Host population related variations in circadian clock gene sequences and expression patterns in Chilo suppressalis

ABSTRACT

The rice stem borer, Chilo suppressalis Walker, is one of the most important global agricultural pests. C. suppressalis has distinct rice and water-oat host populations. Asynchrony in sexual activity is thought to be the main factor maintaining reproductive segregation between these populations, particularly the obvious difference in the circadian rhythm of female calling activity between populations. However, the mechanism responsible for this difference in the timing of female calling is poorly understood. The circadian clock is an essential regulator of daily behavioral rhythms in insects, including female calling. We investigated the variation in circadian clock genes of the rice and water-oat populations of C. suppressalis. We did this by comparing deduced amino acid sequences and the expression patterns of seven circadian clock genes (clock, cycle, period, timeless, timeout, cryptochrome1, and cryptochrome2) between females from each population. We found that the two populations had different variants of the timeout and cryptochrome1 genes and differed in the expression of period, timeless and timeout. This suggests that population-related variation in the circadian clock genes period, timeless, timeout and cryptochrome1 could be responsible for the different circadian rhythms of female calling in these host population of C. suppressalis. These results provide new insights into the molecular mechanisms underlying asynchronous sexual activity in insect populations and suggest new topics for future research on the origins and maintenance of population differentiation in insects.

KEYWORDS:

• Chilo suppressalis
• host race
• sexual activity
• circadian clock gene

Acknowledgments

We sincerely thank the support of Wei-Li Quan, Rong Chen, Yuan Zhou and Zhong Tian for insect collecting and rearing.

Declaration of Interest Statement

The authors declare no competing interests.

Additional information

Funding

This study was funded by grant from the Hubei Provincial Natural Science Foundation of China (Grant number 2016CFA068).