Study on the functional role and tissue localization of GmolTrypsin in larvae of Grapholita molesta feeding on different host plants

Abstract

Grapholita molesta is an important pest of fruit trees worldwide. Its larvae feed on a wide range of hosts, including fruits, as well as tender shoots, causing significant damage and making effective control challenging. Trypsin is an important digestive enzyme in the midgut of insects, playing a crucial role in digestion, growth, and development. We identified and cloned the trypsin genes, GmolTrypsin1 and GmolTrypsin10, both of which showed the highest expression levels in 4th instar larvae and the midgut. We utilized RNA interference to silence GmolTrypsin1 and GmolTrypsin10 in G. molesta larvae feeding on artificial diets, peaches, pears, plums, apples, and peach shoots. The expression level of the target genes decreased by 64–73 %, and western blot analysis confirmed a significant reduction in protein expression in the treatment group.

Silencing GmolTrypsin1 led to significant changes in the relative activity of trypsin at the larval stage, in pupal weight, and in the emergence rate of G. molesta larvae fed on peach shoots. Silencing GmolTrypsin10 caused significant effects in larvae fed peach, apple, pear, and plum. We clarified the expression sites of GmolTrypsin1 and GmolTrypsin10, and their proteins in the midgut of G. molesta larvae and Sf9 cells. Our study demonstrated the roles of GmolTrypsin1 and GmolTrypsin10 in regulating G molesta larval responses to different host plants and clarified their localization in the larval midgut, providing an important theoretical basis for the development of pest control strategies targeting midgut digestive enzymes.