Global analysis of cis-natural antisense transcripts and their heat-responsive nat-siRNAs in Brassica rapa
- Xiang Yu†1,
- Jun Yang†1,
- Xiaorong Li1,
- Xuxin Liu1,
- Chuanbao Sun1,
- Feijie Wu1 and
- Yuke He1Email author
© Yu et al.; licensee BioMed Central Ltd. 2013
Received: 23 August 2013
Accepted: 5 December 2013
Published: 10 December 2013
Brassica rapa includes several important leaf vegetable crops whose production is often damaged by high temperature. Cis-natural antisense transcripts (cis-NATs) and cis-NATs-derived small interfering RNAs (nat-siRNAs) play important roles in plant development and stress responses. However, genome-wide cis-NATs in B. rapa are not known. The NATs and nat-siRNAs that respond to heat stress have never been well studied in B. rapa. Here, we took advantage of RNA-seq and small RNA (sRNA) deep sequencing technology to identify cis-NATs and heat responsive nat-siRNAs in B. rapa.
Analyses of four RNA sequencing datasets revealed 1031 cis-NATs B. rapa ssp. chinensis cv Wut and B. rapa ssp. pekinensis cv. Bre. Based on sequence homology between Arabidopsis thaliana and B. rapa, 303 conserved cis-NATs in B. rapa were found to correspond to 280 cis-NATs in Arabidopsis; the remaining 728 novel cis-NATs were identified as Brassica-specific ones. Using six sRNA libraries, 4846 nat-siRNAs derived from 150 cis-NATs were detected. Differential expression analysis revealed that nat-siRNAs derived from 12 cis-NATs were responsive to heat stress, and most of them showed strand bias. Real-time PCR indicated that most of the transcripts generating heat-responsive nat-siRNAs were upregulated under heat stress, while the transcripts from the opposite strands of the same loci were downregulated.
Our results provide the first subsets of genome-wide cis-NATs and heat-responsive nat-siRNAs in B. rapa; these sRNAs are potentially useful for the genetic improvement of heat tolerance in B. rapa and other crops.
Keywordscis-NATs nat-siRNAs Heat response Genomic comparison Brassica rapa
Natural antisense transcripts (NATs) are endogenous RNA molecules that exhibit partial or complete complementarity to other transcripts. Cis-NATs are transcribed from the opposite DNA strand as their sense transcripts from the same genomic loci. Genome-wide analyses have revealed that cis-NATs are widespread in eukaryotes [1, 2]. In animal and plant genomes, l7-30% of the genes encode complementary cis-NATs [3–7]. In animals, NATs are involved in alternative splicing, DNA methylation, RNA editing and genomic imprinting [8–11]. In plants, several cis-NATs take part in gene regulatory events through cis-NAT-derived small interferering RNAs (nat-siRNAs) [12, 13]. Cis-NATs have been identified on genome-wide scale in Arabidopsis and rice [6, 14, 15]. These cis-NATs produce nat-siRNAs in the regions overlapping with sense transcripts and the nat-siRNAs exhibit strand-specificity (strand bias) .
Small non-coding RNAs are well known as an important regulatory factor in gene networks, and are widely involved in different development stages and stress responses. Based on the genomic origins of their precursors, sRNAs can be divided into four categories: microRNAs (miRNAs), trans-acting small interfering RNAs (ta-siRNAs), NAT siRNAs (nat-siRNAs), and repeat-associated siRNAs . Among these four categories, the biogenesis and function of miRNA are best understood [18, 19], and they participate in a broad range of developmental and stress response events [20, 21]. Most miRNAs are derived from intergenic regions, although some of them are processed from introns of protein-coding genes . Nat-siRNAs that participate in stress responses at specific development stage have been discovered in recent years. The first identified salt-induced nat-siRNAs were derived from the antisense overlapping gene pair of Delta (1)-pyrroline-5-carboxylate dehydrogenase (P5CDH), a stress-related gene (SRO5); 24-nt (nucleotides) siRNAs are formed by a biogenesis pathway dependent on Dicer-like 2 (DCL2), while a phase for the subsequent generation of 21-nt siRNAs are established by DCL1 . In 2006, a pathogen-induced nat-siRNA was found and its biogenesis required DCL1 . A plant sperm-specific nat-siRNA plays an important role in controlling sperm function during double fertilization . However, the general biogenesis process and regulatory mechanisms of NATs and nat-siRNAs are still largely unclear.
