Endophytic symbiont yeasts associated with the Antarctic angiosperms Deschampsia antarctica and Colobanthus quitensis

Fungal diversity in Antarctic seems to be greater than what is known and remains largely unexplored. In this study, we identified the endophytic symbiont yeasts associated with leaves of the angiosperms Deschampsia antarctica and Colobanthus quitensis living on King George Island, Antarctica using a culture-based approach. One hundred and twelve yeast isolates were obtained from the tissue of the different plants sampled. These yeasts were identified using sequencing of the D1/D2 domains of the LSU region of the rRNA gene as Cryptococcus victoriae, Cystobasidium laryngis, Rhodotorula mucilaginosa, Sporidiobolus ruineniae and Leucosporidium aff. golubevii. The psychrophilic yeast C. victoriae was the most abundant species associated with the two angiosperms. Cystobasidium laryngis occurs only in the leaves of D. antarctica. In contrast, R. mucilaginosa, S. ruineniae and L. aff. golubevii occurred only in C. quitensis. Phylogenetic analysis indicates the Antarctic endophytic yeast strains are closely related to taxa obtained from substrates located in different habitats of the world. However, the endophytic yeast C. victoriae was closely related to psychrophilic taxa isolated from Antarctica, but also from the Arctic, Alpine and Himalayan environments. The abundance of endophytic yeasts associated with Antarctic angiosperms suggests a possible symbiotic relationship with their plant hosts, which may provide shelter and growing conditions suitable for the yeasts' survival, dispersal and colonization other Antarctic environments. In contrast, the endophytic yeasts might directly or indirectly promote the fitness of their host plants by producing metabolites beneficial to plant survival in the extreme environments of Antarctica.