ABSTRACT
Drought is a major abiotic stress that causes greater loss to crops than other abiotic stresses, particularly in tropical and subtropical regions of world. The plant kingdom has withstood the adverse effects of drought by evolving either tolerance or avoidance mechanisms. Both of these invoke a multigenic response to drought stress by comprising of a large number of genes, whose expression is regulated by complex mechanisms. Despite reasonable progress in understanding the role of the transcriptional regulation of genes and the generation of transgenic plants over-expressing transcription factor (TF) genes, limited success has been recorded in drought tolerance. In recent times, micro RNAs (miRNA) have been characterized from a number of plant species under abiotic stress conditions, and have been attributed to the post-transcriptional regulation of gene expression in plants. A growing body of evidence suggests differential expression patterns and an inverse correlation between miRNAs and their target gene expression. Though the altered expression of miRNAs and resultant improvements in tolerance to abiotic stresses are promising, the identification and validation of their targets can provide functional evidence to their utility in such ameliorative genetic engineering. This chapter intends to provide an insight into the possible nature of the miRNA targets and pathways/ networks being modulated by miRNA to influence gene expression in favor of either avoidance or tolerance. Also, this chapter provides a future perspective of the miRNA-based regulation of gene expression for crop improvement.
