Nuclear genome assembly and annotation for the phagotrophic green alga Nephroselmis pyriformis

Abstract

Prasinophytes are a globally distributed, diverse polyphyletic group of photosynthetic green algae, displaying a combination of presumably ancestral traits for the Chloroplastida. The Nephroselmidophyceae is a prasinophyte clade comprising small biflagellate algae that includes the marine mixoplankton Nephroselmis pyriformis, which was previously shown to feed on bacteria, particularly under low concentrations of dissolved inorganic nutrients. Given its mixotrophic proclivities and phylogenetic position, N. pyriformis has the potential to provide insights into early green algal evolution and ecophysiology. In this study, we have presented a highly contiguous nuclear genome assembly for N. pyriformis. We acquired both Illumina and PacBio long-read data to assemble a 70.8-Mbp nuclear genome annotated with a total of 19,330 protein-coding genes. The genome is inferred to be haploid based on the base frequency distribution at variable sites, together with prior cell biological information from a related species. When compared with four other green algal genomes, N. pyriformis displayed a relatively large proportion of ortholog genes shared with the Chlorophyta. The nuclear genomic data presented here will be valuable for a range of studies, including green algal phylogenomics, genome evolution, and phago-mixotrophy.