<scp> <i>HaJAK2</i> </scp> / <scp> <i>STAT5B</i> </scp> Mediate the Post‐Mating Switch of Reproductive Behaviour in <scp> <i>Helicoverpa armigera</i> </scp> Female

ABSTRACT Mated female moths display behavioural and physiological changes such as oviposition initiation, reduced receptivity and shortened lifespan. The behavioural transition in post‐mating female insects constitutes a critical adaptive strategy for optimising reproductive success, but little is known about the detailed regulatory molecules. The JAK/STAT signalling pathway has been confirmed to play an important role in insect cell growth, immunity and reproductive processes, but its potential role in post‐mating behavioural transformation is still unclear. In this study, we initially identified core components of the JAK/STAT signalling pathway, HaJAK2 and HaSTAT5B , in Helicoverpa armigera through screening of the NCBI database and transcriptomic data. Then phylogenetic analysis and multiple amino acid sequence alignment revealed high homology of HaJAK2 and HaSTAT5B with homologues of Spodoptera litura and Helicoverpa zea , respectively. QRT‐PCR analysis demonstrated tissue‐specific expression patterns of HaJAK2 and HaSTAT5B , showing predominant expression in the spermathecae/parovaria tissue. Furthermore, RNAi‐mediated gene knockdown experiments indicated that suppressing HaJAK2 and HaSTAT5B expression altered post‐mating behaviours, including reduced oviposition, extended longevity and diminished re‐mating propensity. Finally, we revealed that the transcription factor HaGATAa dynamically regulates the expression of HaJAK2 and HaSTAT5B . In conclusion, this study reveals that the GATAa‐JAK/STAT axis governs reproductive state‐dependent behavioural transitions in lepidopteran post‐mating processes, advancing our understanding of insect reproductive strategies and identifying the JAK/STAT cascade as a potential target for novel pest control interventions to disrupt key reproductive behaviours in agricultural pests.