The genome of the Arctic snow alga Limnomonas spitsbergensis (Chlamydomonadales)

Abstract

Snow-algae are a diverse group of extremophilic microeukaryotes found on melting polar and alpine snowfields. They play an important role in the microbial ecology of the cryosphere, and their propagation on snow and ice surfaces may in part accelerate climate-induced melting of these systems. High quality snow-algae genomes are needed for studies on their unique physiology, adaptive mechanisms and genome evolution under multiple forms of stress, including cold temperatures and intense sunlight. Here we assembled and annotated the genome of Limnomonas spitsbergensis, a cryophilic biciliate green alga originally isolated from melting snow on Svalbard, in the Arctic. The L. spitsbergensis genome assembly is based primarily on the use of PacBio long reads and secondly Illumina short reads, with an assembly size of 260.248 Mb in 124 contigs. A combination of three alternative annotation strategies were used including protein homology, RNA-seq evidence and PacBio full length transcript isoforms. The best merged set of annotations identified 18,277 protein-coding genes, which were 95.2% complete based on BUSCO analysis. We also provide the annotated mitogenome, which is a relatively large 77.942 kb circular mapping sequence containing extensive repeats. The L. spitsbergensis genome will provide a new resource for research on snow-algae adaptation, behavior and natural selection in unique, low-temperature terrestrial environments that are under threat from climate change.

Long-Read–Based Hybrid Genome Assembly and Annotation of Snow Algal Strain CCCryo 101-99 (cf. Sphaerocystis sp., Chlamydomonadales)

“…Molecular studies, particularly metabarcoding and metagenomic approaches, have only recently provided the first critical insights into polar biodiversity and evolution and adaptation to permanently cold environments ( Clark et al 2023 ). However, most work has focused on marine settings, and there are only a few available psychrophilic algae genomes ( Blanc et al 2012 ; Mock et al 2017 ; Zhang et al 2020 , 2021 ; Hulatt et al 2024 ). This hampers our ability to understand their evolutionary history, metabolic potential, and cellular responses and to better address their potential roles in future global warming climate scenarios.…”