Chloroplast and mitochondrial genomes of Balbiania investiens (Balbianiales, Nemaliophycidae)

Abstract

ABSTRACTThe Balbianiales is one of only three strictly freshwater orders in the red algal subclass Nemaliophycidae. To date, organellar genomes for one of the 11 orders have been reported, including the other two strictly freshwater orders. There are no organellar genome data from Balbianiales and these data will better enable evolutionary studies of red algal plastids. We performed high-throughput sequencing to assemble and annotate organellar genomes of Balbiania investiens. The 186,778 bp plastid genome encodes 199 protein-coding genes, six rRNAs, 33 tRNAs, one ncRNA, and one tmRNA. Notable losses from the plastid genome included genes involved with the LIPOR enzyme, highly conserved group II introns, and apcF. Balbiania investiens has two protein-coding genes in its plastid genome that are not consistently annotated in the other sequenced freshwater genomes of the subclass. The pbsA gene is reported only in B. investiens and in one member of the Batrachospermales (Sheathia arcuata), and grx is reported only in B. investiens. 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, two rRNAs, and 23 tRNAs. There were only slight differences in genome content and architecture between B. investiens and other mitochondrial genomes in the subclass. This study provides genome data for a sixth Nemaliophycidae order, identifies potential issues in the assembly of inverted repeat regions and the annotation of genes with multiple accepted names, and contributes to a growing dataset for phylogenomic and organellar genome evolution investigations.