Transcriptome analysis of Diplolepis rosae: revealing overexpression of genes potentially associated with insect immune response and gall formation at early larval stages

Insect parasites can provoke drastic changes in host plant physiology by affecting cell differentiation pathways and various metabolic processes. An intriguing example of such interaction is a gall, a novel outgrowing plant organ, induced by another organism for its own benefit. Cynipidae is a family of gall-inducing hymenopterans that induce galls with a complex anatomical structure. Gall formation involves three stages: initiation, growth, and maturation. Until today, the mechanism of gall initiation remains unknown. In this study, we aimed to reveal candidate genes involved in gall induction in Diplolepis rosae, a gall wasp inducing bedeguars in wild roses. We performed differential expression analysis of the gall wasp larva transcriptome. We observed the overexpression of genes encoding plant cell wall degrading enzymes. These enzymes may contribute to the formation of a chamber for a developing larva by lysing plant tissues. We also demonstrated the overexpression of genes encoding podocan, vasorin-like protein, toll-like receptor 7, tetraspanin, lipase, peroxidase, phospholipase A2, and venom acid phosphatase. These genes may be involved in insect development and the immune response against parasitoids, host plant microbiome, and host plant defense systems. Additionally, we performed a test for selection to detect D. rosae genes under positive selection. However, we detected only one gene encoding a transposable element. This can be explained by the mostly asexual reproductive mode of this species. Thus, our study contributes to understanding the processes occurring in cynipid wasps during gall formation and creates opportunities for further investigations of other candidate genes.