Transcriptome analysis of Grapholitha molesta (Busk) (Lepidoptera: Tortricidae) larvae in response to entomopathogenic fungi Beauveria bassiana

Beauveria bassiana is an entomopathogenic fungus with wide host range and is an important biocontrol agent against the oriental fruit moth Grapholitha molesta (Busck) (Lepidoptera: Tortricidae), a key pest of tree fruits worldwide. However, the molecular mechanisms involved in the interactions between G. molesta and B. bassiana is poorly understood. Herein, high throughput sequencing technology, the Illumina RNA-seq platform was used to analyze the transcriptome of G. molesta larvae induced by B. bassiana. De novo assembly generated 48,980 unigenes and the mean length is 1,226 nt. All of the unigenes were searched against Nt, Nr, GO, KOG databases, and 23,825 (46.64%) unigenes have been annotated in at least one database. Pairwise comparisons resulted in 1,755 differentially expressed genes (DEGs), with 965 up-regulated and 790 down-regulated. We further explored differentially expressed genes that are related to the infection of B. bassiana to G. molesta, especially the up-regulated ones. The potential immune-related genes were identified based on sequence similarity to homologs known to participate in immune response, and their expression was further verified by qRT-PCR. This is the first study on the molecular mechanism of entomopathogenic fungi -G. molesta interactions. The obtained data also provide insights for better understanding the molecular mechanisms of innate immune responses in G. molesta larvae against B. bassiana.