Abstract
Trehalose-6-phosphate synthase (TPS) and trehalase (TRE) directly regulate trehalose metabolism and indirectly regulate chitin metabolism in insects. Real-time quantitative PCR (RT-qPCR) and RNA interference (RNAi) were used to detect the expressions and functions of the ApTPS and ApTRE genes. Abnormal phenotypes were found after RNAi of ApTRE in the Acyrthosiphon pisum. The molting deformities were observed in two color morphs, while wing deformities were only observed in the red morphs. The RNAi of ApTPS significantly down-regulated the expression of chitin metabolism-related genes, UDP-N-acetyglucosamine pyrophosphorylase (ApUAP), chitin synthase 2 (Apchs-2), Chitinase 2, 5 (ApCht2, 5), endo-beta-N-acetylglucosaminidase (ApENGase) and chitin deacetylase (ApCDA) genes at 24 h and 48 h; The RNAi of ApTRE significantly down-regulated the expression of ApUAP, ApCht1, 2, 8 and ApCDA at 24 h and 48 h, and up-regulated the expression of glucose-6-phosphate isomerase (ApGPI) and Knickkopf protein (ApKNK) genes at 48 h. The RNAi of ApTRE and ApTPS not only altered the expression of chitin metabolism-related genes but also decreased the content of chitin. These results demonstrated that ApTPS and ApTRE can regulate the chitin metabolism, deepen our understanding of the biological functions, and provide a foundation for better understanding the molecular mechanism of insect metamorphosis.
Highlights
Chitin is a polymer of N-acety1-β-d-glucosamine and a major component of the insect cuticle
We measured the activities of soluble trehalase (ApTRE1) and membrane-bound trehalase (ApTRE2) of A. pisum in each dsRNA-injected treatment group and found that the activities of ApTRE1 and ApTRE2 reduced in the dsTRE group compared with control and dsGFP groups (Fig. 2A,B)
The RNA interference (RNAi) of ApTRE resulted in two abnormal phenotypes in the red morphs (Fig. 3A,C), but only one abnormal phenotype was observed in the green morphs when the molting deformities were compared with healthy aphids (Fig. 3A, I-0 and II-0)
Summary
Chitin is a polymer of N-acety1-β-d-glucosamine and a major component of the insect cuticle. Trehalose is a non-reducing disaccharide in insect hemolymph, which has many functions, such as facilitating carbohydrates absorption and acting as an energy source It is the major substrate of chitin biosynthesis and involves in a partial feedback mechanism to regulate feeding behavior and nutrient intake[5,7,9,10]. RNAi of TPS decreased trehalose content and subsequent survival rate, produced three abnormal phenotypes (molting deformities, wing deformities, and molting and wing deformities) and changed the gene expression related to the chitin metabolism in Nilaparvata lugens[12,23], Leptinotarsa decemlineata[14], Tribolium castaneum[25] and Bactrocera minax[26].
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