Abstract: 【Aim】The aim of this study is to explore the function of the ferritin1HCH (Fer1) gene HvFer1 in the 28-spotted ladybeetle, Henosepilachna vigintioctopunctata, and to provide a theoretical basis for the biological control of H. vigintioctopunctata. 【Methods】The amino acid sequence of HvFer1 was subjected to blastp analysis followed by multiple alignment with Fer1 sequences from different species. The expression levels of HvFer1 in different developmental stages (egg, 1st-4th instar larvae, pupa, and female and male adults) and different tissues (head, midgut, fat body, cuticle and Malpighian tubules) of the 4th instar larvae of H. vigintioctopunctata were detected by RT-qPCR. HvFer1 was silenced by injecting 200 ng/individual of dsHvFer1 into the 3rd instar larvae of H. vigintioctopunctata. Then the larval phenotype, survival rate and duration from the 4th instar larva to pupa, as well as the expression level of dual oxidase (Duox) gene HvDuox, the level of reactive oxygen species (ROS), the content of malondialdehyde (MDA), and bacterial diversity in the midgut were observed and determined. 【Results】The coleopteran Fer1 sequences clustered into one clade, and HvFer1 was the most closely related to Fer1s of Harmonia axyridis and Coccinella septempunctata. The expression level of HvFer1 was the highest in male adults and the lowest in the 4th instar larvae of H. vigintioctopunctata. The expression level of HvFer1 in the midgut of the 4th instar larvae of H. vigintioctopunctata was significantly higher than those in the other tissues. Compared with the control group (dsGFP injection), injection of 200 ng/individual of dsHvFer1 into the 3rd instar larvae of H. vigintioctopunctata significantly prolonged the duration from the 4th instar larva to pupa, and prevented the formation of some spines and spots in pupae. The elyta of the emerged adults of H. vigintioctopunctata were abnormally developed after dsHvFer1 injection, with spots fused or deficient. The expression level of HvFer1 in the 3rd instar larvae of H. vigintioctopunctata on the 2nd day post injection of dsHvFer1 showed no significant difference from that in the control group, but the expression level of HvFer1 on the 4th day post injection of dsHvFer1 was significantly lower than that in the control group. Compared with the control group, HvFer1 silencing caused severe oxidative stress in H. vigintioctopunctata larvae, significantly up-regulated the expression level of HvDuox, ROS level and MDA content in the larval midgut, changed the structural composition of midgut bacteria, reduced the relative abundance of Enterobacter and Chryseobacterium, and also increased the relative abundance of Serratia, Pseudomonas, Acinetobacter and other intestinal bacteria.【Conclusion】 HvFer1 plays a crucial role in regulating the larval development, adult phenotype, and maintaining the larval gut immunity and microbial homeostasis of H. vigintioctopunctata. HvFer1 is expected to be a candidate target gene for controlling H. vigintioctopunctata based on RNAi technology.

Key words: Henosepilachna vigintioctopunctata, ferritins, gene function, RNA interference, oxidative stress, reactive oxygen species, microbial homeostasis