Abstract
RNAi mediated gene silencing demonstrated to serve as a defence mechanism against abiotic stress. Some endogenous small RNAs (microRNA and siRNA) have emerged as important players in plant abiotic stress response. Drought and salinity are the major environmental stresses that limit the agricultural food production. miRNA involved in drought and salinity stress response, including ABA response, auxin signalling, osmoprotection and antioxidant defence by downregulating the response target gene. It is observed that some of the microRNAs are upregulated or downregulated in response to drought and salt stress. We reviewed that miR167, miR393, mir474, miR169g are upregulated whereas miR168, miR396, miR397 are downregulated in rice plant during drought stress. Moreover, our detail categorical analysis on the basis of mechanism of action found that miRNA involved in drought stress was 28% in ABA signalling and response, 14.2% in auxin signalling, 9.52% in miRNA processing, 14.2% in cell growth, 9.52% in antioxidant defence, 4.76% in CO2 fixation and 9.52% in osmotic adjustment. Similarly, miRNA involved in salinity stress was 5.8% in auxin signalling, 23.5% in vegetative phase change and root, shoot, leaf and vascular development, 11.76% in gynoecium and stamens development, 8.82% in metabolic adaptation, 2.74% in early embryogenesis and 41.17% not known. Importantly, some common miRNAs such as miR159, miR167, miR169, miR393 and miR397 play an important role in both drought and salinity stress conditions. Here, in this review, we mainly focused on the current status of miRNAs, mechanism of action and their regulatory network during drought and salinity stress in plants.
Highlights
Agriculture productivity is negatively affected due to various abiotic factors
There are two small RNA in the RNA interference (RNAi) pathway, a small interfering RNA and a micro RNA. miRNA are similar to siRNA in many respect as they originate from double stranded structure, the size of the miRNA is 20 to 30 bp and both are proceed by DICER or DICER like enzyme (DCL1, DCL2)
In Vigna unguiculata miR393 were upregulated in drought stress and target the TAS3-Auxin response factors (ARFs) that play an important role in Auxin signalling and lateral root development in plant [69]
Summary
Agriculture productivity is negatively affected due to various abiotic factors. It is well understood that crops tolerating environmental stresses will be in high demand, as the world is getting hotter and drier day by day [1]. Drought and salinity stress tolerance and adaptation in rice plants have been improved by engineering various transcription factors, genes related to signalling pathway, compatible solutes and accumulation of antioxidants. The importance of many genes related to several pathways has been clearly elucidated in a review of stress tolerance mechanisms and use of transgenic technology in agriculture for developing abiotic stress tolerant crop plants [3]. It is very essential to evaluate the exact role of specific transcription factor(s) or gene(s) and genetic manipulation for the crop improvement. The duplex 21-nucleotide is the form, commonly called as small interfering RNA (siRNA), which is responsible for degradation of mRNA, leading to suppression or alteration of the gene expression [5]. This review focused on the landmark in RNAi discovery, its component and mechanism of action and its role in abiotic stress tolerance in plants, basically drought and salt stress tolerance
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