Heat-evolved coral photosymbionts exhibit dampened stress responses across distinct physiological contexts.

Abstract

Experimental evolution under elevated temperatures has generated heat-evolved (HE) strains of Symbiodiniaceae that enhance coral bleaching tolerance. However, the biomolecular mechanisms underlying this resilience remain poorly understood. We conducted a laboratory heat-stress experiment and applied synchrotron-based Fourier transform infrared (FTIR) microspectroscopy to examine physiological and biomolecular responses of HE (strain: SS8) and wild-type (strain: WT10) Cladocopium proliferum to thermal stress across three physiological contexts: in hospite, expelled, and cultured. In hospite, both strains exhibited heat-induced increases in free amino acids, phosphorylated compounds, and lipid..