Brassica rapa comprises several important leaf vegetable crops, and its genome is considered to be mesohexaploid and derived from a triplicated diploid ancestral genome that was closely related to the A. thaliana genome [24, 25]. Recently, many conserved and novel miRNAs have been identified in B. rapa through sRNA deep sequencing [26, 27]. However, the genome-wide cis-NATs and heat-responsive nat-siRNAs in B. rapa are still unknown. Leaf vegetable crops are much more sensitive to high temperature than fruit vegetable crops. Some of B. rapa varieties are highly sensitive to high temperature, and thus have very circumscribed growing seasons.
The common symptoms of heat sensitivity (also known as heat intolerance) are leaf etiolation and wilting . Under too-warm conditions, many B. rapa varieties exhibit these traits and stop growing. In recent years, a great deal of attention has been paid to elucidating the mechanisms of heat-sensitivity in B. rapa. High temperature suppresses the production of some chloroplast-specific small RNAs that may function in transcriptional or post-transcriptional regulation. Using RNA and small RNA sequencing datasets, we detected the genome-wide cis-NATs and heat-responsive nat-siRNAs in B. rapa.
Gene models and cis-NATs in B. rapa
In the B. rapa genome v1.1, Wang et al. annotated 39786 gene models, including only coding sequences (CDSs) without un-translated regions (UTRs) . To identify the genome-wide cis-NATs in B. rapa, we performed the RNA sequencing using RNA isolated from B. rapa ssp. chinensis cv. Wut, a heat-sensitive variety, and B. rapa ssp. pekinensis cv. Bre, a less heat-sensitive variety. In the seedlings, 2.77 million and 2.56 million reads were present in Bre and Wut, respectively; and the inflorescence apices yielded 1.80 million and 2.69 million reads in Bre and Wut, respectively (Additional file 1: Table S1).
Overview of B. rapa transcripts assembled through the Tophat-Cufflink pipeline
Gene model union
Different types of cis-NATs in B. rapa
Specific in Bre
Specific in Wut
General in B. rapab
List of pri-miRNA in cis-NATs
Conserved and novel cis-NATs in B. rapa
Using the Arabidopsis genome annotation (TAIR 10 version), we detected 1587 pairs of cis-NAT with overlapping region that was more than 25-nt in Arabidopsis. Based on the homologous gene annotation between Arabidopsis and Brassica, we found that 303 conserved cis-NATs in B. rapa corresponded to 280 cis-NATs in Arabidopsis (Additional file 3: Table S5). 21 cis-NATs in Arabidopsis had two copies cis-NATs in B. rapa, while cis-NAT pair of AT3G12250/AT3G12260 had 3 copies of cis-NATs in B. rapa. Thus, 728 novel cis-NATs were Brassica-specific. Among 150 cis-NATs that generated nat-siRNAs in B. rapa, 47 were conserved in Arabidopsis, revealing that approximately 100 cis-NATs produced nat-siRNAs specifically in B. rapa. In Arabidopsis, Zhang et al. identified 84 cis-NATs that give rise to nat-siRNAs from 21 sRNA libraries . 9 of them existed in B. rapa.
Nat-siRNAs in overlapping region of cis-NATs
To survey genome-wide nat-siRNAs derived from cis-NATs, we constructed and data mined six sRNA libraries. Two were prepared from the seedlings of Bre exposed to biotic stress and four from the seedling of Wut exposed to abiotic stress. For biotic stress, Bre plants were either uninfected (control) or infected by the bacterial strain Erwinia carotovora ssp. carotovora (Ecc), which causes soft rot disease . Wut plants were exposed to either 22°C (Normal temperature, NT) or 46°C (high temperature, HT) for 1 h, with two replicates (NT1, HT1, NT2, and HT2) [26, 28]. In total, we obtained 4.49 million and 4.09 million sRNA reads in the control and bacteria-infected Bre plants, respectively, and 14.67 million, 12.77 million, 11.25 million and 14.61 million reads in HT1, HT1, NT2, and NT2 Wut seedlings, respectively. The abundance of each dataset was normalized to RP10M (reads per 10 million).
