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In Medicago truncatula, water deficit modulates the transcript accumulation of components of small RNA pathways.

ABSTRACT: BACKGROUND: Small RNAs (sRNAs) are 20-24 nucleotide (nt) RNAs and are involved in plant development and response to abiotic stresses. Plants have several sRNA pathways implicated in the transcriptional and post-transcriptional silencing of gene expression. Two key enzyme families common to all pathways are the Dicer-like (DCL) proteins involved in sRNAs maturation and the Argonautes (AGOs) involved in the targeting and functional action of sRNAs. Post-transcriptional silencing mediated by AGOs may occur by cleavage or translational repression of target mRNA's, while transcriptional silencing may be controlled by DNA methylation and chromatin remodeling. Thus far, these gene families have not been characterized in legumes, nor has their involvement in adaptation to water deficit been studied. RESULTS: A bioinformatic search in Medicago truncatula genome databases, using Arabidopsis thaliana AGO and DCL cDNA and protein sequences, identified three sequences encoding for putative Dicer-like genes and twelve sequences encoding for putative Argonaute genes. Under water deficit conditions and mainly in roots, MtDCL1 and MtAGO1, two enzymes probably involved in the processing and activation of microRNAs (miRNAs), increased their transcript levels. mir162 which target DCL1 mRNA and mir168 which target AGO1 mRNA reduced their expression in the roots of plants subjected to water deficit. Three putative genes, MtDCL3, MtAGO4b and MtAGO4c probably involved in DNA methylation mechanisms, increased their mRNA levels. However, the mRNA levels of MtAGO6 reduced, which probably encodes a protein with functions similar to MtAGO4. MtAGO7 mRNA levels increased and possibly encodes a protein involved in the production of trans-acting small interfering RNAs. The transcript abundance of MtAGO12a, MtAGO12b and MtAGO12c reduced under water deprivation. Plants recovered from water deprivation reacquire the mRNA levels of the controls. CONCLUSIONS: Our work demonstrates that in M. truncatula the transcript accumulation of the components of small RNA pathways is being modulated under water deficit. This shows that the transcriptional and post-transcriptional control of gene expression mediated by sRNAs is probably involved in plant adaptation to abiotic environmental changes. In the future this will allow the manipulation of these pathways providing a more efficient response of legumes towards water shortage.

SUBMITTER: Capitao C

PROVIDER: S-EPMC3098777 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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In Medicago truncatula, water deficit modulates the transcript accumulation of components of small RNA pathways.

Capitão Cláudio C Paiva Jorge A P JA Santos Dulce M DM Fevereiro Pedro P

BMC plant biology 20110510

<h4>Background</h4>Small RNAs (sRNAs) are 20-24 nucleotide (nt) RNAs and are involved in plant development and response to abiotic stresses. Plants have several sRNA pathways implicated in the transcriptional and post-transcriptional silencing of gene expression. Two key enzyme families common to all pathways are the Dicer-like (DCL) proteins involved in sRNAs maturation and the Argonautes (AGOs) involved in the targeting and functional action of sRNAs. Post-transcriptional silencing mediated by ...[more]

PMID: 21569262

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Project description:Mercury (Hg) contamination is increasing worldwide in both wild ecosystems and agricultural soils due to natural processes, but mostly to anthropic activities. The molecular mechanisms involved in Hg toxicity and tolerance in plants have been extensively studied; however, the role of flavonoids in response to Hg stress remains to be investigated. We conducted a metabolomic study to analyze the changes induced at the secondary metabolite level in three Hg-tolerant and one Hg-sensitive Medicago truncatula cultivars. A total of 46 flavonoid compounds, classified into five different flavonoid families: anthocyanidins, flavones, isoflavones, pterocarpan flavonoids, and flavanones, along with their respective glycoconjugate derivatives, were identified in leaf and root tissues. The synthesis of free isoflavones, followed by monoglycosylation and further malonylation was shown to be characteristic of root samples, whereas higher glycosylation, followed by further acylation with coumaric and ferulic acid was characteristic of leaf tissues. While minor changes were observed in leaves, significant quantitative changes could be observed in roots upon Hg treatment. Some flavonoids were strongly upregulated in roots, including malonylglucosides of biochanin A, formononetin and medicarpin, and aglycones biochanin, daidzein, and irisolidone. Hg tolerance appeared to be mainly associated to the accumulation of formononetin MalGlc, tricin GlcAGlcA, and afrormosin Glc II in leaves, whereas aglycone accumulation was associated with tolerance to Hg stress in roots. The results evidence the alteration of the flavonoid metabolic profile and their glycosylation processes in response to Hg stress. However, notable differences existed between varieties, both in the basal metabolic profile and in the response to treatment with Hg. Overall, we observed an increase in flavonoid production in response to Hg stress, and Hg tolerance appeared to be associated to a characteristic glycosylation pattern in roots, associated with the accumulation of aglycones and monoglycosylated flavonoids. The findings are discussed in the context of the flavonoid biosynthetic pathway to provide a better understanding of the role of these secondary metabolites in the response and tolerance to Hg stress in M. truncatula.

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In Medicago truncatula, water deficit modulates the transcript accumulation of components of small RNA pathways.

Publications

In Medicago truncatula, water deficit modulates the transcript accumulation of components of small RNA pathways.

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