Excess trehalose and glucose affects chitin metabolism in brown planthopper (Nilaparvata lugens)

Abstract Trehalose is a non-reducing disaccharide that is hydrolyzed by trehalase to yield two glucose molecules. Trehalase is the first enzyme involved in the chitin biosynthesis pathway, and it plays a pivotal role in insect growth and molting. In this study, Nilaparvata lugens , an economically important rice pest in Southeast Asia, was injected with trehalose or glucose to investigate their effects on chitin metabolism. Excess trehalose and glucose significantly increased the rate of deformity (molting and/or wing deformities) and mortality in N . lugens . Trehalose, glycogen, and glucose contents were also significantly decreased in N . lugens treated with trehalose or glucose. Chitin content and the expression of NlHK , NlUAP , NlG6PI1 , NlGFAT , NlGNPNA , NlPGM1 , NlPGM2 , NlCHS1 , NlCHS1a , NlCHS1b , NlCht3 , NlCht4 , NlCht6 , and NlCht7 were significantly decreased, whereas the expression of NlCht2 , NlIDGF , and NlENGase was significantly increased in treated insects. Furthermore, a significant increase in the expression of NlTRE1-1 , NlTRE2 , and NlTPS1 and a decrease, in the expression of NlTPS2 were observed. Results of this study suggested that excess trehalose and glucose could affect chitin metabolism by regulating the expression of pivotal genes to decrease the chitin content, resulting in the inability of N . lugens to complete its molting process.