Nat-siRNAs responsive to heat stress
The ratios of high-temperature cis-nat-siRNAs to normal-temperature ones derived from cis-NATs
Putative target genes
More cis-NATs and nat-siRNAs in B. rapaafter genome triplication
In this study, we globally identified 1031 cis-NATs and 4846 nat-siRNAs derived from 150 cis-NATs in two varieties of B. rapa. The nat-siRNAs are thought to be processed from overlapping regions of transcribed cis-NATs. The diploid ancestral genome of mesohexaploid B. rapa was closely related to the A. thaliana genome . Comparison of cis-NATs between these two species showed that 303 conserved cis-NATs in B. rapa corresponded to 280 cis-NATs in Arabidopsis. 22 Arabidopsis cis-NATs have two or three copies of homologous cis-NATs in B. rapa. In B. rapa, cis-NATs with more than 2 copies would crosstalk with each other and form trans-NATs. Based on pairwise alignments of transcripts, 47 cis-NATs that produce nat-siRNAs in B. rapa are conserved in Arabidopsis, implying that the two thirds of the cis-NATs in B. rapa generate specific nat-siRNAs. When nat-siRNAs are examined in other subspecies and varieties of B. rapa, more nat-siRNAs from conserved cis-NATs will be detected. The interaction of multiple copies of cis-NATs must be more complex, but should not bring chaos, because the individual variants with chaos are died out during evolution.
The nat-siRNAs in coding sequences are more conserved than those in other regions as described in Arabidopsis lyrata. The roles of conserved cis-NATs and nat-siRNAs may be general in development events or response to environment stimuli of plants, whereas those of the novel cis-NATs in B. rapa should be specific. Interestingly, some Brassica-specific cis-NATs and nat-siRNAs are more than two. These overlapping-sequences are differentiated over time, since many SNPs has been identified in different Brassica crops. Possibly, two copies of an Arabidopsis cis-NAT in B. rapa occurs when they are trans-NATs (at different loci). Our study is focused on cis-NATs rather than trans-NATs, which are more complex. It is not known whether cis-NATs and trans-NATs are different in regulation of target genes.
Previous work in Arabidopsis indicated that nat-siRNAs could target and cleave one of the cis-NAT at the posttranscriptional level . Heat-induced nat-siRNAs generated from an up-regulated transcript may function in repressing its targets, which should be cleared under heat stress. The nat-siRNAs could be generated from both cis-NATs and trans-NATs, and targets to the transcripts with high sequence complimentarity. Because B. rapa has multiple homolog genes, T-DNA insertion could knock-out only one copy. However, over-expression of a single cis-NAT could knock-down several homologous targets, thus, suggesting potential application of nat-siRNAs from cis-NATs for improving heat-resistance.
Strand bias in heat-responsive cis-NATs and nat-siRNAs
Nat-siRNAs has been shown to response to environment stimuli such as salt stress and biotic stress . In plants, nat-siRNASRO5 is induced by salinity , while nat-siRNAATGB2 only accumulates in response to bacterial pathogen infection . However, which nat-siRNAs are involved in heat stress is largely unknown, even in Arabidopsis. We identified 12 cis-NATs that respond to heat stress, with strand bias.
The nat-siRNAs derived from four conserved cis-NATs are conserved in Arabidopsis. Like the salt-induced gene SRO5 which forms a double helix with its cis-NAT pair P5CDH, Bra018216 is induced by heat stress, and is complementary to Bra018217 to produce dispersed siRNAs. However, the length of nat-siRNAs from Bra018216/Bra018217 ranged from 20–28 nt rather than 21 or 24 nt. Nat-siRNAs of 20–22 nt are generated by DCL1, whereas the 23–28-nt nat-siRNAs are DCL3-dependent . The nat-siRNAs derived from Bra018216 may repress Bra018217 expression. Whether over-expression of Bra018216 would improve the heat resistance of B. rapa remains to be investigated.
Potential roles of heat-responsive cis-NATs and nat-siRNAs
Eight of the miRNA precursors reported are cis-NATs that overlapp with coding genes. In a previous study, we have identified nine miRNAs that responded to heat stress in B. rapa. Among them, miR398a and miR398b were very sensitive to heat stress, and MIR398b precursor was also decreased under heat stress in B. rapa. Heat stress induction of miR398 triggers a regulatory loop that is critical for thermotolerance in Arabidopsis. In this study, two miR398b precursors were found to overlaps with their adjacent genes. The question arises whether these adjacent genes are involved in the regulation of miR398–mediated thermotolerance.
