R-loop:The new genome regulatory element in plants

An R-loop is a three-stranded chromatin structure that consists of a displaced single strand of DNA and an RNA:DNA hybrid duplex,which was thought to be a rare by-product of transcription.However,recent genome-wide data have shown that R-loops are widespread and pervasive in a variety of genomes,and a growing body of experimental evidence indicates that R-loops have both beneficial and harmful effects on an organism.To maximize benefit and avoid harm,organisms have evolved several means by which they tightly regulate R-loop levels.Here,we summarize our current understanding of the biogenesis and effects of R-loops,the mechanisms that regulate them,and methods of R-loop profiling,reviewing recent research advances on R-loops in plants.Furthermore,we provide perspectives on future research directions for R-loop biology in plants,which might lead to a more comprehensive understanding of R-loop functions in plant genome regulation and contribute to future agricultural improvements.