R-loop modulates odor-guided behavior in migratory locusts.

In neurodegenerative disorders, excessive R-loops affect DNA replication, transcription and genome stability. Olfaction impairment is an early indicator of these diseases. However, the function of R-loops in olfactory modulation is less well known. Migratory locusts show olfactory response to locust and plant odorants. Therefore, we chose this insect as a model to study the functions of R-loops in modulating olfaction in the central nervous system. The R-loop exists in the antenna and brain of this insect, and RNase H1 (RNH1), an enzyme that resolves the R-loop structure, is also expressed in these 2 tissues. Immunofluorescence analysis identifies the existence of R-loops in the brain, especially in mushroom bodies and antennal lobes, and RNH1 is also expressed in these 2 brain regions. RNH1 RNA interference (RNAi) knockdown does not affect the locomotion and body color of this insect, but results in the loss of olfactory responses to their own volatiles and plant odorants. Moreover, RNH1 deficiency results in increased R-loop levels in the protocerebrum and antennal lobes of the brain. RNH1 RNAi knockdown results in DNA damage and decreases nascent RNA synthesis in locust brains. This study reports that the increase in R-loop levels resulting from RNH1 knockdown may induce the loss of olfactory response of this insect to conspecific and plant odorants. This study is the first to show that excessive R-loops and RNH1 in the brain are involved in olfactory behavioral regulation. The identification of RNH1-mediated R-loop resolution will provide new insights into the functions of R-loops in modulating olfaction.