S6-1.7 Thursday, Jan. 5 Exploring the limit of metazoan thermal tolerance via comparative proteomics: Thermally induced expression shifts in hydrothermal vent polychaetes P. sulfincola and P. palmiformis DILLY, GF*; YOUNG, CR; LANE, WS; PANGALINAN, J; GIRGUIS, PR; Harvard University; Mass. Inst. Tech.; Harvard University; DOE Joint Genome Inst.; Harvard University email@example.com
Eukaryotic thermotolerance is challenged at deep-sea vents, where temperatures can surpass 300 °C. Paralvinella sulfincola, an extremely thermotolerant vent polychaete, and Paralvinella palmiformis, a congener with a more modest thermal tolerance, both flourish at vents along the Juan de Fuca Ridge, Washington, USA. We conducted a series of in vivo shipboard, high-pressure experiments on both species to examine physiological adaptations that confer pronounced thermotolerance in P. sulfincola. Quantitative µLC/MS/MS proteomics on 1296 referenced proteins informed by a deeply sequenced EST library, as well as glutathione (GSH - an antioxidant) assays revealed several trends. P. sulfincola exhibited an upregulation in the synthesis and recycling of GSH with increasing temperature, downregulated NADH and succinate dehydrogenases (key enzymes in oxidative phosphorylation) with increasing temperature, but maintained elevated levels of heat shock proteins (HSPs) across treatments. In contrast, P. palmiformis exhibited more classical responses to increasing temperatures, e.g. increasing HSPs. These data, among the first to quantify global protein and antioxidant responses to temperature in an extremely thermotolerant eukaryote, suggest that P. sulfincola’s pronounced thermal tolerance is largely due to its capacity to mitigate oxidative stress via increased synthesis of antioxidants and decreased flux through the mitochondrial electron transport chain. This work informs our knowledge of hydrothermal vent ecology, and more broadly, that oxidative stress may ultimately be the key factor in limiting all metazoan thermotolerance.