The austral biflagellate Chloromonas rubroleosa (Chlorophyceae) is the closest relative of the unusual quadriflagellate genus Chlainomonas, both found in snow

Abstract

The quadriflagellate genus Chlainomonas frequently dominates red snow globally. It is unusual in several respects, with two separated pairs of flagella, apparent cell division via extrusion of cytoplasmic threads, and being nested phylogenetically within the biflagellate genus Chloromonas. Here, we showed that the austral species Chloromonas (Cr.) rubroleosa, originally described from Antarctic red snow, is a close biflagellate relative of Chlainomonas, challenging the monophyly of Chlainomonas as currently conceived. Sequences of the 18S rRNA gene robustly linked Cr. rubroleosa with near-identical environmental sequences from Antarctic red snow and Chlainomonas from North America, Japan, and Europe. Furthermore, the 18S rRNA and rbcL gene sequences of Cr. rubroleosa were almost identical to New Zealand and North American collections of Chlainomonas. Cr. rubroleosa and New Zealand Chlainomonas are separated by only a single-base substitution across the ITS1-5.8S-ITS2 rRNA loci (and according to ITS2, the North American collection is the next closest relative). This again raises the possibility that Chlainomonas is a life-cycle stage of vegetatively biflagellate organisms, although this remains confounded by the scarcity of biflagellates in field populations, the apparent cell division by quadriflagellates, and the absence of Chlainomonas-type cells in cultures of Cr. rubroleosa. The latter species is broadly similar to Chlainomonas, being poor at swimming, with similar pigment, chloroplast arrangement and ultrastructure, and is relatively large. Increased size is a feature of the wider clade of "Group D" snow algae. A synthesis of field and laboratory investigations may be needed to unravel the life cycle and correct the systematics of this group.

Rosetta gen. nov. (Chlorophyta): Resolving the identity of red snow algal rosettes

“…(2018), who placed Star‐like morphologies from Alaska in Chloromonadinia (Figure 6). Our data are consistent with previous studies, successfully reproducing Chloromonas groups A, B, and C, where A and C are sister clades (Matsuzaki et al., 2015, 2018, 2019; Nakashima et al., 2021; Novis et al., 2023; Procházková, Remias, et al., 2019). Based on robust molecular phylogeny and microscopic characterization, we designate five novel species belonging to a novel genus Rosetta .…”

“…Rosetta , along with Chlainomonas , Gloeomonas , and Ixipapillifera , were all originally included within Chloromonas , which is paraphyletic and no longer stands as a genus (Barcytė et al., 2018; Novis et al., 2023; Nozaki et al., 2010; Pröschold et al., 2001). We note that the genus Chloromonas is still used in reference to a small clade including C. reticulata (Barcytė et al., 2020).…”

“…Sanguina and Chloromonadinia sequences were downloaded from GenBank for inclusion in phylogenetic trees (Barcytė et al, 2018;Lewis & Lewis, 2005;Leya, 2004;Matsuzaki et al, 2014Matsuzaki et al, , 2015Matsuzaki et al, , 2018Matsuzaki et al, , 2019Morita et al, 1999;Muramoto et al, 2010;Novakovskaya et al, 2018;Novis et al, 2008Novis et al, , 2023Procházková, Leya, et al, 2019;Procházková, Remias, et al, 2019;Procházková, Remias, Holzinger, et al, 2018;Procházková, Remias, Rezanka, et al, 2018;Pröschold et al, 2001;Raymond et al, 2022;Remias et al, 2010Remias et al, , 2013Remias et al, , 2018Segawa et al, 2018). Single-cell and reference sequences were aligned using the DECIPHER library in R v4.2 (R Core Team, 2020; Wright, 2016), visually checking all alignments to ensure that the majority of nucleotides were conserved across samples.…”

Patchy and Pink: Dynamics of a Chlainomonas sp. (Chlamydomonadales, chlorophyta) algal bloom on Bagley Lake, North Cascades, WA

“…3A – F . The Chlainomonas species that dominates Upper Bagley Lake is a new species and is larger than Chlainomonas rubra , though it nests within other sequences identified as C. rubra (Novis et al 2023 , Matsumoto et al in review). Chlainomonas sp.…”

“…We have observed this pattern of early blooms on the lake, which are dominated by Chlainomonas sp., every year since 2017. This species is an undescribed species of Chlainomonas (Novis et al 2023 , Matsumoto et al in review). This species represents over 98% of amplicons from lake samples from 2017 to 2019 (R. Kodner, unpublished data) and in all microscopy samples collected from 2017 to 2023 (R. Kodner, unpublished data).…”