The Antarctic Moss Pohlia nutans Genome Provides Insights Into the Evolution of Bryophytes and the Adaptation to Extreme Terrestrial Habitats

The Antarctic continent has extreme natural environment and fragile ecosystem. Mosses are one of the dominant floras in the Antarctic continent. However, their genomic features and adaptation processes to extreme environments remain poorly understood. Here, we assembled the high-quality genome sequence of the Antarctic moss (Pohlia nutans) with 698.20 Mb and 22 chromosomes. We found that the high proportion of repeat sequences and a recent whole-genome duplication (WGD) contribute to the large size genome of P. nutans when compared to other bryophytes. The genome of P. nutans harbors the signatures of massive segmental gene duplications and large expansions of gene families, likely facilitating neofunctionalization. Genomic characteristics that may support the Antarctic lifestyle of this moss comprise expanded gene families involved in phenylpropanoid biosynthesis, unsaturated fatty acid biosynthesis, and plant hormone signal transduction. Additional contributions include the significant expansion and upregulation of several genes encoding DNA photolyase, antioxidant enzymes, flavonoid biosynthesis enzymes, possibly reflecting diverse adaptive strategies. Notably, integrated multi-omic analyses elucidate flavonoid biosynthesis may function as the reactive oxygen species detoxification under UV-B radiation. Our studies provide insight into the unique features of the Antarctic moss genome and their molecular responses to extreme terrestrial environments.

Automated summary

In this study, we assembled the high-quality genome sequence of the Antarctic moss Pohlia nutans and found that it has a larger genome size compared to other bryophytes. The genome of P. nutans contains a high number of gene duplications and expansions of gene families, which may contribute to its adaptation to extreme environments. Genes related to phenylpropanoid biosynthesis, unsaturated fatty acid biosynthesis, and plant hormone signal transduction are expanded in the genome of P. nutans, potentially supporting its lifestyle in Antarctica. Flavonoid biosynthesis may function in detoxification of reactive oxygen species under UV-B radiation, as revealed by integrated multi-omic analyses.