Abstract
Heat shock proteins (Hsps) play important roles in the environmental adaptation of various organisms. To explore the functions of Hsps in relation to heat stress and development in Cotesia vestalis, a solitary larval endoparasitoid of Plutella xylostella, four heat shock protein genes, CvHsp40, CvHsc70, CvHsp70 and CvHsp90, were cloned and sequenced from C. vestalis by real-time quantitative PCR and RACE. The cDNA sequence of CvHsp40, CvHsc70, CvHsp70 and CvHsp90 were 1473 bp, 2316 bp, 2279 bp and 2663 bp long, which encode proteins with calculated molecular weights (MW) of 39.1 kDa, 71.2 kDa, 70.1 kDa and 83.3 kDa, respectively. Furthermore, the analysis of genomic DNA confirmed that no introns existed in CvHsp40, CvHsp70 and CvHsp90 while two introns were present in CvHsc70. The amino acid sequence analysis of CvHsps indicated that CvHsp40 is a Type II Hsp40 homolog, CvHsp70 and CvHsc70 are the eukaryotic cytoplasmic Hsp70s, and CvHsp90 is the β-isoform of Hsp90. The divergent transcriptional patterns of CvHsp40, CvHsp70 and CvHsp90 in the different developmental stages suggested that CvHsp transcripts were under different mechanisms of regulation during the development of parasitoid larvae. The dramatic increase of transcripts of CvHsp70 at the third-instar larva coincided with its developmental change in this stage, that is, from inside host to outside host. CvHsp40, CvHsc70 and CvHsp70 showed a trend of sex-specific differences of transcript abundance in the adult stage. All CvHsp transcripts in different developmental stages were significantly induced by heat stress, and the lowest transcript abundances appeared around the temperature 27°C, which probably suggest that this is the most favorable temperature for the development of C. vestalis. Our results suggest that the expression of heat shock proteins reflects to some extent the developmental changes and environmental requirements of insects.
Highlights
The oligophagous solitary larval endoparasitoid, Cotesia vestalis (Haliday) ( = Cotesia plutellae (Kurdjomov))(Hymenoptera: Braconidae) [1], is one of the major natural enemies of the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), one of the very destructive pests of brassica crops in both small-scale and large-scale farming systems worldwide [2,3]
Three conserved regions are found in the deduced amino acid sequence of CvHsp40
Comparing the cDNA and genomic sequences revealed no intron in CvHsp40
Summary
The oligophagous solitary larval endoparasitoid, Cotesia vestalis (Haliday) ( = Cotesia plutellae (Kurdjomov))(Hymenoptera: Braconidae) [1], is one of the major natural enemies of the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), one of the very destructive pests of brassica crops in both small-scale and large-scale farming systems worldwide [2,3]. C. vestalis is distributed in Europe, China, South Africa, Japan, Pakistan, India and Indonesia, and has been introduced from Europe to several countries, including Australia, Commonwealth of Dominica, Fiji, Thailand and the United States and from South Africa to St. Helena [4]. In Hangzhou (China), it is a major parasitoid of P. xylostella, and the highest parasitism (57.2%) of DBM recorded [5]. Shi and Liu reported that the optimal survival temperature for C. vestalis was 25uC [6]. 25uC, the developmental rate increased and the longevity decreased, and no female progeny was produced when the temperature was higher than 35uC
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