Valve morphogenesis in selected centric diatoms

The traditional taxonomic affiliation of the diatom Ardissonea crystallina (C. Agardh) Grunow has been recently questioned, as it exhibits a mixture of polar centric and araphid pennate characters. Overall valve architecture and mode of sexual reproduction suggest that araphid pennates are its closest relatives. On the other hand, recovered molecular phylogenies consistently place it among the polar centrics. Our investigation of the earliest stages of valve morphogenesis, formation of the basal silica layer, adds to the argument that A. crystallina is indeed a polar centric diatom. We compared developmental stages in A. crystallina with unequivocally centric diatoms (non-polar Hyalodiscus stelliger and polar Biddulphia tridens) and published literature for araphid pennates and determined that A. crystallina has evolved an apparently unique mode of valve development. The significance of valve morphogenesis in better understanding diatom evolution and diversification is discussed.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

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