Functional polymorphism of CYCLE underlies the diapause variation in moths
Shirui Zheng, Yaohui Wang, Guiyun Li, Sheng Qin, Zhi Dong, Yang Xu, Xiaomiao Xu, Gangqi Fang, Muwang Li, Shuai Zhan
Abstract
Diapause is a common seasonal adaptive strategy that regulates annual timing in insects. Very few causal loci underlying diapause variation have yet been identified. By leveraging cross-mapping and genome-wide association analysis, we identified the N terminus of the clock protein CYCLE as a major causal effector underlying embryonic diapause differences in the silk moth. We found that the nondiapause phenotype in polyvoltine strains results from a specific deletion that disrupts an alternative isoform of CYCLE. We further demonstrated that different CYCLE isoforms contribute to a functional diversity in modulating circadian rhythms and diapause, which has been preserved in Lepidoptera for at least 110 million years. Our study proposes a model that explains how adaptive phenotypes can evolve rapidly without affecting related essential functions.