Divergent physiological and molecular responses of light- and iron-limited Southern Ocean phytoplankton

• Published in: Limnology and Oceanography Letters
• Main Authors: Andrew, SM, Strzepek, RF, Whitney, SM, Chow, WS, Ellwood, MJ
• Format: Article in Journal/Newspaper
• Language: English
• Published: John Wiley & Sons Inc 2022
• Subjects: iron; light; physiology; Southern Ocean; phytoplankton; microbial ecology
• Online Access: https://eprints.utas.edu.au/46419/; https://eprints.utas.edu.au/46419/2/148180%20-%20Divergent%20physiological%20and%20molecular%20responses%20of%20light.pdf

It has recently been shown that Southern Ocean phytoplankton species have evolved to optimize their light-harvesting potential without increasing the high iron-requiring proteins used for photosynthesis. We measured molecular and physiological responses of phytoplankton cultures under a combination of iron and light conditions. While iron-replete cultures mostly increased biovolume, photochemical efficiency (Fv/Fm) and the relative abundance of photosystem II (PSII) and Cytochrome b6f protein compared to iron-limited cultures, light also regulated cellular chlorophyll a content and played a role in controlling PSII protein abundance. Investment of protein resources into the carbon fixing enzyme Ribulose 1,5-bisphosphate carboxylase oxygenase (Rubisco) was species-specific, but increased growth rates correlated with increased investment into Rubisco for all species. Our results suggest that Proboscia inermis uses a divergent molecular strategy to compete for nutrients, light, and CO2 in the Southern Ocean.