Abstract: 【Aim】 Ascosphaera apis is a fungal pathogen that infects Apis mellifera ligustica larvae and causes chalkbrood in honeybee colonies. This study aims to investigate the effects of A. apis infection on the expression of genes related to intestinal immunity and detoxification and the contents of proteins, lipids and carbohydrates in the gut of A. m. ligustica larvae, and to analyze the relationship between the immune response and nutrients of A. m. ligustica under A. apis infection. 【Methods】 The A. m. ligustica larvae were raised in the laboratory. Each 3-day-old larva was inoculated with 2×10⁶ spores/mL of A. apis in the treatment group, and that in the control group was fed with the normal food. Then, the gut samples of 6-day-old larvae were collected. The expression levels of genes related to immune, detoxification and development and genes of pathogens in the gut samples were detected by qRT-PCR, and the contents of proteins, lipids, glucose, and glycogen in the gut samples were determined by biochemical methods. 【Results】 After A. apis infection, the expression levels of immune-related genes LOC406144, Apid1, Def1, Def2, LOC406142, PGRP-SA, Pgrp-s2, PGRP-S3, PGRP-lc, GNBP-1, GNBP3, PPOact, LOC552247, domeless, KAT2A and bsk in the larval gut of A. m. ligustica were significantly up-regulated and that of cactus was significantly down-regulated. The expression levels of detoxification-related genes Cat, GSTS3, Cyp4g11, LOC725294, Ampka-r1, LOC411223, LOC409791, AmNOS and Sod2 in the larval gut of A. m. ligustica infected by A. apis were significantly up-regulated and those of CYP6AS14, CPR14, CYP306A1 and LOC100576555 were significantly down-regulated. The expression level of development-related gene usp in the larval gut of A. m. ligustica infected by A. apis was significantly up-regulated and those of VGMC, HEX70b and Vg were significantly down-regulated. The expression levels of pathogen genes BQCV capsid protein and Ascosphaera apis 28S rRNA in the larval gut of A. m. ligustica infected by A. apis were significantly up-regulated. The contents of proteins and lipids in the larval gut of A. m. ligustica infected by A. apis were significantly down-regulated, and those of glucose and glycogen were significantly up-regulated. 【Conclusion】 The A. apis infection influences the expression of genes related to immune, detoxification and development and genes of pathogens in the gut of A. m. ligustica larvae, affecting the immune response and energy stress response and accelerating the loss of proteins and lipids and the energy reservation of glucose and glycogen, and these may result in abnormal physiological activities of A. m. ligustica larvae.

Key words: Apis mellifera ligustica; Ascosphaera apis, immune-related gene, detoxification-related gene, immune response, nutrients