Extreme Enlargement of the Inverted Repeat Region in the Plastid Genomes of Diatoms from the Genus Climaconeis

We sequenced the plastid genomes of three diatoms from the genus Climaconeis, including two strains formerly designated as Climaconeis scalaris. At 208,097 and 216,580 bp, the plastid genomes of the latter strains are the largest ever sequenced among diatoms and their increased size is explained by the massive expansion of the inverted repeat region. Important rearrangements of gene order were identified among the two populations of Climaconeis cf. scalaris. The other sequenced Climaconeis chloroplast genome is 1.5 times smaller compared with those of the Climaconeis cf. scalaris strains and it features an usual quadripartite structure. The extensive structural changes reported here for the genus Climaconeis are compared with those previously observed for other algae and plants displaying large plastid genomes.

Automated summary

In this study, the plastid genomes of three diatoms from the genus Climaconeis were sequenced, with two strains of Climaconeis scalaris having the largest genomes ever sequenced among diatoms. Significant rearrangements of gene order were identified in the two populations of Climaconeis cf. scalaris. Another sequenced Climaconeis chloroplast genome was 1.5 times smaller than those of the Climaconeis cf. scalaris strains and had a different quadripartite structure. Extensive structural changes in the Climaconeis genus were compared with those seen in other algae and plants with large plastid genomes.