The Fat/Hippo pathway drives photoperiod-induced wing length polyphenism

Identifying the genetic mechanisms that translate information from the environment into developmental programs to control size, shape and color are important for gaining insights into adaptation to changing environments. Insect polyphenisms provide good models to study such mechanisms because environmental factors are the main source of trait variation. Here we studied the genetic mechanism that controls photoperiod-induced wing length polyphenism in the water strider Gerris buenoi . By sequencing RNA sampled from wing buds across developmental stages under different photoperiodic conditions known to trigger alternative wing developmental trajectories, we found that differences in transcriptional activity arose primarily in the late 5 ^th instar stage. Among the differentially expressed genes, the Fat/Hippo and ecdysone signaling pathways, both putative growth regulatory mechanisms showed significant enrichment. We used RNA interference against the differentially expressed genes Fat, Dachsous and Yorkie to assess whether they play a causative role in photoperiod induced wing length variation in Gerris buenoi . Our results show that the conserved Fat/Hippo pathway is a key regulatory network involved in the control of wing polyphenism in this species. This study provides an important basis for future comparative studies on the evolution of wing polyphenism and significantly deepens our understanding of the genetic regulation of insect polyphenisms.