Genomic variation in green macroalgae of the genus Ulva

Coastal ecosystems are susceptible to over proliferation of bloom-forming macroalgae due to increases in shoreline development worldwide. One prominent bloom-forming clade, the genus Ulva, offers promising model organisms for understanding these environmentally damaging events and plays a developing role in industry as biomass feedstocks for renewable fuel production. This thesis investigates the landscape of genetic variation among cryptic Ulva species within this clade. Two novel nuclear genomic assemblies were created from field collected specimens to expand our understanding of species relationships in this genus. Comparative analyses with the first published Ulva genome, U. mutabilis, indicate a high degree of variability between species, while intraspecific and intergenic comparisons mirror these findings. Proteome size alone is a poor predictor of carbohydrate sulfotransferase levels and cell wall sulfotransferases are elevated in marine chlorophytes as compared to freshwater counterparts. These correlative findings strongly suggest sulfotransferases are an adaptation benefiting stress tolerance in marine macroalgae. Investigation of orthologous genes among more diverse chlorophytes present unique findings of horizontal gene transfer and gene expansion in Ulva sulfotransferase activity. A gene family containing sulfotransferases is unique to and expanded in Ulva among other chlorophytes. These datasets are rich with data and the prospects for further comparative analysis are strong. Specifically, more direct experimental confirmation of sulfotransferase stress tolerance would add validation to these findings. Further investigation of genetic relationships among Ulva species would add context to this developing field.