Role of microRNAs in Plant–Fungus Interactions

Abstract

MicroRNAs (miRNAs) are small noncoding RNAs involved in post-transcriptional regulation of gene expression in eukaryotes. Given the rapid advancement of sequencing techniques, there has been a dramatic increase in the number of described miRNAs in plants. miRNAs act as master regulators of diverse plant developmental processes and adaptation to environmental stress. Evidence has also emerged on miRNAs involved in antifungal and antibacterial resistance by regulating ETI and PTI responses. Small RNAs, including miRNAs, also mediate cross-kingdom regulation of gene expression in host/pathogen interactions where specific host-derived miRNAs can be transmitted to the pathogen to downregulate genes essential for pathogen virulence. Thus, plants might have adapted cross-kingdom RNA interference mechanisms as part of their battery of immune responses used to arrest pathogen infection. However, although a large number of miRNAs are known to be regulated during pathogen infection, the biological role of the majority of these pathogen-regulated miRNAs has not yet been determined. In this review, we focus on miRNAs for which functional evidence exists on their involvement in the plant response to pathogen infection, mainly fungal pathogens. Elucidation of the function of miRNAs in plant immunity holds great potential for developing novel strategies to improve disease resistance in plants.