Characterization of the heat shock protein 90 gene of Heterorhabditis bacteriophora and its expression in response to different temperature stress.

Heat shock proteins belong to a protein family that are rapidly synthesized in response to a series of environmental stressors. Among all HSPs, HSP90 is the most conserved and abundant in cells and is involved in response to temperature stress. Temperature affects life-stage development and behaviour of entomopathogenic nematodes, with different species and strains having optimum temperatures for penetration, feeding, survival and reproduction. Thus, temperature is an important factor in controlling generation time of EPN. In the present study, the full-length cDNA and the corresponding gene of HSP90 of Heterorhabditis bacteriophora were cloned and sequenced and its expression in response to three different temperatures was also investigated. The full-length Hb-hsp90 cDNA contained an ORF of 2139 bp encoding a polypeptide of 713 amino acids. The deduced amino acid sequence of Hb-Hsp90 showed high similarity with other known HSP90s. The gene consists of 12 exons and 11 introns, an expanded gene structure compared to other nematode hsp90 genes. Hb-hsp90 gene was constitutively expressed in all developmental stages of H. bacteriophora but at higher level in adult males and females. Larvae of Galleria mellonella were infected with infective juveniles (IJs) of H. bacteriophora and exposed at 12°C, 23°C and 30°C for 10 days in order to explore the impact of adverse temperature on reproduction and infectivity of H. bacteriophora and on Hb-hsp90 expression in IJs and adult stages. Results obtained in this study are reported and discussed.