For example, species of Closterium provide excellent models for studying reproductive biology. In this series, Abe et al. The stoneworts e. These algae produce exceptionally large internodal cells that are uniquely valuable to various cellular studies. Belby describes the distinct features of these algae and specifically reports on the diverse methodologies that have been used and key results that have been obtained in studies dealing with electrophysiology, auxin dynamics and membrane transporters.
Central to the physiology of any plant cell including Chara is endomembrane dynamics especially the coordinated balance between exo- and endocytosis in the membrane trafficking network.
Foissner et al. Using immunofluorescence and transmission electron microscopy-based imaging they demonstrate significant reorganization of the trans Golgi network TGN and changes to the unique membranous charasomes. Ultimately, the expansion and development of the cells of Chara , as in all plants, is controlled by turgor and the structural dynamics of the cell wall.
Pectins represent the largest domain of the wall matrix polysaccharides that are critical to cell development. Overview Articles Authors Impact. About this Research Topic The charophytes Streptophyta,Virideplantae are the extant group of green algae that are most closely related to modern land plants.
Topic Editors. Views Demographics No records found total views article views article downloads topic views. A MrBayes consensus tree is shown, where the posterior probabilities are displayed as percent values. GapA sequences were established from all other species analyzed in this study P. However, exhaustive efforts to identify GapB from mosses Physcomitrella , Sphagnum were unsuccessful.
In accordance with our phylogenetic analyses see below , the most probable explanation for this absence is a secondary loss of GapB genes in mosses; the same argument might also apply for the charophyte Klebsormidium. All reference sequences were retrieved from the databases Supplementary Table S1, Supplementary Material online , and the deduced amino acid sequences were used for alignments and phylogenetic analyses.
Figure 1 shows a Bayesian consensus tree based on the phylogenetic analysis of 57 eukaryotic GapA and GapB sequences rooted with 16 cyanobacterial Gap2 outgroup sequences see also Supplementary Fig.
S1, Supplementary Material online. The data set comprises streptophyte sequences of various land plants including mosses Physcomitrella , Sphagnum and a liverwort Marchantia. Moreover, it contains representatives of all five charophycean orders Coleochaetales Coleochaete , Charales Chara , Zygnematales Spirogyra , Klebsormidiales Klebsormidium , and Chlorokybales Chlorokybus as well as the unicellular green flagellate Mesostigma Graham and Wilcox Several representatives of the Chlorophyta from the classes Chloro- Chlamydomonas , Spermatozopsis , Scenedesmus , Ulvo- Cladophora , Acetabularia , Trebouxio- Chlorella , and Prasinophyceae Scherffelia are also included.
The two remaining primary photosynthetic lineages are represented by sequences of Cyanophora Glaucophyta and five red algae Rhodophyta. Sequences established in this study are in boldface.
The horizontal length of the triangles is equivalent to the average branch length for complete tree, see Supplementary Fig. Mesostigma represents the first branching lineage in both subtrees followed by the charophytes.
This observation is corroborated by the GapB-specific sequence pattern including two insertions of one amino acid fig. However, a comparison of the average branch length of the respective subtrees after this short phase of accelerated evolution reveals that GapB genes exhibit a remarkable degree of sequence conservation that is clearly higher than that of the respective GapA counterparts fig.
Specific signatures in GapB and GapA amino acid sequences from different land plants and green algae. GapB-specific insertions are shown as a negative image and GapB-specific sites are shaded in gray.
GapA and GapB sequences of the unicellular green alga Mesostigma congruently branch prior to charophytes, while Chlorokybus is the most basal charophyte in the slowly evolving GapB subtree. The position of Klebsormidium among bryophytes and seed plants within the GapA subtree obtains no significant statistical support; actually, phylogenetic analyses with reduced data sets indicate that this placement is the result of a long-branch attraction LBA artifact caused by fast-evolving seed plant sequences data not shown.
Low support from both GapA and GapB subtrees allows no certain prediction about the closest charophycean relative of land plants. Therefore, a complementary approach is applied to resolve these evolutionary relationships by identification of specific sequence signatures. The most parsimonious explanation for shared insertions, deletions, and conserved amino acid positions between different genes is a common ancestry.
We detected five GapB-specific positions in the alignment that may correlate with the evolutionary relationships fig. Their pattern is completely different between land plants and the green algae Mesostigma and Chlorokybus. In contrast, Spirogyra and Chara share three and four of these positions, respectively, whereas the pattern of Arabidopsis and Coleochaete are even identical.
