Biology Department Seminar

Understanding how microalgae adapt to fluctuating environments contributes to a better understanding of habitat driven evolution, the potential impacts of climate change on primary producers, and identifies potential targets for exploitation in biomass applications. The halotolerant green algal taxa, Picochlorum (Chloropyta, Trebouxiophycae), have highly reduced and specialized genomes, and are tolerant of fluctuating salinity and light, making Picochlorum a good model to investigate environmental evolution. The broad environmental stress tolerance, robust photosystem II, productivity, and genetic manipulability of Picochlorum make this species an interest for biomass applications. Habitat-specific differences in the salinity stress response in two sister species, Picochlorum oklahomensis (salt plains environment) and Picochlorum SENEW3 (brackish lagoon environment), shows that the coordination of gene regulation may be key to environmental adaptation in species with limited gene inventories. Genome organization of coexpressed genes under salinity shock into 'gene neighborhoods' suggests a role for this genomic architecture in the rapid response to salinity stress in Picochlorum. HGT from prokaryotic origin is an ongoing and dynamic process in this algal lineage involving gene transfer, divergence, loss, and genomic rearrangement. Acquisition of functional relevant genes of bacterial origin contributes to metabolic diversity and salinity tolerance. Overall, the Picochlorum lineage highlights that allelic diversity, coordinated gene regulation and organization, and acquisition of novel functions through HGT contribute to rapid stress responses and niche expansion from a freshwater to hypersaline environment.