Volvox reticuliferus NIES-3786 asexual and sexual male spheroids. Image credit: Hisayoshi Nozaki.

V. reticuliferus NIES-3786 asexual spheroid with daughter spheroids. Image credit: Hisayoshi Nozaki.

Male spheroid showing sperm packets (bundles of male gametes). Image credit: Hisayoshi Nozaki.

The Volvox reticuliferus NIES-3786 genome sequence and gene models were not determined by the Joint Genome Institute (JGI), but were downloaded from NCBI on March 6, 2023. All published models are available as ExternalModels. In order to ensure this genome is comparable to those sequenced annotated by the JGI , we applied standard filters to ExternalModels to produce the initial GeneCatalog. A total of 8,380 of 21,354 external models were excluded based on one of the following classifications: 1) association with repetitive elements, 2) pseudogenes with internal stop codons, 3) alternative isoforms or overlapping transcript models, 4) alleles on secondary/smaller scaffolds, and 5) short models lacking functional annotation. Please note that this copy of the genome is not maintained by NCBI and is therefore not automatically updated. In order to allow comparative analyses with other algal genomes sequenced by the JGI, a copy of this genome is incorporated into PhycoCosm. The JGI Annotation Pipeline was used to add functional annotation to the genes.

Volvox reticuliferus NIES-3786

Volvox reticuliferus is a freshwater chlorophyte alga producing asexual and sexual multicellular spheroids. Asexual spheroids are haploid and reproduce by formation of daughter spheroids. Sexual reproduction of V. reticuliferus is heterothallic with male and female genotypes that produce male and female gametes (sperm and eggs, respectively) in sexual male and female spheroids, respectively (heterothallism). V. reticuliferus strain NIES-3785 is female whereas NIES-3786 is male. V. reticuliferus was previously identified as a heterothallic subgroup within "V. africanus" (Nozaki et al. 2015). A comparative genomic study between heterothallic V. reticuliferus and homothallic V. africanus provided exciting insights into the evolution of sex chromosomes in haploid organisms (Yamamoto et al. 2021). Further comparative studies of these two species promises deeper insights into evolution and diversity of sex chromosomes in eukaryotes.