Characterization and Functional Analysis of trehalase Related to Chitin Metabolism in Glyphodes pyloalis Walker (Lepidoptera: Pyralidae)

Simple SummarySericulture has always been threatened byGlyphodes pyloalisWalker (G. pyloalis). Trehalase is an essential enzyme in chitin metabolism and energy supply. In this study, two trehalase genes inG. pyloalis(GpTre1andGpTre2) were identified and functionally analyzed. Knockdown of the two genes led to the significant downregulation of chitin metabolism pathway-related genes, the difficulty in molting of larvae, and the deformation of adult wings. Moreover, the trehalase inhibitor, Validamycin A, treatment increasedGpTre1andGpTre2expression and affected the expressions of chitin metabolism pathway-related genes. The inhibitor also caused a significantly increased cumulative mortality of larvae. The results suggested thatGpTre1andGpTre2played a vital role onG. pyloalisdevelopment, which could be useful for providing information for insect pest control in the future.AbstractGlyphodes pyloalisWalker (G. pyloalis) is a serious pest on mulberry. Due to the increasing pesticide resistance, the development of new and effective environmental methods to controlG. pyloalisis needed. Trehalase is an essential enzyme in trehalose hydrolysis and energy supply, and it has been considered a promising target for insect pest control. However, the specific function oftrehalaseinG. pyloalishas not been reported. In this study, two trehalase genes (GpTre1andGpTre2) were identified from our previous transcriptome database. The functions of thetrehalasein chitin metabolism were studied by injecting larvae with dsRNAs and trehalase inhibitor, Validamycin A. The open reading frames (ORFs) of GpTre1 and GpTre2 were 1,704 bp and 1,869 bp, which encoded 567 and 622 amino acid residues, respectively. Both ofGpTre1andGpTre2were mainly expressed in the head and midgut. The highest expression levels of them were in 5th instar during different development stages. Moreover, knockdown both ofGpTre1andGpTre2by the dsRNAs led to significantly decreased expression of chitin metabolism pathway-related genes, includingGpCHSA,GpCDA1,GpCDA2,GpCHT3a,GpCHT7,GpCHSB,GpCHT-h,GpCHT3b,GpPAGM,andGpUAP, and abnormal phenotypes. Furthermore, the trehalase inhibitor, Validamycin A, treatment increased the expressions ofGpTre1andGpTre2, increased content of trehalose, and decreased the levels of glycogen and glucose. Additionally, the inhibitor caused a significantly increased cumulative mortality ofG. pyloalislarvae on the 2nd (16%) to 6th (41.3%) day, and decreased the rate of cumulative pupation (72.3%) compared with the control group (95.6%). After the activities of trehalase were suppressed, the expressions of 6 integument chitin metabolism-related genes decreased significantly at 24 h and increased at 48 h. The expressions ofGpCHSBandGpCHT-h, involved in chitin metabolism pathway of peritrophic membrane in the midgut, increased at 24 h and 48 h, and there were no changes toGpCHT3bandGpPAGM. These results reveal thatGpTre1andGpTre2play an essential role in the growth ofG. pyloalisby affecting chitin metabolism, and this provides useful information for insect pest control in the future.Keywords:Glyphodes pyloalisWalker;trehalase;chitin metabolism;Validamycin A;RNA interference;pest control