Regulation of micrornas during biotic and abiotic stress

MicroRNAs (miRNAs) are short non-coding RNAs approximately 22 nucleotides play key roles in fundamental cellular processes, comprising how cells react to changes in environment or, stress. Stress is the state when cells deviate from the current situation due to sudden environmental changes or frequent fluctuations in environmental factors. Apart from the cellular concentration of miRNAs, the target gene repression level is also dependent on the concentration of mRNA target relative to the miRNA. From the previous studies it is seen that many aberrant expression of many miRNAs is induced by abiotic stressors so that miRNAs can be used as a new target for genetically improving plant tolerance to many stress. miRNAs respond to environmental stress mainly tissue and genotype-dependent manner. During abiotic stress, miRNAs function by regulating target genes within the miRNA-target gene network and by controlling signalling pathways and root development. In this review, we revisit the processing of microRNAs in animals and plants, history of miRNAs and condense recent findings in miRNA biogenesis and microRNAs involved in biotic and abiotic stress.