Heat stress disturbs cellular homeostasis. The accumulation of heat shock proteins under the control of heat stress transcription factors plays a central role in heat resistance . In tobacco plants, genetic engineering of the biosynthesis of glycinebetaine enhances thermotolerance of photosystem II , and chloroplastic NAD(P)H dehydrogenase in tobacco leaves alleviates the oxidative damage caused by temperature stress . Three cis-NATs that give rise to heat-responsive nat-siRNA encoded HSP17.4 (small heat shock protein), LHCB3 (a component of the main light harvesting chlorophyll a/b-protein complex of Photosystem II), and NDF4 (a novel subunit of the chloroplast NAD(P)H dehydrogenase complex), meaning that nat-siRNA from those cis-NATs may play important roles in heat resistance.
The present work is based on putative identifications using bioinformatics tools. Northern blots of more nat-siRNAs are necessary to confirm the difference in their accumulation between normal and high temperature. More importantly, the direct evidence is dependent on silencing of nat-siRNA to the target genes in the transgenic plants. Therefore, a great attention should be paid to transfer the nat-siRNAs into crops to verify their usefulness for increase in heat-resistance.
In addition to nucleus, the chloroplast is an important organelle that generates sRNAs. Many members of chloroplast sRNA families are highly sensitive to heat stress, and some silence target genes. To address the roles of heat-responsive nat-siRNAs in plant heat resistance, we plan to compare the gene expression patterns of heat-sensitive Wut with the less heat-sensitive Bre. Analyses of the differentially-expressed nat-siRNAs could provide insight into the molecular mechanism of nat-siRNA-mediated responses. Ultimately, these nat-siRNAs may be useful for genetic improvement of the heat resistance in Chinese cabbage and other important crops.
In two varieties of B. rapa, we identified 1031 cis-NATs, 150 of which gave rise to 4846 nat-siRNAs. Of these, 303 conserved cis-NATs corresponded to 280 cis-NATs in Arabidopsis, indicating that 728 novel cis-NATs were Brassica-specific. The nat-siRNAs derived from 12 cis-NATs responded to heat stress and most exhibited strand bias. Our work was the first genome-wide analysis of cis-NATs and heat-responsive nat-siRNAs in B. rapa; these sRNAs are potentially useful for genetic improvement of heat tolerance of B. rapa and other crops.
Plant materials and sequencing
Heading Chinese cabbage (B. rapa ssp. pekinensis cv. Bre) and non-heading Chinese cabbage (B. rapa ssp. chinensis cv. Wut) were used in this study. For RNA sequencing, the seedling (3 weeks old) and inflorescence apices (IA) (2 months old) of Bre and Wut were sampled. Total RNA was extracted with TRIzol (Invitrogen, Carlsbad, CA, USA) and treated with DNase I (Takara, Dalian, China) to remove DNA contamination. Two RNA samples prepared from seedling of Bre and Wut were sent to BGI Shenzhen (Beijing, China) and two RNA samples from IA were sent to macrogen company (Seoul, South Korea) for high throughput cDNA sequencing. For sRNA sequencing, 7-day-old seedlings of Bre were root-inoculated with the bacterial strain (Erwinia carotovora subsp. carotovora), while seedlings inoculated with sterile water served as mock controls; RNA samples were prepared 2-weeks after inoculation . Three week old seedlings of Wut were exposed to 22°C (NT) or 46°C (HT) for 1 h, with two biological replicates (NT1, NT2, HT1, and HT2) . RNA samples were prepared using the Alternative v1.5 Protocol (Illumina, 2009), and sRNA sequencing was performed using Illumina GAII sequencer and mirVana™ miRNA Isolation Kit (Ambion, Carlsbad, CA, USA).
Small RNAs were isolated using mirVana™ miRNA Isolation Kit (Ambion, Inc), and sRNA sequencing was performed using Illumina GAII sequencer. Although the samples for RNA sequencing and small RNA sequencing were not from the same seedlings, the heat-treated samples for sRNA sequencing were 3-week-old plants of Wut, consistent with the development stages RNA sequencing samples. The RNA-sequences were used to obtain cis-NATs and sRNA annotation, and we focused on comparing the expression of nat-siRNAs between samples with and without heat treatment.
Alignment and gene annotation
A total of 98291786 paired-end reads were obtained from 4 RNA samples via Illumina sequencing. Using the Tophat-Cufflink pipeline , the reads were mapped to the reference genome v1.1 of B. rapa by the short read aligner Bowtie, and the transcripts were further assembled by Cufflink with default parameter . Cuffcompare program was used to compare the transcripts with reference gene models (CDS), and the longest of each detected transcript with an extended UTR was annotated as a novel gene models. Conserved and Brassica-specific miRNA precursors were locally blasted with Brasscia genome and the best hit positions were annotated with the gff3 format. Raw sequence reads of sRNA were parsed to remove 3′-adaptors, and the unique sequences of length 17–36 nt were mapped to the B. rapa by SOAP2 software with fewer than two mismatches.
