Orchestration of MicroRNAs and Transcription Factors in the Regulation of Plant Abiotic Stress Response

Plants have to tackle daily vagaries of the environment like temperature extremes, drought, excess salt, etc. Together with nutritional imbalances present in the soil, these abiotic stresses are major obstacles in achieving sustainable food production. To mitigate the effects of harsh environmental conditions, an array of regulatory pathways has evolved in plants to coordinate gene expression and cellular signaling to maintain cellular homeostasis. This dynamic reprogramming of gene expression is majorly governed by two trans-regulators: the transcription factors (TFs) and microRNAs (miRNAs). While TFs regulate transcription by binding to the cis-regulatory elements in the promoters of various genes, the miRNAs regulate gene expression by silencing their target genes through mRNA cleavage, translational repression, or DNA methylation. Recent studies have elucidated the intricate stress responsive regulatory circuits involving TFs and miRNAs as focal nodes. Several TF:miRNA modules have been shown to be active under various environmental stress conditions like HSFA1b/A7b:miR398 (heat stress); SPL7:miR398 and HY5-SPL7:miR408 (copper starvation); PHR1:miR399 (phosphate starvation); and SLIM1:miR395 (sulfate deficiency). Since many of the miRNA targets are TFs themselves, several of these modules work as critical sub-networks in abiotic stress response including the miR156:SPL, miR159:MYB, miR169:NF-YA, and miR166:HD-ZIP. This control of plant gene expression at both transcriptional and post-transcriptional levels regulated by TFs and miRNAs, respectively, leads to the establishment of complex regulatory networks which are involved in abiotic stress response in plants. In this chapter, we have reviewed and discussed the detailed information available on the roles of TF:miRNA:target modules in different abiotic stress responses in various plant species including model and crop plants. This information will aid in understanding the mechanisms of action and interactions between these regulators in plant growth and development under normal as well as environmental stress conditions and pave the path to engineer more resilient plants in the future.