Transcriptomic analysis of cold stress-response in Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae)

Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae) is a solitary ectoparasitoid that parasitizes several stored product beetles. Implementing an effective cold storage program can extend the shelf life of parasitoids for large scale applications in biological control. To explore the low temperature adaptation mechanisms of A. calandrae, the survival, longevity, parasitism rate, fecundity, and transcriptome of cold-treated A. calandrae adults were investigated. Storing A. calandrae adult wasps at 15 °C and 10 °C for 1 week had no significant difference in terms of adult longevity, parasitism rate, and progeny compared with the control. By analysing the gene expression patterns and comparing the whole transcriptome of cold-treated A. calandrae adults (adults after cold storage at 15, 10, or 5 °C for 1 week, referred to as T2, T3, and T4, respectively, and adults without experiencing cold storage referred to as T1), a total of 1376, 9799, and 7745 differentially expressed genes (DEGs) were respectively identified (T1 vs T2, T1 vs T3, T1 vs T4). A total of 196 commonly up-regulated genes and 100 commonly down-regulated genes in T1 vs T2, T1 vs T3, and T1 vs T4 treatments were identified. A total of 6 modules composed of differentially co-expressed genes were identified by weighted gene co-expression network analysis (WGCNA). The Mebrown module was extremely associated with the T4 sample. Mebrown module of genes was found to be highly correlated with the metabolic process (217 genes), cell part (148 genes), and catalytic activity (225 genes). Four transcription factor genes, LOC111691805, LOC126386779, LOC108733382, and LOC108906572 were presented in Mebrown module as hub genes. The changes in gene expression indicated that A. calandrae can significantly upregulate the expression levels of abiotic related genes, such as the heat shock protein (Hsp 90) gene, cytochrome P450, and calnexin gene, etc., to cope with cold stress. The current results provide the molecular mechanisms and identify the key genes that may explain the adaptation of A. calandrae to cold stress.