Identification of cis-NATs and nat-siRNAs
Using the Brassica novel genome annotations containing miRNA precursors and genes with the longest extended UTR in Brassica, pairs of genes that overlapped by more than 25 nt, were shorter than 2000 nt, and were transcribed from the opposite DNA strand were regarded as cis-NATs. Small RNAs from overlapping region of cis-NATs that satisfied the following standards were considered to be potential nat-siRNAs: (1) perfect matches with the reference genome; (2) the length of 20–28 nt; and (3) at least 5 reads per 10 million at least in one sRNA library.
Analysis of strand bias of nat-siRNAs derived from cis-NATs
where N1 represents the total sRNA read number in the seedlings without heat treatment, while N2 represents number with heat treatment; x represents the abundance of nat-siRNA in seedlings without heat treatment, and y represents abundance in seedlings with heat treatment.
Identification of conserved cis-NATs between B. rapaand Arabidopsis
Arabidopsis homologs to the global B. rapa cis-NATs were selected from the homologous gene table of two species. Genome-wide cis-NATs in Arabidopsis were identified using the Arabidopsis genome annotation (TAIR version 10) as described above for B. rapa The homologous cis-NATs were considered to be conserved cis-NATs (Additional file 3: Table S5).
Differential expression analysis of heat-responsive nat-siRNAs
The Bayesian test method was used to determine the expression differences between the two temperature conditions (NT and HT) by compariing tag counts generated from digital expression analyses . In both replicates, the ratios of total reads of nat-siRNAs from cis-NATs in the two conditions (HT1/NT1 and HT2/NT2) were more than 2 (or less than 0.5) and the p-value <0.01, so these differences were considered significant.
Total RNA was extracted with TRIzol (Invitrogen) and treated with DNase I (Takara) to remove DNA contamination. Approximately, 4 μg of RNA was used for reverse transcription with oligo-dT primers. Real-time PCR was performed using specific pairs of primers (Additional file 7: Table S7). The comparative threshold cycle (Ct) method was used to determine relative transcript levels in real-time PCR (MyiQ2, Two-Colors Real-time PCR Detection System, Bio-Rad, Hercules, CA, USA). BrcACT4 of B. rapa, which is homologous to Arabidopsis ACT4 encoding actin protein, was used as an internal control. Three biological replicates and three technological replicates were performed.
Small RNA purification and Northern blot
Small RNA purification was performed referring to protocol of Hamilton and Baulcombe  with minor modifications. Coding sequence of Bra018216 was amplified with primer pairs Bra018216-8S and Bra018216-337A (Additional file 7: Table S7), and single–stranded RNA probes were transcribed from antisense transcripts of Bra018216 using T7 RNA polymerase with digoxin-labeled uridine triphosphate (Dig-11-dUTP). 30–50 μg RNA was separated on 19% polyacylamide denaturing gels, and transformed to Hybond membrane for 14 h at 28 mA. After cross-linking for 4 min with UV irradiation and 80°C for 2 h, the Hybond membrane was hybridized with digoxin-labeled probe at 37°C overnight, and was washed twice at 37°C with 2× SSC and 0.2% SDS for 15 min. Then, the membrane was incubated with blocking reagent for 30 min, and reacted with Anti-Digoxigenin-AP Fab fragment, and again was washed with 2× SSC and 0.2% SDS for 15 min. At last, the membrane was equilibrated with equilibration buffer, soaked in CDP-Star solution, and exposed to x-ray file (Fuji film). Blots were also probed with a biotin-marked DNA probe complementary to U6 as an internal control, using the Thermo scientific Kit.
Availability of supporting data
The raw data has been submitted to the NCBI Sequence Read Archive (SRA) (http://www.ncbi.nlm.nih.gov/sra). The SRA accessions of 4 RNA sequencing experiments are SRX323438, SRX323448, SRX323442 and SRX323460.
- B. rapa:
Contained coding sequence
cis-natural antisense transcripts
Erwinia carotovora subsp. carotovora
- Intronic miRNAs:
NAT-derived small interfering RNAs
Natural antisense transcripts
Reads per 10 million
trans-acting small interfering RNAs
This work is supported by National Basic Research Program of China (Grant No. 2012CB113903) and Natural Science Foundation of China (Grant No. 30730053).
