Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2006 Feb 13;6:2.
doi: 10.1186/1471-2229-6-2.

EST Analysis of the Scaly Green Flagellate Mesostigma Viride (Streptophyta): Implications for the Evolution of Green Plants (Viridiplantae)

Affiliations
Free PMC article

EST Analysis of the Scaly Green Flagellate Mesostigma Viride (Streptophyta): Implications for the Evolution of Green Plants (Viridiplantae)

Andreas Simon et al. BMC Plant Biol. .
Free PMC article

Abstract

Background: The Viridiplantae (land plants and green algae) consist of two monophyletic lineages, the Chlorophyta and the Streptophyta. The Streptophyta include all embryophytes and a small but diverse group of freshwater algae traditionally known as the Charophyceae (e.g. Charales, Coleochaete and the Zygnematales). The only flagellate currently included in the Streptophyta is Mesostigma viride Lauterborn. To gain insight into the genome evolution in streptophytes, we have sequenced 10,395 ESTs from Mesostigma representing 3,300 independent contigs and compared the ESTs of Mesostigma with available plant genomes (Arabidopsis, Oryza, Chlamydomonas), with ESTs from the bryophyte Physcomitrella, the genome of the rhodophyte Cyanidioschyzon, the ESTs from the rhodophyte Porphyra, and the genome of the diatom Thalassiosira.

Results: The number of expressed genes shared by Mesostigma with the embryophytes (90.3 % of the expressed genes showing similarity to known proteins) is higher than with Chlamydomonas (76.1 %). In general, cytosolic metabolic pathways, and proteins involved in vesicular transport, transcription, regulation, DNA-structure and replication, cell cycle control, and RNA-metabolism are more conserved between Mesostigma and the embryophytes than between Mesostigma and Chlamydomonas. However, plastidic and mitochondrial metabolic pathways, cytoskeletal proteins and proteins involved in protein folding are more conserved between Mesostigma and Chlamydomonas than between Mesostigma and the embryophytes.

Conclusion: Our EST-analysis of Mesostigma supports the notion that this organism should be a suitable unicellular model for the last flagellate common ancestor of the streptophytes. Mesostigma shares more genes with the embryophytes than with the chlorophyte Chlamydomonas reinhardtii, although both organisms are flagellate unicells. Thus, it seems likely that several major physiological changes (e.g. in the regulation of photosynthesis and photorespiration) took place early during the evolution of streptophytes, i.e. before the transition to land.

Figures

Figure 1
Figure 1
Classification of expressed genes from Mesostigma according to the presence of similar proteins in other organisms in a Venn diagram. All non-redundant expressed genes were used as a query in (t)blastx similarity searches with the Swissprot, Genbank, Chlamydomonas, Cyanidioschyzon, Porphyra, Physcomitrella, Arabidopsis and Oryza data sets. The outermost circle represents all Mesostigma expressed genes. The inner circles, which are labeled chlorophyte, streptophyte and rhodophyte, represent genes, which have similarity to chlorophyte, streptophyte or rhodophyte sequences, respectively. The areas depicted are not proportional to the gene numbers and the number of Mesostigma expressed genes in each category is written in each segment. Numbers in brackets indicate the number of expressed genes in a category after removal of low similarity hits (see Table 2 for a definition of low similarity hits).
Figure 2
Figure 2
Consistency of the constrained data set used to calculate AI values. (A) The figure illustrates the effect of the number of genes included in the AI-values. The significant differences in the AI values are stable when more than 150 genes are included. (B) 150 genes were resampled randomly and the AIs calculated for the indicated organisms (1 – 8). AI values were calculated for the 150 most strongly (9, as revealed by the number of ESTs in a contig) and weakly (10, only single ESTs) expressed genes.
Figure 3
Figure 3
Alignment of the deduced amino acid sequence of the putative GAPDHB (Meso2a42g12) gene from Mesostigma with spinach (P12860) GAPDHB. The conserved cysteine residues are indicated in red letters. Numbers refer to the amino acid position (spinach) or nucleotide position (Mesostigma).
Figure 4
Figure 4
Phylogenetic tree of glycolate oxidase and glycolate oxidase-like genes. The tree shown was derived by Bayesian inference analysis from 402 amino acid positions using a mixed model for amino acid substitutions and a gamma correction for rate variation among sites. The Bayesian inference utilized MRBAYES, Ver. 3.0 * with posterior probabilities derived from 100000 generations and discarding a burnin of 1000. The tree obtained with a parsimony analysis using PHYLIP gave essentially the same topology.

Similar articles

See all similar articles

Cited by 12 articles

See all "Cited by" articles

References

    1. Sanderson MJ, Thorne JL, Wikstrom N, Bremer K. Molecular evidence on plant divergence times. Am J Bot. 2004;91:1656–1665. - PubMed
    1. Bateman RM, Crane PR, DiMichele WA, Kenrick PR, Rowe NP, Speck T, Stein WE. Early evolution of land plants: Phylogeny, physiology, and ecology of the primary terrestrial radiation. Annu Rev Ecol Syst. 1998;29:263–292. doi: 10.1146/annurev.ecolsys.29.1.263. - DOI
    1. Kenrick P, Crane PR. The origin and early diversification of land plants. Washington, London: Smithsonian Institution Press; 1997.
    1. Graham LE. Origin of Land Plants. New York: John Wiley & Sons, Inc; 1993.
    1. Waters ER. Molecular adaptation and the origin of land plants. Molecular Phylogenetics and Evolution. 2003;29:456–463. doi: 10.1016/j.ympev.2003.07.018. - DOI - PubMed

Publication types

Associated data