MicroRNAs: A potential resource and tool in enhancing plant tolerance to drought

Abstract

Drought is a predominant factor limiting plant productivity. To cope with drought stress, plants use a range of defence systems involving reprogramming of gene expression. As an important gene regulator, microRNAs (miRNAs), a novel class of small noncoding RNA molecules, play a key role in the reprogramming. MiRNAs regulate the expression of drought-responsive genes both positively and negatively mainly at the posttranscriptional level by either cleaving (mRNA) targets or repressing the translation of mRNA targets. Most targets of miRNAs are transcription factors (TFs), another important type of gene regulator. Considering their tremendous regulatory potential and their often drought-specific expression patterns, miRNAs might offer potential for genetic modification of crop plants to increase drought tolerance. Compared to other types of transgenes, miRNAs offer easy manipulation, no protein product, and target specificity. In this chapter, we review the knowledge on biogenesis and functional mechanisms of miRNAs, drought-responsive miRNAs, and miRNA-regulated drought-responsive genes, and explore strategies for the utilisation of miRNAs in the improvement of crop tolerance to drought.