The diatom Fragilariopsis cylindrus: A model alga to understand cold‐adapted life

Abstract

Conducting research in polar regions is still a significant challenge because of issues with access and working at subfreezing temperatures. Yet, polar environments are home to significant biological diversity, including diverse primary producers. As photosynthesis on land is limited by permafrost and glaciers, marine phytoplankton groups and, especially, diatoms underpin most of the polar food web (Boyd, 2002;Horner et al., 1992;Smetacek, 1999). Diatoms can cope well with low temperatures and significant seasonality, including the long and dark polar winter (McMinn & Martin, 2013). Although global warming appears to diminish the dominance of diatoms in polar oceans (Ardyna & Arrigo, 2020), diatoms are still a significant driving force in terms of underpinning polar food webs and global biogeochemical cycles (Hop et al., 2020).Fragilariopsis cylindrus is an obligately coldadapted (psychrophilic) pennate diatom found in Arctic and Antarctic seawater and sea ice (Figure 1). It is considered a keystone species for polar waters, thriving under diverse polar conditions and forming blooms in sea ice and at the sea-ice edge (Hop et al., 2020). As a polar indicator species, F. cylindrus actively thrives under high salinity, low temperatures, and semienclosed sea-ice systems (Kang & Fryxell, 1992). In this perspective paper, we provide a brief overview on the work that has been done so far on F. cylindrus and discuss its role as a model alga to understand coldadapted life.The genome of Fragilariopsis cylindrus, published in 2017 (Mock et al., 2017), was the first sequence of a cold-adapted eukaryote. In recent years, whole genome sequences of several additional polar algal species have followed suit, such as genomes from dinoflagellates, chlorophytes, and prasinophytes (

Declines in ice cover are accompanied by light limitation responses and community change in freshwater diatoms

“…Phylogenetic analyses indicated that diatoms horizontally acquired FAS1 from bacteria, as there is evidence for at least six instances of horizontal gene transfer within our analysis ( Figure 7D ). Broadly, the FAS1 domain is widely distributed in diatoms, with ~140 marine and freshwater diatoms found to contain this protein domain, including the model cold-adapted diatom Fragilariopsis cylindrus [ 69 ].…”

“…More broadly, our phylogenetic analyses suggest this fasciclin-mediated rafting hypothesis may not be unique to Lake Erie diatoms alone. Fasciclins were identified in ~140 marine and freshwater diatoms, including the model polar marine diatom F. cylindrus [ 69 ]. Hence, this further implies an ecophysiological role exists for these proteins in the globally frigid waters, which in turn indicates that further research is required regarding the role of fasciclins within polar aquatic systems and psychrophilic organisms broadly, especially when considering the rapid global decline in ice cover.…”

Phaeodactylum tricornutum: An established model species for diatom molecular research and an emerging chassis for algal synthetic biology

“…Phaeodactylum tricornutum has proven highly successful in revealing fundamental aspects of diatom biology that are relevant to many species. Diatom research is now greatly benefitting from the establishment of new ecologically relevant model systems (Ferrante et al, 2023;Otte et al, 2023;Poulsen & Kröger, 2023). Without doubt, the fundamental and practical insights gained and still to come through the study of P. tricornutum will support comparative investigations, essential for addressing the significance of diatom diversity in the context of adaptation and evolution.…”