Molecular Characterisation and Expression of Heat Shock Protein Gene (HSP70) inTribolium castaneumAdults Under Different Environmental Stressors

Abstract

Insects react to temperature variation, chemical and physical stressors by synthesis of a set of proteins known as heat shock proteins (HSPs). In this study, a cDNA gene coding a heat shock protein70 (HSP70) from Tribolium castaneum has been sequenced and characterised from adult beetles. The deduced peptide sequence ORF (Open Reading Frame) of HSP70 had 220 amino acid residues, had a calculated molecular mass of 24.30 kDa and an isoelectric point (Ip) of 6.85. T. castaneum HSP70 showed high identities with other coleopteran HSP70 by BLAST search in NCBI. Multiple sequence alignment at both nucleotide and amino acid levels were performed showing conserved regions between HSP70 and other heat shock proteins isolated from insects. Phylogenetic analysis was constructed by neighbour-joining distance analysis showing that HSP70 putative peptide was clustered with other heat shock protein from the same species. 3-D structure modelling of HSP70 was employed. Transcriptional profiles of HSP70 were determined by quantitative RT-PCR analysis after adult beetles were exposed to 45 °C, 4 °C and novaluron (insect growth regulator) for 60 min as physical and chemical stressors. HSP70 transcript was up-regulated at the highest level when adults were exposed to 45 °C for 60 min. In contrast, HSP70 transcript was down-regulated when adults were exposed to 4 °C and novaluron for 60 min.