Abstract: 【Aim】 To explore the molecular characteristics, expression patterns and biological function of the E3 ubiquitin ligase gene NlHECTD2 of Nilaparvata lugens.【Methods】 Based on the transcriptome data of N. lugens, the full-length cDNA sequence of NlHECTD2 was cloned by PCR and bioinformatically analyzed. qRT-PCR was used to detect the expression levels of NlHECTD2 in the egg, 1st-5th instar nymphs, female adult newly emerged within 24 h and 1-5-day-old female adults, and the head, throax, abdomen, gut and ovary of the 3-day-old female adult of N. lugens. A single newly emerged female adult of N. lugens was injected with 0.05 μL dsNlHECTD2 (5 000 ng/μL) and the expression level of NlHECTD2 was detected by qRT-PCR at 24, 48, and 72 h after RNAi, and the number of yeast-like symbionts (YLSs) in the hemolymph, survival rate of the female adult of N. lugens, number of eggs laid per female and egg hatching rate were also detected.【Results】 The full-length cDNA sequence of NlHECTD2 (GenBank accession number: XM_039427060.1) was successfully cloned from N. lugens. The open reading frame (ORF) of NlHECTD2 is 2 850 bp in length and encodes 950 amino acids. NlHECTD2 has no signal peptide and contains a C-terminal catalytic domain with a subclass ubiquitin ligase (E3). Phylogenetic analysis indicated that NlHECTD2 was clustered together with other hemipteran HECTD2s, and had the highest homology with HECTD2 of Bemisia tabaci. The qRT-PCR results showed that NlHECTD2 had obvious spatiotemporal expression specificity, with the highest expression level in the abdomen of the 3-day-old female adult of N. lugens. The RNAi results showed that compared with the control (injected with dsGFP), injection of dsNlHECTD2 significantly inhibited the expression level of NlHECTD2 and extremely significantly decreased the number of YLSs in the hemolymph of N. lugens, which led to an extremely significant decrease in the survival rate of female adult, number of eggs laid per female and egg hatching rate of N. lugens.【Conclusion】 NlHECTD2 is closely related to the process of YLS release to hemolymph in N. lugens, plays an important role in the growth, development and reproduction of N. lugens, and can be used as a potential target for the control of N. lugens.

Key words: Nilaparvata lugens; NlHECTD2, yeast-like symbiont, RNA interference, gene function