The CYP303A1 is essential in embryonic development of Nilaparvata lugens Stål (Hemiptera: delphacidae)

The <i>N. lugens</i> is a highly fecund rice pest that causes severe damage to rice production in Asia. Cytochrome P450 monooxygenases (P450s) play essential roles in insect development, metabolism, and reproduction. In a previous study, we identified and functionally characterized CYP303A1, a member of the CYP2 family, in <i>N. lugens</i> molting and metamorphosis process. However, it is unclear the function of CYP303A1 in <i>N. lugens</i> fecundity. In this study, the expression profiling showed that <i>CYP303A1</i> is highly expressed in legs and adult fat bodies, with moderate expression in the ovaries. Silencing of <i>CYP303A1</i> in females had no significant effects on <i>Vg</i> (Vitellogenin) and <i>VgR</i> (Vitellogenin receptor) transcript levels, ovarian morphology, oocyte number, oviposition period, or female lifespan, indicating that CYP303A1 is not involved in vitellogenesis or ovarian development. However, knockdown of <i>CYP303A1</i> significantly prolonged the embryonic period and reduced egg hatchability. Morphological observations revealed that silencing <i>CYP303A1</i> led to abnormal embryonic development, including delayed eyespot formation and dispersed yolk granules. Furthermore, the expression levels of several egg hatchability-related genes, including <i>Cpr52</i>, <i>TwdIE3</i>, <i>HNF4</i>, and <i>Let1</i>, were significantly altered following <i>CYP303A1</i> silencing. These findings suggest that CYP303A1 is essential for successful embryogenesis in <i>N. lugens</i>, likely by regulating the expression of hatching-related genes. This work expands our understanding of the non-Halloween CYP genes in insect reproduction and provides a potential molecular target for disrupting <i>N. lugens</i> population development.