Equatorial to Polar genomic variability of the microalgae Bathycoccus prasinos

Abstract

The importance of marine phytoplankton in food webs and biogeochemical cycles makes the study of prokaryotic and eukaryotic phytoplankton species essential to understand changes in the global ecosystem. As plankton is transported by ocean currents, its community composition varies. Some species are abundant in contrasting environments, which raises the question of the genomic basis of their adaptation. Here we exploit the cosmopolitan distribution of the eukaryotic picoalgae Bathycoccus prasinos to investigate its genomic variations among temperate and polar populations. Using multiple metagenomic data, we found that ~5% of genomic positions of B. prasinos are variable, with an overwhelming majority of biallelic patterns. Cold and temperate waters are clearly associated with changes in variant occurrences including striking differences at some non-synonymous positions of several genes. Data from transitional waters showed more balanced polymorphism at most of these positions. The comparison of mesophilic and psychrophilic gene variants of this species suggests that its adaptation to cold waters may involve few amino acid changes at positions of protein structures critical for physical and functional properties. These results provide new insights into the genomic diversity and temperature-associated amino acid changes of a cosmopolitan eukaryotic planktonic species.

Whole-genome scanning reveals environmental selection mechanisms that shape diversity in populations of the epipelagic diatom Chaetoceros

“…MAGs must furthermore include information about assembly quality, level of contamination and completeness, to enable robust comparisons between studies [47]. The exploration of marine phytoplankton population genomics using metagenomes has only just begun, with a few pioneering studies focused on the Mamiellales genera Bathycoccus, Micromonas, and Ostreococcus [78,79]. In line with these, the present study aimed to generate a portrait of the diversity landscape among natural Chaetoceros populations and to bridge the gap between diatom genomes, physiological responses, and population genomics by tearingAU : PleasecheckifthechangesmadeinthesentenceInlinewiththese; thepresentstudyaimedto apart the correlation of geographical distance and environmental factors with population structure.…”

Whole-genome scanning reveals selection mechanisms in epipelagic Chaetoceros diatom populations

“…Metagenome-assembled genomes must furthermore include information about assembly quality, level of contamination and completeness, to enable robust comparisons between studies (Bowers et al 2017). The exploration of marine phytoplankton population genomics using metagenomes has only just begun, with a few pioneering studies focused on the Mamiellales genera Bathycoccus , Micromonas and Ostreococcus (Leconte et al 2020; Leconte et al 2021). In line with these, the present study aimed to generate a portrait of the diversity landscape among natural Chaetoceros populations and to bridge the gap between diatom genomes, physiological responses and population genomics by teasing apart the correlation of geographical distance and environmental factors with population structure.…”

Changes in functional composition and gene expression in eukaryotic plankton at the Atlantic-Arctic Polar front

“…While the transcriptional response we report seem critical to adapt it might not be sufficient to explain the survival of persisting algae. Indeed organisms might also need to adapt by directly changing the sequence of their proteins as recently suggested in Bathycoccus ( 11 ) and in the SAR supergroup ( 52 ) or by mechanisms such as allele specific expression recently reported in the copepod Oithona similis ( 53 ) and in the diatom Fragilariopsis cylindrus ( 27 ). Therefore, the signal we observe is probably due to a mix of acclimation and adaptation responses that we can’t disentangle here.…”

“…Many studies based either on satellite ( 6, 7 ) or genomic data ( 4, 8, 9 ) revealed a mainly latitudinal and temperature driven biogeographical partitioning of the oceans. While some species have strictly defined environmental niches ( 4, 10 ), some display cosmopolitan biogeographies, such as Bathycoccus prasinos which is present in both polar and temperate oceans ( 11 ) or Pelagomonas calceolata that is cosmopolitan in all except polar oceans ( 12 ).…”