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Fig. 7 | BMC Plant Biology

Fig. 7

From: Combined transcriptome and metabolome analysis reveals the effects of light quality on maize hybrids

Fig. 7

Specific genes and metabolites involved in maize heterosis establishment under various light conditions. A Proposed pathway describes the action of glutathione transferases (GSTs) in darkness. The pathway indicates that glutathione (GSH) is synthesized in two steps: first, γ-glutamyl-cysteine (γ-Glu-Cys) is formed from glutamate (Glu) and cysteine (Cys), followed by the addition of glycine (Gly) by glutathione synthetase. GSH is generally found in the nucleus (Nuc) and cytoplasm (Cyt), and the GSH/GSSG (glutathione disulfide) ratio in the nucleus influences gene expression, the cell cycle, and defense responses. Furthermore, GST can catalyze GSH to regenerate Glu. B The pathway of photosynthesis under red light condition proposed by Li et al. [51] with minor modifications. First, CO2 enters the mesophyll cytoplasm (Cyt) and is converted to bicarbonate (HCO3−). HCO3− and phosphoenolpyruvate (PEP) produce oxaloacetate (OAA) under the action of phosphoenolpyruvate carboxylase (PEPC). OAA is converted to malate by malate dehydrogenase (MDH) in the mesophyll chloroplast (Chl), and this malate diffuses into the chloroplasts of bundle sheath cells. Malate is decarboxylated by malic enzyme (ME) to produce pyruvate and CO2. Finally, CO2 enters the Calvin cycle and is fixed, thus producing sugar. In addition, pyruvate is recruited to mesophyll cells and converted to PEP by pyruvate orthophosphate dikinase (PPDK). C Proposed biosynthesis of terpenoids via the 2-C-methylerythritol 4-phosphate (MEP) pathway under blue light conditions. The pathway is simplified from Nagegowda et al. [52]. Terpenoids are synthesized from isopentenyl diphosphate (IDP) and its allylic isomer dimethylallyl diphosphate (DMADP), the products of the MEP pathway in plastids. The MEP pathway starts with pyruvate and glyceraldehyde-3-phosphate (GAP), which undergo a series of enzymatic reactions conducted by 1-deoxy-D-xylulose-5-phosphate synthase (DXS), 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), and 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase (MCT) to produce isopentenyl diphosphate (IDP) and dimethylallyl diphosphate (DMADP). The resulting terpenoids are then modified by cytochrome P450 monooxygenase (CYP450). (D) Mid-parent heterosis (MPH) of candidate genes under various light conditions. (E) MPH of candidate metabolites under various light conditions. Abbreviations: CMK, 4-(cytidine 5′-diphospho)-2-C-methyl-D-erythritol kinase; MDS, 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase; HDS/HDR, 4-hydroxy-3-methylbut-2-enyl diphosphate synthase/reductase; IDI2, isopentenyl diphosphate isomerase; GDP, geranyl diphosphate; FDPS, farnesyl diphosphate synthase; GGDPS, geranylgeranyl diphosphate synthase; Mon, monoterpenes (C10); Ses, sesquiterpenes (C15); Tri, triterpenes (C30); Dit, diterpenes (C20); Tet, tetraterpenes (C40); CYP450, cytochrome P450 monooxygenase. DMPH, FMPH, RMPH, and BMPH represent MPH of plants grown in darkness and far-red, red, and blue light conditions, respectively

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