- Zhang Y, Liu XS, Liu QR, Wei L: Genome-wide in silico identification and analysis of cis natural antisense transcripts (cis-NATs) in ten species. Nucleic Acids Res. 2006, 34: 3465-3475. 10.1093/nar/gkl473.PubMedPubMed CentralView ArticleGoogle Scholar
- Katayama S, Tomaru Y, Kasukawa T, Waki K, Nakanishi M, Nakamura M, Nishida H, Yap CC, Suzuki M, Kawai J, et al: Antisense transcription in the mammalian transcriptome. Science. 2002, 309: 1564-1566.Google Scholar
- Chen JJ, Sun M, Kent WJ, Huang XQ, Xie HQ, Wang WQ, Zhou GL, Shi RZ, Rowley JD: Over 20% of human transcripts might form sense-antisense pairs. Nucleic Acids Res. 2004, 32: 4812-4820. 10.1093/nar/gkh818.PubMedPubMed CentralView ArticleGoogle Scholar
- Okazaki Y, Furuno M, Kasukawa T, Adachi J, Bono H, Kondo S, Nikaido I, Osato N, Saito R, Suzuki H, et al: Analysis of the mouse transcriptome based on functional annotation of 60,770 full-length cDNAs. Nature. 2002, 420: 563-573. 10.1038/nature01266.PubMedView ArticleGoogle Scholar
- Misra S, Crosby MA, Mungall CJ, Matthews BB, Campbell KS, Hradecky P, Huang Y, Kaminker JS, Millburn GH, Prochnik SE, et al: Annotation of the Drosophila melanogaster euchromatic genome: a systematic review. Genome Biol. 2002, 3 (12): R83.View ArticleGoogle Scholar
- Wang XJ, Gaasterland T, Chua NH: Genome-wide prediction and identification of cis-natural antisense transcripts in Arabidopsis thaliana. Genome Biol. 2005, 6 (4): R30. 10.1186/gb-2005-6-4-r30.PubMedPubMed CentralView ArticleGoogle Scholar
- Osato N, Yamada H, Satoh K, Ooka H, Yamamoto M, Suzuki K, Kawai J, Carninci P, Ohtomo Y, Murakami K, et al: Antisense transcripts with rice full-length cDNAs. Genome Biol. 2003, 5: R5. 10.1186/gb-2003-5-1-r5.PubMedPubMed CentralView ArticleGoogle Scholar
- Munroe SH, Lazar MA: Inhibition of c-erbA mRNA splicing by a naturally occurring antisense RNA. J Biol Chem. 1991, 266: 22083-22086.PubMedGoogle Scholar
- Tufarelli C, Stanley JA, Garrick D, Sharpe JA, Ayyub H, Wood WG, Higgs DR: Transcription of antisense RNA leading to gene silencing and methylation as a novel cause of human genetic disease. Nat Genet. 2003, 34: 157-165. 10.1038/ng1157.PubMedView ArticleGoogle Scholar
- Moore T, Constancia M, Zubair M, Bailleul B, Feil R, Sasaki H, Reik W: Multiple imprinted sense and antisense transcripts, differential methylation and tandem repeats in a putative imprinting control region upstream of mouse Igf2. Proc Natl Acad Sci U S A. 1997, 94: 12509-12514. 10.1073/pnas.94.23.12509.PubMedPubMed CentralView ArticleGoogle Scholar
- Peters NT, Rohrbach JA, Zalewski BA, Byrkett CM, Vaughn JC: RNA editing and regulation of Drosophila 4f-rnp expression by sas-10 antisense read through mRNA transcripts. RNA. 2003, 9: 698-710. 10.1261/rna.2120703.PubMedPubMed CentralView ArticleGoogle Scholar
- Borsani O, Zhu JH, Verslues PE, Sunkar R, Zhu JK: Endogenous siRNAs derived from a pair of natural cis-antisense transcripts regulate salt tolerance in Arabidopsis. Cell. 2005, 123: 1279-1291. 10.1016/j.cell.2005.11.035.PubMedPubMed CentralView ArticleGoogle Scholar
- Katiyar-Agarwal S, Morgan R, Dahlbeck D, Borsani O, Villegas A, Zhu JK, Staskawicz BJ, Jin HL: A pathogen-inducible endogenous siRNA in plant immunity. Proc Natl Acad Sci U S A. 2006, 103: 18002-18007. 10.1073/pnas.0608258103.PubMedPubMed CentralView ArticleGoogle Scholar
