Mitotic recombination between homologous chromosomes drives genomic diversity in diatoms

Potential for Biomass Production and Remediation by Cultivation of the Marine Model Diatom Phaeodactylum tricornutum in Oil Field Produced Wastewater Media

“…Cultivation experiments further show that P. tricornutum strains successfully adapt to these low-salinity media over the course of several months. This result is in alignment with a recent study by Bulankova et al (2021) showing the exceptional ability of P. tricornutum to adapt to stressful environments through genomic evolution. Together this study raises questions about the gene repertoires underlying P. tricornutum's capacity to grow on oil field PW and its bioremediation of elements like fluorine and copper.…”

“…At first sight, given that P. tricornutum is a non-sexual species, it is surprising that genetic adaptation would have occurred so rapidly. Recently, however, it was shown that under stressful conditions, P. tricornutum executes mitotic homologous recombination events between homologous chromosomes at a rate more than 10 times higher than that of the yeast S. cerevisiae [61]. The authors of that study suggest that this process underlies the phenotypic plasticity that led to its adaptation to stressful conditions, even in monoclonal strains after just one month of exposure to the stressor.…”

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

“…By leveraging metagenomes reconstructed through the Tara Oceans expeditions, we drew a comprehensive landscape of the genetic diversity among different populations of this genus and were able to address their level of gene flow through an analysis of their population structure. The levels of micro-diversity observed here, ranging from 0.63% to a maximum of 2.34%, are in line with previous analyses conducted on natural populations of the diatom Fragilariopsis cylindrus from Tara Oceans station 86, which displayed ~2% SNV density (Bulankova et al 2021). The observation of elevated genetic differences among populations from the same species means that despite their high potential dispersal, Chaetoceros diatoms can express significant levels of divergence.…”

“…Collectively, these factors may constitute a limit to the understanding of metabolism and locally relevant genomic functions. Moreover, interrogating Tara Oceans metagenomes with the Fragilariopsis cylindrus CCMP 1102 genome showed enough read coverage for only one sampling station, further exemplifying the divergence between laboratory strains and natural populations (Bulankova et al 2021). While cultivating strains in the lab is a necessary first step to gaining insights into their fundamental ecology, accessing the genomes of organisms directly from their environment is key to fully understanding their role within natural communities and their responses to environmental fluctuations.…”

“…This chimeric origin led to specific physiological innovations, such as silicon utilisation for cell protection, efficient nutrient uptake systems allowing rapid responses to environmental fluctuations, a functional urea cycle and potential carbon concentration mechanisms (Armbrust et al 2004; Bowler et al 2008; Pierella Karlusich, Bowler, et al 2021). In contrast to these genetically-encoded functions, diatom genomes themselves appear to display a wide variety of dynamics, through specific transposable elements in the model diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum (Armbrust et al 2004; Maumus et al 2009), alternative splicing (Rastogi et al 2018), as well as gene copy number variation and mitotic recombination between homologous chromosomes (Bulankova et al 2021). Altogether, these characteristics likely fuel diatom diversity, leading to rapid diversification rates (Bowler et al 2008) while increasing their ability to respond to changing environmental conditions.…”