonoike K, Minoda A, Tsuzuki M. Involvement of sulfoquinovosyl diacylglycerol in the structural integrity and heat-tolerance of photosystem II. Planta. 2003;217:245–51.

    Article  CAS  PubMed  Google Scholar 

  58. Tan D-X, Hardeland R, Manchester LC, Korkmaz A, Ma S, Rosales-Corral S, et al. Functional roles of melatonin in plants, and perspectives in nutritional and agricultural science. J Exp Bot. 2012;63:577–97.

    Article  CAS  PubMed  Google Scholar 

  59. Liang D, Ni Z, Xia H, Xie Y, Lv X, Wang J, et al. Exogenous melatonin promotes biomass accumulation and photosynthesis of kiwifruit seedlings under drought stress. Sci Hortic (Amsterdam). 2019;246:34–43.

    Article  CAS  Google Scholar 

  60. Wei W, Li Q-T, Chu Y-N, Reiter RJ, Yu X-M, Zhu D-H, et al. Melatonin enhances plant growth and abiotic stress tolerance in soybean plants. J Exp Bot. 2015;66:695–707.

    Article  CAS  PubMed  Google Scholar 

  61. Zhao H, Su T, Huo L, Wei H, Jiang Y, Xu L, et al. Unveiling the mechanism of melatonin impacts on maize seedling growth: sugar metabolism as a case. J Pineal Res. 2015;59:255–66.

    Article  CAS  PubMed  Google Scholar 

  62. Baker WL, Baker EL, Coleman CI. The effect of plant sterols or stanols on lipid parameters in patients with type 2 diabetes: a meta-analysis. Diabetes Res Clin Pract. 2009;84:e33–7.

    Article  CAS  PubMed  Google Scholar 

  63. Park C, Moon DO, Rhu CH, Choi BT, Lee WH, Kim G-Y, et al. β-Sitosterol induces anti-proliferation and apoptosis in human leukemic U937 cells through activation of caspase-3 and induction of Bax/Bcl-2 ratio. Biol Pharm Bull. 2007;30:1317–23.

    Article  CAS  PubMed  Google Scholar 

  64. Kim JY, Kim HY, Jeon JY, Kim DM, Zhou Y, Lee JS, et al. Effects of coronatine elicitation on growth and metabolic profiles of Lemna paucicostata culture. PLoS ONE. 2017;12:e0187622.

    Article  PubMed Central  PubMed  Google Scholar 

  65. Matyash V, Liebisch G, Kurzchalia TV, Shevchenko A, Schwudke D. Lipid extraction by methyl-tert-butyl ether for high-throughput lipidomics. J Lipid Res. 2008;49:1137–46.

    Article  CAS  PubMed Central  PubMed  Google Scholar 

  66. Kim SH, Lim SR, Hong SJ, Cho BK, Lee H, Lee CG, et al. Effect of ethephon as an ethylene-releasing compound on the metabolic profile of Chlorella vulgaris. J Agric Food Chem. 2016;64:4807–16.

    Article  CAS  PubMed  Google Scholar 

Download references

Acknowledgements

Not Applicable.

Funding

This work was supported by the National Research Foundation of Korea (NRF) grant (NRF-2022R1A5A6000760) funded by the Korean government (MSIP) and the Chung-Ang University Graduate Research Scholarship in 2021. The funding bodies played no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.

Author information

Authors and Affiliations

  1. College of Pharmacy, Chung-Ang University, 06974, Seoul, Republic of Korea

    GahYoung Baek, Hwanhui Lee, JuHee Ko & Hyung-Kyoon Choi

Authors
  1. GahYoung Baek
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Hwanhui Lee
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. JuHee Ko
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Hyung-Kyoon Choi
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

G.Y.B, H.L, and J.H.K conducted formal analysis and investigation. G.Y.B, and H.K.C wrote original draft. H.K.C wrote review and editing, supervision, funding acquisition, and project administration and produced methodology. The author(s) read and approved the final manuscript

Corresponding author

Correspondence to Hyung-Kyoon Choi.

Ethics declarations

Ethics approval and consent to participate

Not Applicable.

Consent for publication

Not Applicable.

Competing interests

There are no conflicts of interest to declare.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Additional file 1:

 Figure S1. Growth of L. aequinoctialis culture cultivated for 35 days. Total number offronds (A) and dry weight (B).Dataare mean values, and the vertical bars represent the standard deviation fromthree biological replications. TableS1.Identification of various L.aequinoctialis culture metabolites by gas chromatography-mass spectrometry(GC-MS) analysis.The base peak ineach compound among ion fragments is shown in bold characters. RT, retentiontime; TMS, trimethylsilylation; MEOX, methoxylamine hydrochloride. TableS2 Relativelevels (relative intensity/g) of various L.aequinoctialis culture metabolites cultivated under various melatoninconcentrations at day 14.Data aremean ± standard deviationvalues of nine measurements from three biological replicates and threetechnical replicates of the control group and the 0.1, 1, and 10 μM melatonin treatment groups on day 14. The valueswithin a column with different letters (a, b, and c) mean statisticallysignificant differences evaluated by using the Kruskal-Wallis test followed by theMann-Whitney test as a post hoc analysis with Bonferroni's correction (p < 0.0083). TableS3.Relative levels (relative intensity/g) of various L. aequinoctialis culture metabolites cultivated under variousmelatonin concentrations at day 28.Dataare mean ± standard deviation values of nine measurements from three biologicalreplicates and three technical replicates of the control group and the 0.1, 1,and 10 μM melatonin treatment groups on day 28. The values within a column withdifferent letters (a, b, and c) mean statistically significant differencesevaluated by using the Kruskal-Wallis test followed by the Mann-Whitney test asa post hoc analysis with Bonferroni's correction (p < 0.0083). TableS4.Identification of various intact lipid species in L. aequinoctialis culture by nano-electrospray ionization-mass spectrometry(nanoESI-MS) analysis. TableS5 Relativelevels (relative intensity/g) of various intact lipid species of L. aequinoctialis culture cultivatedunder various melatonin concentrations at day 14. Data are mean ± standarddeviation values of nine measurements from three biological replicates and threetechnical replicates of the control group and the 0.1, 1, and 10 μM melatonintreatment groups on day 14. The values within a column with different letters(a, b, and c) mean statistically significant differences evaluated by using theKruskal-Wallis test followed by the Mann-Whitney test as a post hoc analysiswith Bonferroni's correction (p < 0.0083). TableS6.Relative levels (relative intensity/g) of various intact lipid species of L. aequinoctialis culturecultivated under various melatoninconcentrations at day 28.Data aremean ± standard deviationvalues of 9 measurements from 3 biological replicates and 3 technicalreplicates of control group and 0.1 μM, 1 μM, and 10 μMmelatonin treatment groups on day 28. The values within a column withthe different letters (a, b, and c) mean statistically significant differencesevaluated byusing the Kruskal-Wallis test followed by Mann-Whitney test as post hocanalysis with Bonferroni's correction (p <0.0083). 

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Baek, G., Lee, H., Ko, J. et al. Exogenous melatonin enhances the growth and production of bioactive metabolites in Lemna aequinoctialis culture by modulating metabolic and lipidomic profiles. BMC Plant Biol 22, 545 (2022). https://doi.org/10.1186/s12870-022-03941-x

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/s12870-022-03941-x

Keywords

  • Lemna aequinoctialis
  • Melatonin
  • Metabolites
  • Lipids
  • GC-MS
  • nanoESI-MS

BMC Plant Biology

ISSN: 1471-2229

Contact us