Mitochondrial and plastid genome variability of Corallina officinalis (Corallinales, Rhodophyta)

Corallina officinalis is a calcifying red alga, common in tide pools in the North Atlantic with occasional reports from the north-east Pacific. It is an important habitat-forming alga, providing shelter and substrata to many other organisms. To date there are only five published organellar genomes for Corallina, including C. chilensis and C. ferreyrae. This study reports the first four published plastid genomes for C. officinalis, along with three new mitogenomes from samples in the United Kingdom, Spain and Iceland. The plastid genome is 178 kbp and 99.9% of bases are identical for all samples. The mitogenomes are more variable than the plastid genomes, with lengths varying from 26.2 to 26.7 kbp and 99.0% base identity. Structure and length of both of the genomes are consistent with other published Corallina genomes. The most variable mitochondrial gene is sdhD (3.3% variability), while all plastid genes have <1% base variability, with the most variable being psb30 (0.95% variability). The stability of the plastid genome means it is not useful for examining intra-specific variability within Corallina. We discuss whether the ratio of mitogenome and plastome sequences recovered in the readpool of NGS sequencing is indicative of relative copy number.