- Zhou X, Sunkar R, Jin H, Zhu JK, Zhang W: Genome-wide identification and analysis of small RNAs originated from natural antisense transcripts in Oryza sativa. Genome Res. 2009, 19 (1): 70-78.PubMedPubMed CentralView ArticleGoogle Scholar
- Lu T, Zhu C, Lu G, Guo Y, Zhou Y, Zhang Z, Zhao Y, Li W, Lu Y, Tang W, et al: Strand-specific RNA-seq reveals widespread occurrence of novel cis-natural anti sense transcripts in rice. BMC Genomics. 2012, 13: 721. 10.1186/1471-2164-13-721.PubMedPubMed CentralView ArticleGoogle Scholar
- Zhang X, Xia J, Lii YE, Barrera-Figueroa BE, Zhou X, Gao S, Lu L, Niu D, Chen Z, Leung C, et al: Genome-wide analysis of plant nat-siRNAs reveals insights into their distribution, biogenesis and function. Genome Biol. 2012, 13 (3): R20. 10.1186/gb-2012-13-3-r20.PubMedPubMed CentralView ArticleGoogle Scholar
- Jamalkandi SA, Masoudi-Nejad A: Reconstruction of Arabidopsis thaliana fully integrated small RNA pathway. Funct Integr Genomics. 2009, 9: 419-432. 10.1007/s10142-009-0141-z.PubMedView ArticleGoogle Scholar
- Kurihara Y, Takashi Y, Watanabe Y: The interaction between DCL1 and HYL1 is important for efficient and precise processing of pri-miRNA in plant microRNA biogenesis. RNA. 2006, 12: 206-212.PubMedPubMed CentralView ArticleGoogle Scholar
- LI SB, Liu L, Zhuang XH, Yu Y, Liu X, Cui X, Ji LJ, Pan ZQ, Cao XF, Mo BX, et al: MicroRNAs inhibit the translation of target mRNAs on the endoplasmic reticulum in Arabidopsis. Cell. 2013, 153: 562-574. 10.1016/j.cell.2013.04.005.PubMedPubMed CentralView ArticleGoogle Scholar
- Chen X: Small RNAs and their roles in plant development. Annu Rev Cell Dev Biol. 2009, 25: 21-44. 10.1146/annurev.cellbio.042308.113417.PubMedView ArticleGoogle Scholar
- Shukla LI, Chinnusamy V, Sunkar R: The role of microRNAs and other endogenous small RNAs in plant stress responses. Biochim Biophys Acta. 2008, 1779: 743-748. 10.1016/j.bbagrm.2008.04.004.PubMedView ArticleGoogle Scholar
- Kim YK, Kim VN: Processing of intronic microRNAs. EMBO J. 2007, 26 (3): 775-783. 10.1038/sj.emboj.7601512.PubMedPubMed CentralView ArticleGoogle Scholar
- Ron M, Saez MA, Williams LE, Fletcher JC, McCormick S: Proper regulation of a sperm-specific cis-nat-siRNA is essential for double fertilization in Arabidopsis. Genes Dev. 2010, 24: 1010-1021. 10.1101/gad.1882810.PubMedPubMed CentralView ArticleGoogle Scholar
- Snowdon RJ: Cytogenetics and genome analysis in Brassica crops. Chromosome Res. 2007, 15: 85-95. 10.1007/s10577-006-1105-y.PubMedView ArticleGoogle Scholar
- Cheng F, Mandáková T, Wu J, Xie Q, Lysak MA, Wang X: Deciphering the diploid ancestral genome of the mesohexaploid Brassica rapa. Plant Cell. 2013, 25 (5): 1541-1554. 10.1105/tpc.113.110486.PubMedPubMed CentralView ArticleGoogle Scholar
- Yu X, Wang H, Lu Y, de Ruiter M, Cariaso M, Prins M, van Tunen A, He Y: Identification of conserved and novel microRNAs that are responsive to heat stress in Brassica rapa. J Exp Bot. 2012, 63: 1025-1038. 10.1093/jxb/err337.PubMedPubMed CentralView ArticleGoogle Scholar
- Kim B, Yu HJ, Park SG, Shin JY, Oh M, Kim N, Mun JH: Identification and profiling of novel microRNAs in the Brassica rapa genome based on small RNA deep sequencing. BMC Plant Biol. 2012, 12: 218. 10.1186/1471-2229-12-218.PubMedPubMed CentralView ArticleGoogle Scholar
