Project description:The smallest phytoplankton species are key actors in oceans biogeochemical cycling and their abundance and distribution are affected with global environmental changes. Among them, algae of the Pelagophyceae class encompass coastal species causative of harmful algal blooms while others are cosmopolitan and abundant. The lack of genomic reference in this lineage is a main limitation to study its ecological importance. Here, we analysed Pelagomonas calceolata relative abundance, ecological niche and potential for the adaptation in all oceans using a complete chromosome-scale assembled genome sequence. Our results show that P. calceolata is one of the most abundant eukaryotic species in the oceans with a relative abundance favoured by high temperature, low-light and iron-poor conditions. Climate change projections based on its relative abundance suggest an extension of the P. calceolata habitat toward the poles at the end of this century. Finally, we observed a specific gene repertoire and expression level variations potentially explaining its ecological success in low-iron and low-nitrate environments. Collectively, these findings reveal the ecological importance of P. calceolata and lay the foundation for a global scale analysis of the adaptation and acclimation strategies of this small phytoplankton in a changing environment.
| S-EPMC9481584 | biostudies-literature
Project description:Pelagomonas calceolata CCMP1756 (Genome sequencing and assembly)
Project description:Pelagomonas calceolata 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 P. calceolata. 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 P. calceolata’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 P. calceolata 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 P. calceolata expresses these adaptations in situ. These results demonstrate low Fe tolerance as a key adaptation enabling P. calceolata to thrive in light-limited marine environments and highlight its broader role in oceanic carbon and nitrogen cycling.
