piR-ame-1128833 as a Pivotal Regulator for the Survival and Immune Response of Honeybee Larvae to Fungal Invasion

Piwi-interacting RNAs, a class of small noncoding RNAs, play key roles in immunity and developmental regulation. <i>Ascosphaera apis</i>, a lethal fungal pathogen, causes chalkbrood disease in honeybee (<i>Apis mellifera</i>) larvae. Herein, worker larvae were inoculated with <i>A. apis</i> spores, and gut paraffin sections were examined histologically. The activities of four antioxidant enzymes─superoxide dismutase, catalase, glutathione <i>S</i>-transferase, polyphenol oxidase─were substantially reduced in the infected larvae. Functional analyses of piR-ame-1128833 revealed that its overexpression or knockdown altered the expression of key immune genes (<i>Imd</i>, <i>abaecin</i>, and <i>Cact</i>), influenced larval survival, and affected the incidence of chalkbrood disease. Moreover, three fungal-virulence-related genes (<i>Mat</i>1-2-1, <i>Ste</i>11-like, and <i>Htf</i>) were markedly altered by piR-ame-1128833 overexpression or knockdown. Collectively, these findings highlight the regulatory role of piR-ame-1128833 in modulating the immune response of <i>A. mellifera</i> larvae against <i>A. apis</i> infection, providing novel insights into honeybee-pathogen interactions and identifying a potential molecular target for chalkbrood diagnosis and control.