Evans J.R., St. Amour N., Verbruggen H., Salomaki E.D. & Vis M.L.
Content and architecture of organellar genomes in the freshwater red algal epiphyte Balbiania investiens (Balbianiales, Nemaliophycidae)
Journal of Phycology: submitted


The small but diverse red algal subclass Nemaliophycidae contains eleven orders with three restricted to freshwater environments. Recent studies have reported organellar genomes for five of the orders and have demonstrated their utility for phylogenomics and genome evolution. Of the three strictly freshwater orders, only the Balbianiales lacks organellar genome data. To this end, we performed high-throughput, paired-end sequencing to assemble and annotate the plastid and mitochondrial genomes of Balbiania investiens (culture collections SAG15.96, SAG50.93), an epiphyte of batrachospermalean taxa in European streams. The newly sequenced B. investiens organellar genomes were compared to those available for the Nemaliophycidae and select florideophytes. The 186,778 bp plastid genome encodes 199 protein-coding genes, 6 rRNAs, 33 tRNAs, 1 ncRNA, and 1 tmRNA. Notable losses from the plastid include genes involved with the LIPOR enzyme, highly conserved group II introns, and an allophycocyanin subunit (apcF). Balbiania investiens encodes the pbsA gene for heme oxygenase, and it is the only sequenced freshwater plastid genome to encode a glutaredoxin (grx). Architecturally, the plastid genome is most like the marine orders Acrochaetiales and Palmariales. The mitochondrial genome is 26,389 bp and encodes 25 protein-coding genes, 2 rRNAs, and 23 tRNAs. There are only slight differences in genome content and architecture among B. investiens and other mitochondrial genomes in the subclass. This study provides genomic data for a sixth order in the Nemaliophycidae and contributes to a collaborative dataset that will be imperative for future phylogenomic investigations and studies of organellar genome evolution.

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