Genome-wide comparative analysis of theSHSP,HSP60/10andHSP90genes reveals differential heat stress responses in estivation of the sea cucumberApostichopus japonicus

Small HSP (SHSP), HSP60/10 and HSP90 are subgroups of heat shock proteins and play important roles in cytoprotective, housekeeping and apoptosis regulatory functions. These proteins are always involved in the response to stressful stimuli, especially heat stress. In this study, 10 SHSPs, two HSP60/10s and three HSP90s were identified and systematically characterized from the transcriptome and genome of the sea cucumber Apostichopus japonicus. According to the results of phylogenetic and syntenic analyses, although the AjSHSPs were less evolved in that they did not occupy the specific domain, there was a mild expansion of AjSHSPs that made the sea cucumber the species that had the most SHSPs among the invertebrate species that were evaluated in this study. The expression of five copies in Class I SHSPs (AjHSP24.3, AjHSP25.5, AjHSP25.6, AjHSP26.1 and AjHSP29.8) tended to be most regulated in estivation in adult individuals, while they exhibited differential patterns in juvenile individuals, suggesting their critical roles in the response to estivation and that different strategies were used in the response to chronic heat shock between adult and juvenile individuals. AjHSP60/10s and AjHSP90s were found to be relatively mildly regulated and were suggested to play additional roles in housekeeping. Together, these findings may provide an early insight into the involvement of SHSPs, HSP60/10s and HSP90s in estivation of marine invertebrate.