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Climate changes and environmental stresses have significant implications on global crop production and necessitate developing crops that can withstand an array of climate changes and environmental perturbations such as irregular water-supplies leading to drought or water-logging, hyper soil-salinity, extreme and variable temperatures, ultraviolet radiations and metal stress. Plants have intricate molecular mechanisms to cope with these dynamic environmental changes, one of the most common and effective being the reprogramming of expression of stress-responsive genes. Plant microRNAs (miRNAs) have emerged as key post-transcriptional and translational regulators of gene-expression for modulation of stress implications. Recent reports are establishing their key roles in epigenetic regulations of stress/adaptive responses as well as in providing plants genome-stability. Several stress responsive miRNAs are being identified from different crop plants and miRNA-driven RNA-interference (RNAi) is turning into a technology of choice for improving crop traits and providing phenotypic plasticity in challenging environments. Here we presents a perspective review on exploration of miRNAs as potent targets for engineering crops that can withstand multi-stress environments via loss-/gain-of-function approaches. This review also shed a light on potential roles plant miRNAs play in genome-stability and their emergence as potent target for genome-editing. Current knowledge on plant miRNAs, their biogenesis, function, their targets, and latest developments in bioinformatics approaches for plant miRNAs are discussed. Though there are recent reviews discussing primarily the individual miRNAs responsive to single stress factors, however, considering practical limitation of this approach, special emphasis is given in this review on miRNAs involved in responses and adaptation of plants to multi-stress environments including at epigenetic and/or epigenomic levels.

Plant sodium/hydrogen (Na+/H+) antiporters (NHXs) are key Na+ transporters, and play vital roles in plant growth, development and abiotic stress responses, in particular salinity stress. Present study was aimed at genome-wide identification, comprehensive in silico characterization and involvement of NHX antiporters in plant development and abiotic stress responses of Indica rice (Oryza sativa subsp. indica). Though there are reports of screening of NHXs from Japonica rice, such reports are lacking from the Indica counterparts. In the current investigation, genome-wide screening of O. sativa Indica subspecies revealed sixteen NHX orthologous, and these were confirmed to be Na+/H+ exchangers. The identified OsNHXs were distributed across nine chromosomes of O. sativa Indica. Probable sites of the OsNHXs were cell membranes or vacuoles, as suggested by their sub-cellular localization. The cis-regulatory elements of OsNHX promoters indicated their involvement in environmental stress responses. OsNHXs were predicted to be targets of 91 miRNA candidates belonging to 10 families. Three-dimensional OsNHX protein structures were also predicted using bioinformatics tools. In order to gain insights into the functional roles of the identified OsNHXs, digital gene expression analysis was carried out and the results revealed that the expression levels of OsNHXs varied amongst the growth and developmental phases and under salinity and drought stress conditions. These results hold significance in identifying potent NHX candidates from Indica rice, having key roles in Na+ transport and in maintaining cellular ionic homeostasis, and can be further explored as potent candidate genes for engineering salinity tolerance in rice and other crop plants.