The regulation of inhibitor of apoptosis proteins (IAPs) during the apoptosis of Cotesia chilonis.

Inhibitor of apoptosis proteins (IAPs) are crucial components of apoptosis that perform vital roles in the regulation of caspase activity in organisms. In this study, two IAPs genes were identified from Cotesia chilonis, the dominant parasitic wasp of Chilo suppressalis. CcIAP1 gene is a typical IAP and contains two BIR domains and a RING domain, whereas CcIAP gene is an atypical IAP1 only containing two BIR domains. Phylogenetic analysis indicated that CcIAP1 and CcIAP were grouped with other Hymenopteran IAPs and IAP1 in C. suppressalis. Real-time quantitative PCR revealed that CcIAP1 and CcIAP genes were both highly induced at -6°C and 30°C, and expression was highest at the third instar stage. The expression of CcIAP1 and CcIAP genes were significantly induced during parasitism of C. suppressalis, and the 7-d time point resulted in the highest expression levels for both genes, in which was an advanced stage of larval development of C. chilonis. RNAi experiments showed that CcIAP1 gene was the key IAP in the regulation of apoptosis of C. chilonis and its host. In conclusion, CcIAP1 and CcIAP correlate with the development of C. chilonis and their responses to temperature stress.

Identification and physiological function of CsPrip, a new aquaporin in Chilo suppressalis.

Aquaporin (AQP) transport solutes across cell membranes in both unicellular and multicellular organisms. In this study, the aquaporin CsPrip was identified in Chilo suppressalis, an important pest of rice. CsPrip was comprised of two variants, CsPrip_v1 and CsPrip_v2; the former variant was <103 bp was shorter than the latter, although both exhibited the same open reading frame (ORF). Transmembrane topology and protein structure analyses showed that CsPrip retained the conserved features of water-selective insect AQPs, including six transmembrane domains, two conserved hydrophobic asparagine-proline-alanine motifs and the aromatic/arginine constriction region. Expression in Xenopus oocytes revealed that CsPrip preferentially transported water and urea instead of trehalose and glycerol. The CsPrip transcript was expressed in multiple organs and tissues of C. suppressalis larvae and was most abundant in the hindgut and Malpighian tubules. CsPrip transcription was highest in male adults and was relatively stable throughout development. CsPrip expression in larvae was significantly altered by thermal stress, and relative humidity levels impacted CsPrip transcription in 3rd and 5th instar larvae. This study confirms that the aquaporin CsPrip performs multiple critical functions in maintaining water equilibrium in C. suppressalis.

Comparison of morphology, development and expression patterns of hsf and hsp11.0 of Cotesia chilonis under normal and high temperature.

Cotesia chilonis (Munakata) is the dominant parasitic wasp of the rice pest, Chilo suppressalis (Walker), and is a valuable parasitic wasp for the prevention and control of C. suppressalis. In this study, developmental indicators and expression of Cchsp11.0 (heat shock protein 11.0) and Cchsf (heat shock factor) were compared for C. chilonis at 27 °C and 36 °C. Developmental duration, morphology, emergence rate, and number of C. chilonis offspring were shortened at 36 °C while the ratio of females to males increased. Cchsp11.0 and Cchsf were highly expressed in the 1st instar stage at 36 °C, and Cchsp11.0 expression gradually decreased as C. chilonis matured; Cchsf expression was not correlated with Cchsp11.0 expression. Compared with 27 °C, the expression pattern of Cchsp11.0 and Cchsf was also not consistent, and Cchsp11.0 expression increased significantly at the adult stage. In conclusion, mildly high temperatures impact growth, development and reproduction of C. chilonis and stimulate the expression of Cchsp11.0 and Cchsf, and Cchsp11.0 and Cchsf play different roles in different developmental stages of C. chilonis at normal and high temperature.

Molecular Characterization of Heat-Induced HSP11.0 and Master-Regulator HSF from Cotesia chilonis and Their Consistent Response to Heat Stress.

Small heat shock proteins (sHSPs) are members of the heat shock protein (HSP) family that play an important role in temperature stress, and heat shock factors (HSFs) are transcriptional activators that regulate HSP expression. Cotesia chilonis, the major endoparasitoid of Chilo suppressalis, modulates the C. suppressalis population in the field. In this study, we cloned and characterized two genes from C.chilonis: the heat-induced HSP11.0 gene (Cchsp11.0) that consisted of a 306-bp ORF, and the master regulator HSF (Cchsf) containing an 1875-bp ORF. CcHSP11.0 contained a chaperonin cpn10 signature motif that is conserved in other hymenopteran insects. CcHSF is a typical HSF and contains a DNA-binding domain, two hydrophobic heptad repeat domains, and a C-terminal trans-activation domain. Neither Cchsp11.0 or Cchsf contain introns. Real-time quantitative PCR revealed that Cchsp11.0 and Cchsf were highly induced at 36 °C and 6 °C after a 2-h exposure. Overall, the induction of Cchsf was lower than Cchsp11.0 at low temperatures, whereas the opposite was true at high temperatures. In conclusion, both Cchsp11.0 and Cchsf are sensitive to high and low temperature stress, and the expression pattern of the two genes were positively correlated during temperature stress.