Structure and expression of a cysteine proteinase gene from Spodoptera litura and its response to biocontrol fungus Nomuraea rileyi

Abstract

Cysteine proteinases (Cyps) play vital roles in many biological processes, including physiological and pathological reactions. In the present study, we cloned a full cDNA of SlCyp, encoding a 344-amino-acid protein from Spodoptera litura. The putative amino acid sequence shared >75% identity with Cyps from other insects. A phylogenetic analysis revealed that SlCyp is closely related to other known lepidopteran Cyps. Real-time PCR and Western blotting analyses showed that SlCyp is induced by Nomuraea rileyi infection in all the tissues tested. The strongest SlCyp mRNA and protein expression was found in haemocytes, followed by the fat bodies, of unchallenged and N. rileyi-challenged S. litura. A time-course analysis showed that SlCyp mRNA and protein expression levels were upregulated in the haemocytes and fat bodies by N. rileyi infection. Upon N. rileyi infection, the proteolytic activities of SlCyp were also significantly higher in the haemolymph than in normal or phosphate-buffered-saline-challenged controls. These results suggest that SlCyp plays an important role in the innate immunity of S. litura in response to N. rileyi. SlCyp mRNA and protein expression and activities were also elevated during sixth-instar moulting and metamorphosis. Knocking down SlCyp transcripts with double-stranded RNA interference caused prepupal, pupal, and adult phenotypic changes, and SlCyp-silenced mutant larvae displayed a significantly lower survival rate after N. rileyi infection. These facts suggest that SlCyp plays a significant role in resisting N. rileyi infection and an essential role in larval development. Our data should facilitate the development of techniques for S. litura control.

Molecular Identification of Cysteine and Trypsin Protease, Effect of Different Hosts on Protease Expression, and Rnai Mediated Silencing of Cysteine Protease Gene in the Sunn Pest

“…Also, in this experiment a significant higher number of abnormality was observed during ecdysis in treated bugs than in the control insects suggesting the involvement of this protease on the insect ecdysis. The involvement of cathepsin‐L in different insect molting has been demonstrated (Hashmi et al., ; Liu et al., ; Zhang et al., ; Chen et al., ; Sapountzis et al., ). As our results, successful RNAi of cathepsin‐L in the pea aphid, A. pisum , was reported by Sapountzis et al.…”

“…Also Chen et al. () indicated that in Spodoptera litura knockdown of cysteine transcripts with dsRNA caused prepupal, pupal, and adult phenotypic changes.…”

“…They observed cathepsin-L knockdown caused alteration of aphid body shape and induced high mortality. Also Chen et al (2014) indicated that in Spodoptera litura knockdown of cysteine transcripts with dsRNA caused prepupal, pupal, and adult phenotypic changes. To conclude, we have for the first time identified two different genes encoding cysteine protease, and trypsin in the Sunn pest and analyzed their expression in addition to gluten hydrolase gene in different tissues on the Sunn pest reared on various hosts.…”