Expression and Localization of a Testis-Specific Heat Shock Protein (CfHSP70-2) During Spermatogenesis in the Spruce Budworm, Choristoneura fumiferana (Clem.).

Heat shock proteins (HSPs) are essential across several insect species for adaptation to environmental stressors. Most pest insects experience fertilization concurrently with summer heat extremes, which mostly affect male testis development and spermatogenesis; although the molecular mechanisms involved are unclear. Several HSPs are exclusive to the testis in several insects, but their functional roles remain unclear. In this study, we identified a testis-specific ATP-dependent HSP, CfHSP70-2 in the spruce budworm (SBW), Choristoneura fumiferana. Reverse transcript-qualitative polymerase chain reaction and western blotting were performed to detect the tissue-and developmental stage-specific expression of CfHSP70-2. In addition, the effects of various stressors on CfHSP70-2 expression in the testes were examined. Importantly, CfHSP70-2 was first detected in the late pupal stages and peaked in the adult stages. Heating, starvation, or chemical HSP activators did not stimulate CfHSP70-2 expression. Immunohistochemical staining revealed that CfHSP70-2 was primarily found in round spermatids at the late pupal and adult stages. The potential function role of CfHSP70-2 in spermatogenesis in SBW is discussed.