Streptophyta

Coleochaete sp., copyright Micropolitan.org.

Belongs within: Diaphoretickes.
Contains: Umbellinaceae, Charopsida, Zygnematophyceae, Embryophyta.

The Streptophyta are a clade uniting the land plants (Embryophyta) with their closest allies among the green algae. Most species have a non-motile vegetative phase in the life cycle. Plesiomorphic streptophytes possess asymmetrical motile cells with a pair of cilia lacking mastigonemes; basal bodies have a distinctive multilayered structure of microtubular rootlet and cytoskeletal anchor (Adl et al. 2012). Basal members of the streptophyte lineage include the unicellular scaly alga Mesostigma viride (Karol et al. 2001). As well as the organic scales covering the cell wall and flagella, this species has the flagella emerging from a pit. Other basal streptophytes include Chlorokybus atmophyticus, a subaerial alga growing as sarcinoid packets of cells with hairs on zoospore flagella. Molecular analysis indicates that the freshwater unicellular genus Spirotaenia, previously included in the Zygnematophyceae due to its sexual reproduction via conjugation, is also a more basal streptophyte related to Mesostigma and Chlorokybus (Wickett et al. 2014). The type species, Spirotaenia condensata, is characterised by relatively large, cylindrical cells (over 100 µm long) with broadly rounded poles. Spirotaenia minuta is small, up to 40 µm long, and cells are fusiform with subacute apices.

The Klebsormidiophyceae grow as coccoid cells or unbranched filaments. Cells possess one or two chloroplasts with one pyrenoid, with most chloroplasts being parietal. Cells form a cleavage furrow during cell division but no cell plate or phragmoplast (Adl et al. 2012). Klebsormidium grows as typical uniseriate filaments that reproduce vegetatively. In the genus Interfilum, filaments fragment early in development so this genus is typically unicellular. Filaments of Entransia fimbriata may appear to bear short branches; these 'pseudobranches' are in fact the result of germinating reproductive cells that initially remain attached to the parent filament. Entransia fimbriata is further distinguished by highly lobed chloroplasts with multiple pyrenoids, and a single large vacuole per cell.

Members of the Coleochaetales, Characeae and Embryophyta are united by the presence of branching growth, oogamous sexual reproduction and phragmoplastic cell division. A phragmoplast is a cylindrical structure containing opposing arrays of actin filaments and microtubules that acts as a scaffold for cell plate formation. The Coleochaetales have discoid thalli of cells or branched filaments with sheathed hairs forming extensions of the cell walls (Adl et al. 2012). They are found in fresh water, commonly as epiphytes on aquatic plants. Chaetosphaeridium grows as branched filaments of globose or flask-shaped cells, or as a gelatinous colony of unicells. Coleochaete may form prostrate or erect branched filaments, with prostrate filaments sometimes adhered to form pseudoparenchyma, or as parenchymatous thalli. Asexual reproduction in Coleochaetales is via zoospores that are formed two to four per cell in Chaetosphaeridium but singly in Coleochaete. Sexual reproduction is oogamous.

Characters (from Adl et al. 2012, as Charophyta): Asymmetric motile cells, when present, with pair of cilia without mastigonemes; basal bodies with distinctive multilayered structure of microtubular rootlet and cytoskeletal anchor; thylakoids stacked; plastid with two membranes without periplastid endoplasmic reticulum; starch inside plastid; open mitosis; usually with phycoplast, but some with phragmoplast and cell plate; with primary plasmodesmata between adjacent cells in filamentous forms; filaments branching or nonbranching; with nonmotile vegetative phase; some with multinucleate cells; with or without sexual reproduction; sexual species with haplobiontic life cycle; with desiccation-resistant cysts (zygospores); glycolate oxidase in peroxisomes; Cu/Zn superoxide dismutase; ciliary peroxisome.

