Development of genomic tools for the moss Bryum argenteum and its comparative analysis with other published moss genomes

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Bryophytes were the first plants to colonize land approximately 500 million years ago. Liverworts, hornworts, and mosses make up the bryophytes and out of these mosses are the most diverse group of non-vascular land plants. Mosses are small and seed-free plants that lack roots and exhibit tolerance to abiotic stresses such as changes in temperature, drought, and heavy metals. However, only a few moss genomes have been studied so far as compared to angiosperms. To better understand the biology of the moss Bryum argentum also called the Silvery-thread moss we used short and long read data obtained from Illumina and Oxford Nanopore respectively. A hybrid genome assembly was prepared using long and short DNA read. A genome size of 308.8 Mbp was generated which had 37.47% of repetitive count and 48,490 protein-coding gene predictions. A synteny analysis of the protein-coding genes with closely related moss species suggested that there has been a major change in the orientation of genes in Bryales after their divergence from Dicranales. Species tree constructed from all available moss genomes agreed with the previously published moss phylogenies. The evolutionary pattern of genes in B. argenteum suggested positive selection or reduced purifying selection which could be because of a large number of gene duplications predicted in the moss. A gene ontology enrichment analysis suggested a different pattern of selection for the genes involved in nitrogen metabolism. The genomic data generated will help in better understanding of B. argenteum, its evolutionary genomics and will be valuable to study different traits of the moss such as heavy metal and desiccation tolerance. Moreover, this will also help us understand the evolution of land plants by studying one more moss genome.

Bryophtes, Monoicous, Dioicous