The role of plant small RNAs in NB-LRR regulation

Small RNAs constitute a fundamental layer of gene regulation for diverse biological processes in plants, including development, metabolism and stress responses. With the advance of high-throughput sequencing technologies and the rapid accumulation of transcriptomic data, the scope of regulation afforded by small RNAs has expanded to encompass plant innate immune responses. Plants have evolved the capacity to control the infection through intracellular surveillance proteins of the nucleotide binding site-leucine-rich repeat (NB-LRR) family that recognize pathogen-encoded effectors and initiate effector-triggered immunity. Emerging evidence indicates that plants have evolved to use specific microRNAs that target conserved domains of NB-LRR-encoding genes and trigger the production of a phased array of 21-nucleotide secondary small interfering RNAs to amplify the silencing effect. Herein, this review describes recent advances in understanding the roles of small RNAs in NB-LRR regulation that provide new insights into small RNA-mediated arms race between plants and their pathogens and discuss the unresolved questions and the future prospects for research on this topic.