Fottea 9(2): 169–177, 2009 169 Pseudomarvania, gen. nov. (Chlorophyta, Trebouxiophyceae), a new genus for “budding” subaerial green algae Marvania aerophytica NEUSTUPA et ŠEJ N OHOVÁ and Stichococcus ampulliformis HA N DA Marek EL I Á š & Jiří NE USTUPA * Charles University in Prague, Faculty of Science, Department of Botany, Benátská 2, CZ–128 01 Praha 2, Czech Republic; *corresponding author e–mail: [email protected] Abstract: Several unicellular green algae exhibit a unique type of cell division, which can be likened to budding. These algae comprise Spongiochrysis hawaiiensis in Cladophorales (Ulvophyceae) and Stichococcus ampulliformis and species of the genus Marvania in the class Trebouxiophyceae. We determined the 18S rRNA gene sequence from Marvania aerophytica NE USTUPA et šE J N OHOVÁ and inferred its phylogenetic position. Our analyses demonstrated that M. aerophytica is unrelated to other species of the genus Marvania (including the type species M. geminata), but together with S. ampulliformis forms a lineage within a broader clade comprising also species of the order Prasiolales, Desmococcus spp., Gloeotilla spp., and non-monophyletic Stichococcus spp. We discuss morphological characteristics of M. aerophytica and S. ampulliformis and based on our results, we propose M. aerophytica and S. ampulliformis be reclassified into a newly established genus of “budding” green algae, Pseudomarvania, as Pseudomarvania aerophytica, comb. nov. and Pseudomarvania ampulliformis, comb. nov. Key words: evolution, Marvania, Stichococcus, phylogeny, Trebouxiophyceae, 18S rRNA Introduction considered to represent Nannochloris coccoides NAUMA nn , and both taxa belong to a clade Green algae exhibit a great diversity in the roughly corresponding to the traditional order patterns of cell division (PICK E TT –HE APS 1975). Chlorellales. Based on this finding and given the An interesting form of cell reproduction was light microscopical observations of YAMAMOTO et described by HI N DÁK (1976) in a freshwater al. (2003) indicating that the strain CCAP 251/1b planktonic unicellular green alga described is morphologically very similar to M. geminata, as Marvania geminata. Vegetative cells of M. Hen L E Y and colleagues reclassified N. coccoides geminata are spherical, but upon initiation of the as Marvania coccoides. However, as pointed out reproductive process the cell starts bulging until by TSCH er MAK –WO E SS (1999) and YAMAMOTO et the mother cell wall ruptures at the growing pole. al. (2007), the strain CCAP 251/1b does not fit The “bud” keeps expanding and when it reaches with the original description of the species N. the dimensions of the part of the cell retained in coccoides by NAUMA nn , hence the identity of the the remnant of the mother cell wall, two separate species M. ”coccoides” is uncertain. cells are formed. Ultrastructural investigations Stichococcus ampulliformis, described by HA N DA of dividing M. geminata cells revealed that et al. (2003) from a tree bark in Japan, extended the “budding” is a highly modified form of the occurrence of the budding–like cytokinesis in autosporulation (RE YMO N D et al. 1986, SLUIMA N & green algae beyond the genus Marvania. This alga RE YMO N D 1987, YAMAMOTO et al. 2007) designated occasionally forms short moniliform filaments, but as semi-exogenous autosporogenesis (SLUIMA N & otherwise is quite unlike typical representatives of RE YMO N D 1987). the genus Stichococcus. Electron microscopical The phylogenetic position of M. geminata investigations revealed that the “budding” is also was first illuminated by Hen L E Y et al. (2004) a modified autosporulation with two autospores with the use of 18S rRNA gene sequences. This of highly unequal size formed within the mother study showed that M. geminata is very closely cell wall. A phylogenetic analysis based on a related to a strain (CCAP 251/1b) previously partial 18S rRNA gene sequence indicated that 170 EL I Á š & NE USTUPA : Pseudomarvania, gen. nov. S. ampulliformis is indeed related to Stichococcus Materials and methods species within the class Trebouxiophyceae, but the Stichococcus genus appeared paraphyletic The cells of the CAUP H 7301 strain of Marvania owing to sequences from Prasiola spp. disrupting aerophytica were cultured in agar–solidified BBM. its monophyly (HA N DA et al. 2003). Regardless For details of cultivation see NE USTUPA & šE J N OHOVÁ the uncertainties about the precise relationship of (2003). The cells were photographed using the Olympus S. ampulliformis to other Stichococcus species, it BX51 light microscope and the Olympus Z5060 digital equipment using Nomarski differential contrast after is clear that S. ampulliformis is not closely related 10 weeks of cultivation. to the genus Marvania. For isolation of genomic DNA, cells were scraped Additional “budding” green alga, from an agar plate with a clean spatula, transferred into Spongiochrysis hawaiiensis, has recently an Eppendorf tube, resuspended in distilled water and been described from a terrestrial habitat on harvested by