{Reference Type}: Journal Article
{Title}: Red algae acclimate to low light by modifying phycobilisome composition to maintain efficient light harvesting.
{Author}: Voerman SE;Ruseckas A;Turnbull GA;Samuel IDW;Burdett HL;
{Journal}: BMC Biol
{Volume}: 20
{Issue}: 1
{Year}: 12 2022 27
{Factor}: 7.364
{DOI}: 10.1186/s12915-022-01480-3
{Abstract}: Despite a global prevalence of photosynthetic organisms in the ocean's mesophotic zone (30-200+ m depth), the mechanisms that enable photosynthesis to proceed in this low light environment are poorly defined. Red coralline algae are the deepest known marine benthic macroalgae - here we investigated the light harvesting mechanism and mesophotic acclimatory response of the red coralline alga Lithothamnion glaciale.<BR>Following initial absorption by phycourobilin and phycoerythrobilin in phycoerythrin, energy was transferred from the phycobilisome to photosystems I and II within 120 ps. This enabled delivery of 94% of excitations to reaction centres. Low light intensity, and to a lesser extent a mesophotic spectrum, caused significant acclimatory change in chromophores and biliproteins, including a 10% increase in phycoerythrin light harvesting capacity and a 20% reduction in chlorophyll-a concentration and photon requirements for photosystems I and II. The rate of energy transfer remained consistent across experimental treatments, indicating an acclimatory response that maintains energy transfer.<BR>Our results demonstrate that responsive light harvesting by phycobilisomes and photosystem functional acclimation are key to red algal success in the mesophotic zone.