Molecular and Physiological Acclimation to Low Light and Iron Scarcity in Globally Abundant Oceanic Pelagophyte Article Swipe
YOU?
·
· 2025
· Open Access
·
· DOI: https://doi.org/10.21203/rs.3.rs-6701642/v1
· OA: W4413086141
<title>Abstract</title> <italic>Pelagomonas calceolata</italic> is a widely distributed marine alga and is among the most numerous eukaryotes on Earth. It is abundant in subsurface chlorophyll maximum layer (SCML) communities where it can be responsible for a majority of nitrate assimilation. Growth in these communities is frequently limited by the lack of iron (Fe), and no eukaryotic phytoplankton species has been shown to require less Fe than <italic>P. calceolata.</italic> SCML communities are also light limited, resulting in an increased need for Fe-rich photosynthetic proteins. Consequently, to survive and compete in these SCML environments calls for an Fe/light co-limitation specialist. To understand the strategies behind <italic>P. calceolata</italic>’s success, we profiled this organism’s physiology and gene expression as it experiences Fe/light co-limitation. Our study describes the cellular changes under steady-state Fe limitation and the short-term responses to Fe resupply. Our culture experiments revealed that <italic>P. calceolata</italic> maintains exceptionally low Fe:C ratios across conditions and dynamically regulates iron-sparing strategies such as flavodoxin expression and substitution of metal-rich proteins. Furthermore, coupling environmental gene expression with culture-based profiles showed that Fe- and light-responsive genes identified in the lab were strongly enriched in SCML metatranscriptomes, indicating that <italic>P. calceolata</italic> expresses these adaptations <italic>in situ</italic>. These results demonstrate low Fe tolerance as a key adaptation enabling <italic>P. calceolata</italic> to thrive in light-limited marine environments and highlight its broader role in oceanic carbon and nitrogen cycling.
