“The genus this website Peridinium Ehrenb. comprises a group of highly diversified dinoflagellates. Their morphological taxonomy has been established over the last century. Here, we examined relationships within the genus Peridinium, including Peridinium bipes F. Stein sensu lato, based on a molecular phylogeny derived from nuclear rDNA sequences. Extensive rDNA analyses of nine selected Peridinium species showed that intraspecies genetic variation was considerably low, but interspecies genetic divergence was high (>1.5% dissimilarity
in the nearly complete 18S sequence; >4.4% in the 28S rDNA D1/D2). The 18S and 28S rDNA Bayesian tree topologies showed that Peridinium species grouped according to their taxonomic positions and certain morphological characters (e.g., epithecal plate formula). Of these groups, the quinquecorne group (plate formula of 3′, 2a, 7″) diverged first, followed by the umbonatum group (4′, 2a, 7″) and polonicum
group (4′, 1a, 7″). Peridinium species with a plate formula of 4′, 3a, 7″ diverged last. Thus, 18S and 28S rDNA D1/D2 sequences are informative about relationships among Peridinium species. Statistical analyses check details revealed that the 28S rDNA D1/D2 region had a significantly higher genetic divergence than the 18S rDNA region, suggesting that the former as DNA markers may be more suitable for sequence-based delimitation of Peridinium. The rDNA sequences had sufficient discriminative power to separate P. bipes f. occultaum (Er. Lindem.) M. Lefèvre and P. bipes f. globosum Er. Lindem. into two distinct species, even though these taxa are morphologically only marginally discriminated by spines on antapical GBA3 plates and the shape of red bodies during the generation of cysts. Our results suggest that 28S rDNA can be used for all Peridinium species to make species-level taxonomic distinctions, allowing improved taxonomic classification of Peridinium. “
“The collagen protein family is diverse and its membership is continually expanding as new collagen-like molecules are identified.
Identification of collagen in unicellular eukaryotes and prokaryotes has opened discussion on the function of these collagens and their role in the emergence of multicellularity. The previous identification of a collagen gene in Trichodesmium erythraeum raises the question of function of this structural protein in a prokaryote. In this study, we show that this gene is expressed during all phases of growth, indicating that it may be required for all phases of growth. Using immunofluorescence techniques, we demonstrate that the collagen-like protein is localized in a specific manner between adjacent cells along the trichome of T. erythraeum. Trichomes treated with the enzyme collagenase exhibited fragmentation, supporting our immunofluorescence localization data that this collagen-like protein is found between adjacent cells.