centrifugation. Total DNA was extracted Hawaii, U.S.A. (RI N DI et al. 2006). Analyses using the Invisorb® Spin Plant Mini Kit (Invitek). of 18S rRNA gene sequences revealed that S. The sequence of the 18S rRNA gene was determined hawaiiensis belongs to the order Cladophorales by sequencing of two overlapping segments obtained in the class Ulvophyceae, and is thus even more by PCR amplification of the genomic DNA. The first distantly related to the genus Marvania than S. segment was amplified by using the unpublished forward primer 34F and the reverse primer 1650Rmod, ampulliformis. All these results indicate that the whose sequences were kindly shared with us by Prof. budding-like form of cell division has evolved Thomas Friedl, University of Göttingen. The second at least several times in the course of green algal segment was amplified using the forward primer phylogeny. It follows that “budding” of particular 1500af (HE LMS et al. 2001) and the reverse primer ITS4 green algal species does not qualify them a priori (WHIT E et al. 1990). The PCR products were purified as close relatives and other features, especially using the JETQUICK PCR Product Purification Spin molecular characters, must be taken into account Kit (Genomed). The first segment was sequenced when a phylogenetic position of such species is to from both ends using the amplification primers and be determined. internal sequencing primers from KATA N A et al. (2001). One species, on whose taxonomic and The second segment was sequenced with the 1500af primer and the 18S rRNA R primer from KATA N A et phylogenetic status was judged solely on the al. (2001). Sequencing reactions were performed basis of the budding–like cytokinesis and in the using the BigDye Terminator v3.1 Cycle Sequencing absence of molecular data, was described from a Kit (Applied Biosystems) and analysed with the 3130 subaerial habitat in tropical Malaysia (NE USTUPA Genetic Analyzer (Applied Biosystems). Sequencing & šE J N OHOVÁ 2003). Since the genus Marvania reads were assembled with the CAP3 assembler was the only “budding” green algal taxon known server (http://pbil.univ-lyon1.fr/cap3.php), and the at that time, the species was attributed to this assembly was manually edited by visual inspection of genus as a new species, Marvania aerophytica. sequencing chromatograms. The assembled sequence The taxonomic descriptions of M. aerophytica and contains a gap in a region corresponding to an S934 S. ampulliformis were published independently at intron, because the intron appears to be very long and the primers employed for sequencing did not allow essentially the same time. RI N DI et al. (2006) noted reading through the whole intron. The 3’ end of the the morphological similarity of M. aerophytica sequence stops within an S1506 intron (we did not and S. ampulliformis and suggested that these attempt to extend the sequence further downstream, two algae might be conspecific. To resolve the because it would not provide any information relevant taxonomic identity and phylogenetic position with respect of the aims of this study). The newly of M. aerophytica, we sequenced the 18S rRNA obtained 18S rDNA sequence of M. aerophytica CAUP gene from the type strain and conducted a series H 7301 was deposited in GenBank with the accession of phylogenetic analyses. The results indicate that number FJ896222. M. aerophytica and S. ampulliformis are distinct, Construction of multiple alignments including the yet related, species, which should be treated as newly determined 18S rDNA sequence and the strategy a genus separate from other trebouxiophycean used to select representative sequences for a broader genera described so far. phylogenetic analysis to determine the position of M. aerophytica were done as described previously (NE USTUPA et al. 2009). In addition, we prepared a second alignment comprising wide selection of sequences from the Stichococcus/Prasiola clade (see text and Fig. 3). For this analysis we omitted some highly similar Fottea 9(2): 169–177, 2009 171 sequences from the genera Prasiola and Rosenvingiella and one of the redundant sequences (EU434026.1) for Desmococcus endolithicus SAG 25.92, but otherwise we included all sequences from this clade available as of February 2009. Sequences from Coenocystis inconstans, Chlorella mirabilis Andreyeva 748–I, and representatives of the Raphidonema/Pseudochlorella clade were used as the outgroup for the Stichococcus/ Prasiola clade, following the results of the broader analysis. Maximum likelihood (ML) tree inferences were carried out with PhyML 3.0 (GUI N DO N & GASCU E L 2003) operated at the ATGC bioinformatics platform (http://www.atgc-montpellier.fr/phyml/), employing the GTR+F+I+Γ8 substitution model and the SRN & NNI heuristics. ML bootstrap support was calculated from 100 bootstrap replicates. Evaluation of the tree topologies was also performed with the neighbour joining (NJ) method as implemented in the PHYLIP 3.6 package (FE LS en ST E I N 2004). 1000 bootstrap replicates of the alignments were created with the seqboot Fig.