Abstract
The microRNAs (miRNAs) are small (20–24 nt) sized, non-coding, single stranded riboregulator RNAs abundant in higher organisms. Recent findings have established that plants assign miRNAs as critical post-transcriptional regulators of gene expression in sequence-specific manner to respond to numerous abiotic stresses they face during their growth cycle. These small RNAs regulate gene expression via translational inhibition. Usually, stress induced miRNAs downregulate their target mRNAs, whereas, their downregulation leads to accumulation and function of positive regulators. In the past decade, investigations were mainly aimed to identify plant miRNAs, responsive to individual or multiple environmental factors, profiling their expression patterns and recognizing their roles in stress responses and tolerance. Altered expressions of miRNAs implicated in plant growth and development have been reported in several plant species subjected to abiotic stress conditions such as drought, salinity, extreme temperatures, nutrient deprivation, and heavy metals. These findings indicate that miRNAs may hold the key as potential targets for genetic manipulations to engineer abiotic stress tolerance in crop plants. This review is aimed to provide recent updates on plant miRNAs, their biogenesis and functions, target prediction and identification, computational tools and databases available for plant miRNAs, and their roles in abiotic stress-responses and adaptive mechanisms in major crop plants. Besides, the recent case studies for overexpressing the selected miRNAs for miRNA-mediated enhanced abiotic stress tolerance of transgenic plants have been discussed.
Highlights
Plants being sessile organisms, persistently face adverse environmental perturbations termed as abiotic stresses, most important being drought, soil salinity, extreme temperatures, and heavy metals
High throughput sequencing and computational approaches have been used in recent year for identifying a large number of stress-related miRNAs. These findings indicate that miRNAs might serve as potential targets for genetic manipulations to engineer abiotic stress tolerance in plants
We summarize recent updates on plant miRNAs, their biogenesis, target-genes, and their regulatory roles in abiotic stress-responses and adaptive mechanisms deciphered in major crop plants
Summary
Persistently face adverse environmental perturbations termed as abiotic stresses, most important being drought, soil salinity, extreme temperatures, and heavy metals. Plants up-regulate the protective genes while down-regulating the negative regulators. Several protein-coding genes have been recognized in recent years for controlling plant responses to abiotic stresses; our knowledge on the regulatory mechanisms involved in this response are still limited and necessitates transformative tools to adapt crops to harsh environments (Zhang and Wang, 2015). These posttranscriptional regulations are pivotal for plants to restore and re-establish their cellular homeostasis during and recovery from stress phases, respectively (Sunkar et al, 2012)
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