- Wang L, Yu X, Wang H, Lu YZ, de Ruiter M, Prins M, He YK: A novel class of heat-responsive small RNAs derived from the chloroplast genome of Chinese cabbage (Brassica rapa). BMC Genomics. 2011, 12: 289. 10.1186/1471-2164-12-289.PubMedPubMed CentralView ArticleGoogle Scholar
- Wang X, Wang H, Wang J, Sun R, Wu J, Liu S, Bai Y, Mun JH, Bancroft I, Cheng F, et al: The genome of the mesopolyploid crop species Brassica rapa. Nat Genet. 2011, 43: 1035-1039. 10.1038/ng.919.PubMedView ArticleGoogle Scholar
- Trapnell C, Roberts A, Goff L, Pertea G, Kim D, Kelley DR, Pimentel H, Salzberg SL, Rinn JL, Pachter L: Differential gene and transcript expression analysis of RNA-seq experiments with TopHat and Cufflinks. Nat Protoc. 2012, 7 (3): 562-578. 10.1038/nprot.2012.016.PubMedPubMed CentralView ArticleGoogle Scholar
- Sun CB, Du XM, He YK: A novel method for constructing pathogen-regulated small RNA cDNA library. Biochem Biophys Res Commun. 2010, 397 (3): 532-536. 10.1016/j.bbrc.2010.05.151.PubMedView ArticleGoogle Scholar
- Kilian J, Whitehead D, Horak J, Wanke D, Weinl S, Batistic O, D’Angelo Bornberg-Bauer E, Kudla J, Harter K: The AtGenExpress global stress expression data set: protocols, evaluation and model data analysis of UV-B light, drought and cold stress responses. Plant J. 2007, 50: 347-363. 10.1111/j.1365-313X.2007.03052.x.PubMedView ArticleGoogle Scholar
- Ma Z, Coruh C, Axtell MJ: Arabidopsis lyrata small RNAs: transient MIRNA and small interfering RNA loci within the Arabidopsis genus. Plant Cell. 2010, 22 (4): 1090-1103. 10.1105/tpc.110.073882.PubMedPubMed CentralView ArticleGoogle Scholar
- Zhang X, Lii Y, Wu Z, Polishko A, Zhang H, Chinnusamy V, Lonardi S, Zhu JK, Liu R, Jin H: Mechanisms of small RNA generation from cis-NATs in response to environmental and developmental cues. Mol Plant. 2013, 6: 704-715. 10.1093/mp/sst051.PubMedPubMed CentralView ArticleGoogle Scholar
- Guan Q, Lu X, Zeng H, Zhang Y, Zhu J: Heat stress induction of miR398 triggers a regulatory loop that is critical for thermotolerance in Arabidopsis. Plant J. 2013, 74: 840-851. 10.1111/tpj.12169.PubMedView ArticleGoogle Scholar
- Kotak S, Larkindale J, Lee U, von Koskull-Doring P, Vierling E, Scharf KD: Complexity of the heat stress response in plants. Curr Opin Plant Biol. 2007, 10: 310-316. 10.1016/j.pbi.2007.04.011.PubMedView ArticleGoogle Scholar
- Yang X, Wen X, Gong H, Lu Q, Yang Z, Tang Y, Liang Z, Lu C: Genetic engineering of the biosynthesis of glycinebetaine enhances thermotolerance of photosystem II in tobacco plants. Planta. 2007, 225: 719-733. 10.1007/s00425-006-0380-3.PubMedView ArticleGoogle Scholar
- Wang P, Duan W, Takabayashi A, Endo T, Shikanai T, Ye JY, Mi H: Chloroplastic NAD(P)H dehydrogenase in tobacco leaves functions in alleviation of oxidative damage caused by temperature stress. Plant Physiol. 2006, 141: 465-474. 10.1104/pp.105.070490.PubMedPubMed CentralView ArticleGoogle Scholar
- Audic S, Claverie JM: The significance of digital gene expression profiles. Genome Res. 1997, 7: 986-995.PubMedGoogle Scholar
- Hamilton A, Baulcombe D: A novel species of small antisense RNA in post-transcriptional gene silencing. Science. 1999, 286: 950-952. 10.1126/science.286.5441.950.PubMedView ArticleGoogle Scholar
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