Calreticulin in Cotesia plutellae suppresses immune response of Plutella xylostella (L.)

• We identified calreticulin (Cp-CRT) gene from transcriptome data of the venom gland in C. plutellae.
• Cp-CRT encodes 403 amino acids harboring several conserved structural motifs as found in other calretiulins.
• Recombinant Cp-CRT was successfully expressed and suppressed significant nodule formation when co-injected with E. coli as immune response inducer.

An endoparasitoid wasp, Cotesia plutellae, parasitizes young larvae of the diamondback moth, Plutella xylostella, which is a major pest in cruciferous crops. Successful parasitization requires both maternal and embryonic factors of C. plutellae, such as polydnavirus, ovarian proteins, teratocytes and venom proteins. In this study, we identified calreticulin (Cp-CRT) gene from transcriptome data of the venom gland in C. plutellae which encodes 403 amino acids harboring several structural motifs such as CRT family motif I and II, repetitive sequence (DP(X)3KPEDW), and endoplasmic reticulum-recognizing domain (-HDEL). Phylogenetic analysis showed that the Cp-CRT gene formed a unique cluster with other hymenopteran CRT genes. To examine the physiological function of Cp-CRT, recombinant Cp-CRT, fused with 6X-His at N-terminus, was expressed in Escherichia coli. Recombinant Cp-CRT was successfully expressed and suppressed significant nodule formation when co-injected with E. coli as immune response inducer. These results suggest that the Cp-CRT contributes to suppression of cellular immune response in the host.

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