Haslea silbo, A Novel Cosmopolitan Species of Blue Diatoms

Abstract

Specimens of a new species of blue diatoms from the genus Haslea Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, Haslea silbo sp. nov. A preliminary characterization of its blue pigment shows similarities to marennine produced by Haslea ostrearia, as evidenced by UV–visible spectrophotometry and Raman spectrometry. Life cycle stages including auxosporulation were also observed, providing data on the cardinal points of this species. For the two most geographically distant populations (North Carolina and East Mediterranean), complete mitochondrial and plastid genomes were sequenced. The mitogenomes of both strains share a rare atp6 pseudogene, but the number, nature, and positions of the group II introns inside its cox1 gene differ between the two populations. There are also two pairs of genes fused in single ORFs. The plastid genomes are characterized by large regions of recombination with plasmid DNA, which are in both cases located between the ycf35 and psbA genes, but whose content differs between the strains. The two sequenced strains hosts three plasmids coding for putative serine recombinase protein whose sequences are compared, and four out of six of these plasmids were highly conserved.

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

“…The two putative serC genes are intact and not pseudogenes [18].The genome contains a single intron, a group II intron in psaA with a 515 amino-acid long ORF coding for a putative reverse transcriptase. Similar introns in the same gene have been previously identified in various microalgae such as the diatoms Toxarium undulatum Bailey 1854 (AOS86555) [16] and Haslea silbo Gastineau, Hansen and Mouget 2021 (QUS63628 and QUS63831) [19], the silicoflagellate Dictyocha speculum Ehrenberg 1839 (QDH81707) [20], the red alga Bulboplastis apyrenoidosa A.Kushibiki, A.Yokoyama, M.Iwataki, J.Yokoyama, J.A.West & Y.Hara 2012 (ARO90857) [21], and the green alga Chlamydomonas applanata Pringsheim 1930 (ALO63257) [22]. The best blastp hit (62.02% identity and E-value = 0.0) was obtained with the D. speculum intron-encoded protein.…”

“…Although change in IR length is generally the major source of plastid genome size variation among diatoms, gains of sequences through horizontal transfers or recombination with plasmids sometimes contribute to larger genome size. This is the case for the 156,157 bp cpDNA of H. silbo that acquired a sequence of about 30 kb in the LSC region through recombination with plasmids [19].…”

Mitochondrial and Plastid Genomes of the Monoraphid Diatom Schizostauron trachyderma

“…In contrast, for example, to the Haslea silbo Gastineau, Hansen, and Mouget plastid genome that recently revealed all serC and xerC sequences in a single ca. 30 kb fragment located between ycf35 and psbA [ 26 ], these elements are located in five distinct regions of the S. trachyderma (between the IR and psaJ , ycf90 and psbZ , psbB and rbcS , atpA and rps14 , tsf and atpB ).…”

Nitzschia anatoliensis sp. nov., a cryptic diatom species from the highly alkaline Van Lake (Turkey)

“…Danielidis & D.G. Mann ( Brembu et al 2014 ) or with Haslea silbo Gastineau, Hansen and Mouget ( Gastineau et al 2021b ). Genes are encoded on both strands.…”

“…The valve ultrastructure was characterized by means of light and scanning electron microscopy. In the frame of the current effort of genomic characterization of populations and species of diatoms (see Prasetiya et al, 2019 ; Gastineau et al, 2021a , 2021b ), the complete organellar genomes of N. anatoliensis were sequenced, they were used for molecular phylogenies and compared with organellar genomes from related species.…”