The reliability of the unexpected affiliation of C. Based on the phylogenetic tree shown in figure 1 , we placed Cyanophora at all alternative positions within the tree and tested a total of topologies. A total of 26 of them can be excluded in a biological context because they place this glaucophyte either within green plants A2 or within cyanobacteria A6. Among the two remaining meaningful topologies, the best ML tree proposes a green affiliation A1 and the alternative tree shows the familiar basal placement as first-diverging photosynthetic lineage A5.
The RELL bootstrap support, which allows a relative weighting of all tested topologies and adds up to 1. Our phylogenetic analyses demonstrate that the GapA sequences from Cyanidioschyzon and Porphyra have by far the longest branches within the rhodophycean clade Supplementary Fig. Therefore, we removed these two sequences from the tree and performed a second series of AU tests with topologies Supplementary Table S1, Supplementary Material online; series B. The results are comparable with those of the first analysis, but the resampling estimated log-likelihood RELL bootstrap support for the best tree increases from 0.
The mature CP12 subunit of land plants, chlorophytes, and some cyanobacteria is composed of two domains, both containing two highly conserved cysteine residues with a regulatory function Supplementary Fig. S2, Supplementary Material online Wedel and Soll Nevertheless, all available CP12 sequences exhibit a highly conserved C-terminal domain including the characteristic cysteines fig.
This also applies for the composite alignment of CP12 and GapB indicated by a gray background in fig. Conserved amino acid positions are indicated by dots. Two highly conserved cysteine residues are accentuated in dark gray, while the conserved similar amino acid positions between CP12 and GapB are shown in light gray.
The newly recruited CTE fig. The mechanism was established in a common ancestor of present-day cyanobacteria Pohlmeyer et al. This extensive regulation in plants assures the metabolic flexibility of the plastid, which switches from the reductive Calvin cycle for CO 2 fixation during illumination to the OPPP for reduced nicotinamide adenine dinucleotide phosphate generation at night Schnarrenberger, Oeser, and Tolbert ; Schnarrenberger, Flechner, and Martin An incomplete or missing inhibition of the Calvin cycle would result in futile cycling and a waste of adenosine triphosphate, as recently demonstrated by a cyanobacterial knockout mutant of CP12 that shows a significantly reduced growth rate Tamoi et al.
It is interesting in this context that diatom plastids, which were recruited via secondary endosymbiosis from a red alga, lost their OPPP Michels, Wedel, and Kroth , probably due to the replacement of the plastid GapA by a nuclear-encoded GapCI that is not susceptible to thioredoxin-mediated regulation Liaud et al.
These examples document the importance of blocking the Calvin cycle at night in the presence of OPPP, but they give no convincing answer for the necessity of two regulatory complexes in land plants.
The simplest explanation is that the newly emerged HMM complex tightens this inactivation in the dark, but a more auspicious prediction would be a crucial function of the GapB-dependent complex for streptophycean metabolism. This promising explanation is compatible with the observation that plastid starch storage is restricted to green plants, whereas rhodophytes and glaucophytes accumulate their polysaccharides e.
Therefore, the functional gain of GapB at the base of streptophycean evolution could constitute a metabolic prerequisite for the development of heterotrophic storage tissues in terrestrial plants including those with agricultural relevance as potatoes or cereal grains. We present the first study of nuclear-encoded plastid GAPDH as well as CP12 sequences of all three primary photosynthetic lineages green plants, red algae, and glaucophytes figs. This implies two endosymbiotic gene transfers from the plastid to the host cell nucleus in a common ancestor of the present-day lineages.
Thus, GAPDH and CP12 data independently support the commonly accepted prediction that plastids of green plants Chlorophyta and Streptophyta , rhodophytes, and glaucophytes can be traced back to a single primary endosymbiosis with a cyanobacterium Bhattacharya and Medlin ; Douglas ; Delwiche ; Rodriguez-Ezpeleta et al.
The branching order of these three primary lineages is still unclear, but in particular the glaucophyte-specific peptidoglycan wall and carboxysomes are generally regarded as ancient cyanobacterial traits Pfanzagl et al. Accordingly, several molecular analyses of concatenated plastid genomes show a basal position of glaucophytes prior to green plants and red algae, albeit only with weak to moderate statistic support Martin et al. Our analyses of plastid GapA sequences surprisingly favor an alternative placement of Cyanophora with green plants and thus a basal branching of the rhodophytes fig.
However, the RELL bootstrap proportion clearly supports the sistergroup relationship of glaucophytes and green plants presented in figure 1 , especially after elimination of the two fast-evolving red algal sequences Supplementary Table S2, Supplementary Material online; RELL support of 0. Even though hidden paralogy or cryptic lateral gene transfer may confound single-gene phylogenies, the same grouping has been obtained in analyses of concatenated nuclear-encoded genes, albeit without significant support Nozaki et al.
