Biogenesis to functional significance of microRNAs under drought stress in rice: Recent advances and future perspectives

The 21st century is considered to be an era of global climate change while recurring drought causes severe yield losses, challenging crop production, and raising serious concerns about sustainable food production/security. MicroRNAs (miRNAs) have emerged as a new candidate for improving/modulating developmental processes in plants, including grain yield, productivity, and response to various abiotic stresses such as drought, heat, and salinity. miRNA can regulate expression of genes either by translation repression or by mRNA cleavage. To regulate expression of gene(s), it targets transcription factors and/or the stress-associated gene responsible for enhancing adaptive potential of plant. For example, miR159-MYB, miR169-NFYA, and miR160-ARF are wellknown conserved miRNA-target combinations which regulate drought stress responses in plants. Stress- responsive miRNAs have been demonstrated to modulate physiological, biochemical, and molecular processes, thus serving as key regulators for genetic modification of plants for enhanced drought tolerance. The present review provides insights on the miRNAs involved in drought stress response in rice and their role in regulation of critically important biological processes including photosynthesis, respiration, phytohormone signaling, osmotic stress, and senescence. In addition, the current limitations in using miRNA-based strategies and future perspectives have also been discussed. We envisage that this review would help understanding the role of miRNAs as a part of gene regulatory network for genetic improvement of rice towards enhancing yielding potential under water-deficiency stress.