Liming Shi, Tingting Liu, Caizhi Zhao, Zhilong Liu, Xin Li, Shun Wang, Feifei Zheng, Hongfang Chen, Miao Zhang, Shasha Yu, Ying Wang
Bacillus thuringiensis subsp. israelensis (Bti) is widely employed in mosquito control due to its highly potent larvicidal activity. However, few studies have investigated the sublethal effects of this biopesticide during field applications. The present study focuses on how a sublethal dose (LC50) of Bti affects the fecundity of surviving Anopheles stephensi, as well as the underlying mechanisms. It was unexpectedly found that larval exposure to sublethal Bti significantly increased laid eggs and total eggs (laid eggs plus eggs retained in the ovaries) in the surviving female adults. Further results showed that Bti-derived DNA was detected in female adults that survived larval exposure to the sublethal LC₅₀ concentration of Bti. Mechanistically, sublethal-dose Bti treatment significantly upregulated the target of rapamycin signaling pathway and vitellogenin expression in adult females, thereby enhancing fecundity. Transcriptome data revealed that autophagy and carotenoid metabolism might be involved in the physiological processes related to mosquito reproduction enhancement by sublethal Bti exposure. This study highlights the potential risks of improper Bti dosage selection in practical applications and also enriches the fundamental research on sublethal effects of biolarvicides. Importantly, our findings provide a novel theoretical reference for the optimization of sustainable mosquito vector control strategies.