The pattern of presence or absence of chlorophyll b, phycobilins, or flagella leads to contradictory deductions for the relationships of the three basal lingeages van den Hoek, Mann, and Jahns ; Tomitani et al. Interestingly, Raven argues that peptidoglycan and carboxysomes are functionally linked in glaucophytes and associated with an adaption to freshwater habitats. Furthermore, considering that this functional trait is shared with the cyanobacterial ancestor, its maintenance in glaucophytes does not justify a basal positioning of this group Raven We conclude that the proposed sistergroup relationship with green plants fig.
Nevertheless, additional molecular data and especially a better species sampling of red algae and glaucophytes will be required to unequivocally determine the branching order of the three primary lineages. Unique events in evolution are excellent cornerstones to clarify the relationship of present-day lineages reliably.
Thorough analyses of endosymbiotic gene transfers offer the chance to reconstruct very ancient interkingdom linkages Harper and Keeling ; Petersen et al. The GapB-specific C-terminal domain allows an unambiguous identification of the respective gene fig.
Here we present a broad survey of plastid GapA and GapB genes from green plants including 20 newly established sequences and document that Chlorophyta exclusively harbor GapA genes fig. Because GapB was found in the liverwort M. However, the identification of GapB sequences in nearly all major groups of charophytes fig. The comparison of several GapB-specific sequence positions reveals the presence of identical sequence signatures in Arabidopsis and Coleochaete fig.
However, unequivocal molecular data are required to support or reject the assumption that the differentiated morphology of stoneworts Charales van den Hoek, Mann, and Jahns actually reflects an advanced evolutionary position. The basal position of C. The respective branching in our GapB subtree fig. A crucial finding of this study is the presence of GapB in the enigmatic unicellular green alga M. This scaly flagellate was previously classified as a prasinophyte Mattox and Stewart , but ultrastructural features proposed a placement together with charophytes Melkonian In addition, molecular data are inconclusive, supporting either a branching prior to green plants Chloro- and Streptophyta on the basis of mitochondrial and plastid genomes Lemieux, Otis, and Turmel ; Turmel, Otis, and Lemieux or a placement together with charophytes on the basis of single-gene and plastid genome phylogenies Bhattacharya et al.
However, the discovery of GapB in Mesostigma provides unequivocal support for the streptophycean affiliation of this green alga. Furthermore, our phylogenetic analyses support a placement at the base of all charophytes and reject a position together with or basal to chlorophytes fig. The exact timing of this event, which accordingly marks the origin of land plant evolution, is quite difficult, but recent molecular estimates for the split of streptophytes and chlorophytes range from to MYA Douzery et al.
The sequence data from A. Major financial support, including a Ph. Baalmann, E. Scheibe, R. Cerff, and W. Functional studies of chloroplast glyceraldehydephosphate dehydrogenase subunits A and B expressed in Escherichia coli : formation of highly active A4 and B4 homotetramers and evidence that aggregation of the B4 complex is mediated by the B subunit carboxy terminus. Plant Mol. Bhattacharya, D. The phylogeny of plastids: a review based on comparison of small-subunit ribosomal RNA coding regions.
Algal phylogeny and the origin of land plants. Plant Physiol. Weber, S. An, and W. Actin phylogeny identifies Mesostigma viride as a flagellate ancestor of the land plants. Bremer, K. Summary of green plant phylogeny and classification. Cladistics 1 : — Humphries, D. Mishler, and S. On cladistic relationships in green plants. Taxon 36 : — Brinkmann, H. Cerff, M. Green algae in the order Charales, and the coleochaetes, microscopic green algae that enclose their spores in sporopollenin, are considered the closest-living relatives of embryophytes.
The Charales can be traced as far back as million years. They live in a range of fresh water habitats and vary in size from as small as a few millimeters to as large as a meter in length. A representative species of Charales is Chara, which is often called muskgrass or skunkweed because of its unpleasant smell. Charophyte algae : A representative charophyte alga, Chara, is a noxious weed in Florida, where it clogs waterways. In Charales, large cells form the thallus: the main stem of the alga.
Branches arising from the nodes are made of smaller cells. Male and female reproductive structures are found on the nodes; the sperm have flagella. Unlike land plants, Charales do not undergo alternation of generations in their lifecycle. Like embryophytes, Charales exhibit a number of traits that are significant in their adaptation to land life.
They produce the compounds lignin and sporopollenin. They form plasmodesmata, which are microscopic channels that connect the cytoplasm of adjacent cells. The egg and, later, the zygote, form in a protected chamber on the parent plant.
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