Streptophyta (see below for synonymy) WM14
    |  i. s.: Umbellinaceae E03
    |         Columbella ningbingensis E03
    |         Praechara Birina 1948 WH78
    |         Neochara huananensi NG13
    |         Grovesichara changzhouensis NG13
    |         Obtusochara prisca NG13
    |--+--Mesostigma Lauterborn 1894 WM14, AS12 [Mesostigmatales, Mesostigmatophyceae]
    |  |    `--M. viride WM14
    |  `--+--Chlorokybus Geitler 1942 WM14, AS12 [Chlorokybales, Chlorokybophyceae, Chlorokybophyta]
    |     |    `--C. atmophyticus WM14
    |     `--Spirotaenia WM14
    |          |--*S. condensata WM14
    |          `--S. minuta WM14
    `--+--Klebsormidiophyceae AS12
       |    |--Interfilum AS12
       |    |--Entransia Hughes 1943 AS12, MK00
       |    |    `--E. fimbriata WM14
       |    `--Klebsormidium [Klebsormidiales, Klebsormidiobiotes, Klebsormidiophyta] WM14
       |         |  i. s.: K. subtile WM14
       |         |--K. flaccidum KM01
       |         `--+--K. nitens KM01
       |            `--K. subtilissimum KM01
       `--Phragmoplastophyta AS12
            |--Charopsida WM14
            `--+--Coleochaetales [Chaetophycidae, Coleochaetophyceae] WM14
               |    |--Chaetosphaeridium [Chaetosphaeridiobiotes, Chaetosphaeridiophyceae, Chaetosphaeridiophyta] WM14
               |    |    |--C. globosum WM14
               |    |    `--C. ovalis KM01
               |    `--Coleochaete [Coleochaetobiotes, Coleochaetophyta] WM14
               |         |  i. s.: C. scutata WM14
               |         |--+--C. irregularis KM01
               |         |  `--C. sieminskiana KM01
               |         `--+--C. orbicularis KM01
               |            `--C. soluta KM01
               `--+--Zygnematophyceae WM14
                  `--Embryophyta WM14

Streptophyta [Charophyceae, Charophyta, Eophyceae, Phragmophytina, Rudophytae, Stichophycidae, Streptobionta, Zygnemobiotes] WM14

*Type species of generic name indicated

REFERENCES

[AS12] Adl, S. M., A. G. B. Simpson, C. E. Lane, J. Lukeš, D. Bass, S. S. Bowser, M. W. Brown, F. Burki, M. Dunthorn, V. Hampl, A. Heiss, M. Hoppenrath, E. Lara, E. Le Gall, D. H. Lynn, H. McManus, E. A. D. Mitchell, S. E. Mozley-Stanridge, L. W. Parfrey, J. Pawlowski, S. Rueckert, L. Shadwick, C. L. Schoch, A. Smirnov & F. W. Spiegel. 2012. The revised classification of eukaryotes. Journal of Eukaryotic Microbiology 59 (5): 429–493.

[E03] Edgell, H. S. 2003. Upper Devonian Charophyta of Western Australia. Micropaleontology 49 (4): 359–374.

[KM01] Karol, K. G., R. M. McCourt, M. T. Cimino & C. F. Delwiche. 2001. The closest living relatives of land plants. Science 294: 2351–2353.

[MK00] McCourt, R. M., K. G. Karol, J. Bell, K. M. Helm-Bychowski, A. Grajewska, M. F. Wojciechowski & R. W. Hoshaw. 2000. Phylogeny of the conjugating green algae (Zygnemophyceae) based on rbcL sequences. Journal of Phycology 36: 747–758.

[NG13] Ni, X., D. L. Gebo, M. Dagosto, J. Meng, P. Tafforeau, J. J. Flynn & K. C. Beard. 2013. The oldest known primate skeleton and early haplorhine evolution. Nature 498: 60–64.

[WH78] Wang Z. & Huang R.-J. 1978. Triassic charophytes of Shaanxi. Acta Palaeontologica Sinica 17 (3): 267–276.

[WM14] Wickett, N. H., S. Mirarab, N. Nguyen, T. Warnow, E. Carpenter, N. Matasci, S. Ayyampalayam, M. S. Barker, J. G. Burleigh, M. A. Gitzendanner, B. R. Ruhfel, E. Wafula, J. P. Der, S. W. Graham, S. Mathews, M. Melkonian, D. E. Soltis, P. S. Soltis, N. W. Miles, C. J. Rothfels, L. Pokorny, A. J. Shaw, L. DeGeronimo, D. W. Stevenson, B. Surek, J. C. Villarreal, B. Roure, H. Philippe, C. W. dePamphilis, T. Chen, M. K. Deyholos, R. S. Baucom, T. M. Kutchan, M. M. Augustin, J. Wang, Y. Zhang, Z. Tian, Z. Yan, X. Wu, X. Sun, G. K.-S. Wong & J. Leebens-Mack. 2014. Phylotranscriptomic analysis of the origin and early diversification of land plants. Proceedings of the National Academy of Sciences of the USA 111 (45): E4859–E4868.

Last updated: 9 January 2022.