A unique, highly variable mitochondrial gene with coding capacity of Heterosigma akashiwo, class Raphidophyceae

Phylogeographic characteristics of hypervariable regions in the mitochondrial genome of a cosmopolitan, bloom‐forming raphidophyte, Heterosigma akashiwo

“…We identified MtORFvar1 (previously termed MtORFvar ) as a hypervariable protein coding sequence in the Heterosigma akashiwo mtDNA whole genome of seven strains originating in North America and Japan in our previous study (Higashi et al. ,b). Here, we identify two additional hypervariable segments, MtORFvar2 and IGRvar, by systematically comparing the whole mtDNAs of 15 H. akashiwo strains obtained from east and west sides of Pacific and Atlantic oceans from northern hemisphere, and South Pacific Ocean (New Zealand) and South Atlantic Ocean (Brazil).…”

“…Our previous study based on the MtORFvar1 sequences of 17 strains originating in the northern hemisphere, classified the sequences into four distinct groups consisting of strains from high‐latitude Pacific regions, high‐latitude Atlantic regions, low‐latitude eastern Pacific regions, and others: Significant isolation‐by‐distance was also observed based on the analyses (Higashi et al. ,b). In the present study, we analyzed total 27 strains, including 7 strains originating in the Southern Hemisphere (New Zealand and Brazil), 1 from Singapore (approximately on the equator), and 10 strains from ≥41.4° and 9 from other regions of the Northern Hemisphere.…”

“…The cells were harvested and stored at −80°C until the DNA extraction as described previously (Higashi et al. 2017a).…”

“…Previously, we identified a mitochondrial gene ( MtORFvar ) that exhibits prominent sequence variation associated with the geographic origin of the strain (Higashi et al. ,b). In the course of further exploration of the mitochondrial genome (mtDNA) as a device for phylogeographic study, we identified two additional variable segments in Heterosigma akashiwo mtDNA.…”

Chloroplast Genome Sequences of Seven Strains of the Bloom-Forming Raphidophyte Heterosigma akashiwo

“…Establishing strain markers will allow the monitoring of geographical and temporal dynamics of the species. We previously sequenced whole-mitochondrial genomes of four strains of this species and identified a hypervariable protein-coding sequence associated with the geographic origins of the strains (13–15). …”