Abstract 2204 Subcellular Expression of Heat-Shock Protein in the Coral Holobiont

Heat shock protein(s) (HSPs) are molecular chaperones that predominantly function in de-novo protein folding, preventing protein misfolding and aggregation, thereby maintaining cellular homeostasis. These proteins are overexpressed to combat cellular stress via the regulation of various downstream biochemical pathways. Preliminary studies on heat-stressed reef-building corals and their algal endosymbiont reveal characteristic upregulation of HSPs, specifically HSP 60, HSP 70, and HSP 90, in both partners. These results indicate the direct role of HSPs as a response to thermal stress and its correlation to thermotolerance. While these findings seem promising, the proteins were expressed using bulk tissue homogenates from either coral or algae, thus we currently lack concrete information about the regulation of these proteins at the cellular level, the subcellular location of these proteins, and the differential expression when subjected to varying degrees of environmental stress. Since the coral-algal symbiosis directs several cellular mechanisms in the coral holobiont, the combined response of both partners likely plays a central role in thermotolerance. Our study explores HSPs at the cellular and subcellular level, across different cells- coral, endosymbiont, and coral-endosymbiont combined. We use Fluorescence activated cell sorting (FACS) to separate different cell types, mass-spectrometry based proteomics, and immunofluorescence to analyze and visualize HSP expression in corals and their endosymbionts. These results help us understand the differential expression of HSP and the underlying mechanisms involved in the holobiont's stress response. Better understanding the expression of HSPs is a step towards potentially assisting the upregulation of HSPs for coral enhanced thermotolerance.