Identifications of cytochrome c and Apaf-1 and their mRNA expressions under heat stress in insecticide-susceptible and -resistant Plutella xylostella (Lepidoptera: Plutellidae)

Abstract

To study the component and gene expressions of apoptosome in the mitochondrial-associated apoptotic pathway, cytochrome c and Apaf-1 were identified in the diamondback moth (DBM), Plutella xylostella, collected from Fuzhou, China. The full-length cDNA of cytochrome c comprised 873 bp, including a 327 bp ORF encoding a putative protein of 108 amino acids. Two full-length cDNAs of Apaf-1, Apaf-1a and Apaf-1b, were identified. Apaf-1a shared the same region of 5'-UTR (5'-untranslated region) (172 bp) and ORF (4,647 bp) of cDNA, but was 73 bp longer than Apaf-1b in the region of 3'-UTR of the cDNA. The ORF of Apaf-1a and Apaf-1b encoded a putative protein of 1,548 amino acids and shared 100% identity. No significant up-regulation of cytochrome c mRNA expression was found in both the chlorpyrifos-resistant (RR) and chlorpyrifos-susceptible (SS) DBM. Compared with the control (at 25°C for 3 h), mRNA transcript levels of Apaf-1a and Apaf-1b increased with the increase of temperature and were significantly higher at 37, 42, 47 and 50°C than at 25 and 33.5°C in RR DBM. However, the extent of up-regulation expression of Apaf-1a and Apaf-1b in SS DBM was slight under heat stress except at 42°C. In general, significantly higher increase in the mRNA transcript level of Apaf-1a and Apaf-1b was found in RR DBM than in SS DBM. It has been suggested that significantly higher expression of caspase-7 and lower biological fitness occurs in RR DBM under heat stress, a suggestion confirmed in our previous publications, and a result which might be associated with their higher up-regulation expression of Apaf-1a and Apaf-1b.

Keywords

• lepidoptera
• plutellidae
• plutella xylostella
• diamondback moth
• chlorpyrifos-resistant and -susceptible
• cytochrome c
• apaf-1
• fitness