Green fluorescent proteins show divergent patterns among species and strains of Porites from the Great Barrier Reef

GFP-like and RFP-like proteins serve diverse functional roles in corals, including photoprotection, prey capture, and algal symbiont attraction. This study investigated the diversity of biofluorescence patterns in 27 coral colonies of Porites cf. lutea and P. cf. lobata from the Great Barrier Reef, Australia. We used comparative methods to characterize the extant fluorescence patterns under blue and green light for excitation, their relationship to the Porites phylogeny built using host animal 18S-28S rDNA sequence data, with a focus on intraspecies variation. We also studied the impact of thermal stress on GFP-like and RFP-like fluorescence in a single coral genotype to assess stability of the observed signal. We identified six broad fluorescence patterns: star, uniform, absent, tentacles, oral region, and tentacle tips. Population analyses demonstrate that a single lineage of Porites may express divergent and distinct GFP-like patterns that are shared by all polyps in a colony. This suggests that biofluorescent proteins may confer an array of adaptive functions that allow Porites species to thrive in different ecosystems under different stressors. The reorganisation of both GFP-like and RFP-like distributions to uniform patterning under thermal stress suggests these proteins may provide a biomarker of thermal stress. Thus, the potential for GFP and RFP screening as a non-invasive tool to assess reef health and adaptive responses warrants further investigation, particularly in the context of climate change-driven stress events.