R-loops: emerging key regulators in plants.

The biological implications of R-loops are increasingly receiving attention in plant biology. Compared with recent progresses in humans, the studies of R-loops in plants are lagging behind. Massive efforts must be invested by the plant community to better harness the possible regulatory functions of R-loops. Pioneering studies indicate that R-loops might act as key regulators of plant growth and development, and stress responses. This review thus timely updates the biological implications of R-loops and proposes a series of future lines of investigations to further decipher R-loop biology in plants. The following three aspects are included: the interplay between R-loops and epigenetic modifications at DNA, RNA, and chromatin levels; their regulatory roles in genome integrity, centromere functions, and DNA replication; and how they likely control plant growth and development as well as stress responses and RNA processing. Altogether, the wealth of information provided here portrays R-loop biology in plants accurately, and makes these new regulators interesting genetic levers in developing plants with new and beneficial agronomical traits.