RNA Sequencing Reveals the Potential Adaptation Mechanism to Different Hosts of Grapholita molesta

SIMPLE SUMMARY: The oriental fruit moth Grapholita molesta is an important worldwide fruit tree pest. Its hosts mainly include peach, pear, apple, plum and other Rosaceae fruit trees. In order to explore the mechanism of host adaptation, it is necessary to comprehensively study the effects of feeding and the differences in transcriptional levels of G. molesta. In this study, the growth and development parameters, protease activities, midgut transcriptome analysis and key gene validation of G. molesta fed on five hosts and artificial diet were determined. This study indicated that the significant differences in the growth and development parameters and protease activities, transcriptome of KEGG enrichment and WGCNA analysis of G. molesta fed on different hosts. The transcriptional level of the trypsin gene was consistent with that of qRT-PCR. The trypsin gene played an important role in feeding different hosts of G. molesta. We revealed the adaptive mechanism to different hosts of G. molesta in various aspects and laid a solid foundation for further exploring the molecular mechanism of host adaptation. ABSTRACT: Grapholita molesta is an important fruit tree worldwide pest which feeds on hosts extensively and does serious harm. In this paper, the growth and development parameters and protease activities of G. molesta fed on different hosts were compared. Using Illumina RNA sequencing technology, 18 midgut samples from five different hosts (apple, pear, plum, peach and peach shoots) and artificial diet were sequenced and compared with the reference genome, resulting in 15269 genes and 2785 predicted new genes. From 15 comparative combinations, DEGs were found from 286 to 4187 in each group, with up-regulated genes from 107 to 2395 and down-regulated genes from 83 to 2665. KEGG pathway analysis showed that DEGs were associated with amino acid metabolism, starch and sucrose metabolism, carbohydrate metabolism, and hydrolase activity. A total of 31 co-expression gene modules of different hosts were identified by WGCNA. qRT-PCR showed that the expression pattern of the trypsin gene was consistent with RNA sequencing. In this study, growth and development parameters, protease activity, DEGs, enrichment analysis and qRT-PCR were combined to reveal the adaptation process to different hosts of G. molesta in many aspects. The results of this study provide a basis for further exploration of the molecular mechanism of host adaptation of G. molesta.