Identification and characterization of defensin genes from the endoparasitoid wasp Cotesia vestalis (Hymenoptera: Braconidae) |
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Authors: | Zhi-Zhi Wang Min Shi Wei Zhao Quan-Le Bian Gong-Yin Ye Xue-Xin Chen |
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Institution: | 1. Ministry of Agriculture Key Lab of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China;2. Chinese Associations of Agricultural Science Societies, Beijing 100125, China |
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Abstract: | Defensins are members of a large and diverse family of antimicrobial peptides (AMPs) containing three or four intramolecular disulfide bonds. They are widely distributed from vertebrates to invertebrates, and serve as critical defense molecules protecting the host from the invasion of pathogens or protozoan parasites. Cotesia vestalis is a small endoparasitoid wasp that lays eggs in larvae of Plutella xylostella, a cosmopolitan pest of cruciferous crops. We identified and characterized three full-length cDNAs encoding putative defensin-like peptides from C. vestalis, named CvDef1, CvDef2 and CvDef3. Phylogenetic analyses of these sequences showed that they are present in two clades, CITDs and PITDs, indicating a diversity of defensins in C. vestalis. We analyzed their expression patterns in larvae, pupae and adults by semi-quantitative RT-PCR. The results showed that CvDef1 mRNA was expressed from the end stage of the second instar larva, CvDef3 mRNA from the early stage of the second instar larva, and CvDef2 mRNA was expressed in all developmental stages of C. vestalis. Furthermore, CvDef1 showed antimicrobial activity against gram-positive and gram-negative bacteria. Growth kinetics of Staphylococcus aureus indicated that CvDef1 had much better antimicrobial ability than ampicillin, making it a potential candidate for practical use. Transmission electron microscopic (TEM) examination of CvDef1-treated S. aureus cells showed extensive damage to the cell membranes. Our results revealed the basic properties of three defensins in C. vestalis for the first time, which may pave the way for further study of the functions of defensins in parasitism and innate immunity of C. vestalis. |
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Keywords: | Defensin Endoparasitoid wasp Developmental stage Innate immunity Antimicrobial peptide Antimicrobial activity |
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