Regulatory Role of Micro-RNAs in Plants Under Challenging Environmental Conditions with Special Focus on Drought and Salinity

Micro-RNAs (miRNAs) are small, 20–24 nucleotide long, non-coding RNAs that can coordinate vital regulatory functions in key metabolic processes in plants. Their primary mode of action is based on homology-based binding with the desired gene(s), followed by a site-specific cleavage or translational silencing of the target transcripts. They play major roles in the growth and development of a plant and also aid it in adapting to different climates, thereby preventing yield losses. With the advancement of the genome editing technologies, miRNAs are being employed to control the defense response genes and impart tolerance to the crop plants against various abiotic stresses, such as drought, salinity, heat, cold, flooding, and heavy metal toxicity. Together with effector genes, these form regulatory circuits and modulate the outcome of the plant metabolic pathways, which can be localized to a particular tissue or can affect the entire plant. In this chapter, we have summarized and discussed the recent works that define the regulatory roles of miRNAs in plants under different challenging environmental conditions, with special focus on drought and salt stress. By comprehensive understanding of the regulatory roles of miRNAs may be utilized and engineered for the crop improvement programs, which can cause a major impact on increasing food production rate and food quality for the benefits to the increasing world population day by day.