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Researchers achieve highest-quality moss genome assembly to date

A research team has achieved a gapless assembly of Syntrichia caninervis's genome, totaling 323.44 Mbp with an N50 value of 24.41 Mbp and a single-base accuracy exceeding 99.999%, making it the highest-quality moss genome reported to date. This work is in the Plant Biotechnology Journal.

Syntrichia caninervis, a crucial moss species for maintaining the ecological balance in the Gurbantunggut Desert, has gained attention as a model for studying desiccation tolerance.

To assemble its high-quality genome, Prof. Zhang Daoyuan's team from the Xinjiang Institute of Ecology and Geography (XIEG) of the Chinese Academy of Sciences developed a monoclonal tissue culture system for Syntrichia caninervis, successfully obtaining its pure strains.

The researchers also obtained the complete genome sequence of the moss's endosymbiont, Paenibacillus sp., by employing third-generation sequencing technologies such as PacBio and Oxford Nanopore, mitigating the effect of endosymbiotic sequence contamination in the genome assembly of Syntrichia caninervis.

The Telomere-to-Telomere (T2T) genome of Syntrichia caninervis represents the most complete reference genome for the species. It surpasses the previous Mojave Desert genome by assembling more than 30 Mbp of previously missing sequences, filling more than 20,000 chromosomal gaps, and annotating more than 1,500 additional protein-coding genes.

Notably, the study revealed new structural variations found on sex chromosomes from differing ecotypes in the Gurbantunggut and Mojave Deserts.

In addition, the latest genome version identified 677 transcription factor genes—135 more than before—and fully annotated previously unclassified factors, thereby enriching the transcriptional regulatory gene pool. The transcriptomic mapping rates improved by 10% compared to the previous version, and key desiccation-related gene families, such as late embryogenesis abundant (LEA), showed increased tandem repeat patterns.

This enhanced genome provides a robust foundation for future research in population genomics and gene function.

This study confirmed that the centromeric structure of Syntrichia caninervis is dominated by Copia transposons, contrasting with angiosperms. This study provides valuable insights into the evolutionary patterns of centromeric structures in land plants.