Gonium
| Gonium | |
|---|---|
| |
| Gonium pectoraleMueller | |
Scientific classification
| |
| Clade: | Viridiplantae |
| Division: | Chlorophyta |
| Class: | Chlorophyceae |
| Order: | Chlamydomonadales |
| Family: | Goniaceae |
| Genus: | Gonium O. F. Muller,1773 |
| Species | |
Goniumis a genus of colonialalgae,a member of the orderChlamydomonadales.Typical colonies have 4 to 16 cells, all the same size, arranged in a flat plate, with no anterior-posterior differentiation. In a colony of 16 cells, four are in the center, and the other 12 are on the four sides, three each.[1]A description by G.M. Smith (1920, p. 94):[2]
GoniumMueller 1773: Colonies of 4-8-16 cells arranged in a flat quadrangular plate and embedded in a common gelatinous matrix or connected by broad gelatinous strands. Cells ovoid topyriform,with a single cup-shapedchloroplastcontaining onepyrenoid.Each cell with twociliaof equal length, contractilevacuolesat the base of the cilia, and aneyespot.Four- and eight-celled colonies with the cilia on the same side; sixteen-celled colonies with the four central cells having their cilia on the same side and the twelve marginal cells with radially arranged cilia.
Asexual reproduction by simultaneous division of all cells in the colony to formautocolonies,or by a formation of 2-4zoosporesin each cell.
Sexual reproductionisogamous,by a fusion ofbiciliatezoogametes.
Evolution
[edit]The genusGoniumrepresents species closely related to single celledChlamydomonasand multicellular differentiatedVolvox.The orderVolvocaleshas long been a well recognized model system for the study of multicellular evolution.Goniumand the familyTetrabaenaceaecontain species representative of colony formation among unicells.Gonium'smorphology of colonies of alike cells suggest it is more genetically similar toChlamydomonasthanVolvox,a fact confirmed by phylogenetic analysis.[3]
TheVolvocaleshave been hypothesized to have evolved in twelve discrete steps.[4]Gonium represents the first six evolutionary steps of multicellularity;[3](1) incomplete cytokinesis, (2) partial inversion, (3) rotation of the basal bodies, (4) organismal polarity, (5) transformation of the cell wall into extra-cellular matrix (ECM), (6) genetic control of cell number. Although the exact order and progression through David Kirk's twelve steps of multicellular evolution[4]are probably not necessarily linear and each occurs more dynamically than originally thought.[3]
Life cycle
[edit]Goniumbeing evolutionarily related toChlamydomonashas a life cycle that is derivative of that ofChlamydomonas.Goniumcells grow asexually as colonies of either 4, 8 or 16 colonial cells. Cell and colony growth ofGoniumis uncoupled from cell division just likeChlamydomonasand each cell within the colony divides by multiple-fission. Thus, each cell within the colony will divide 2, 3 or 4 times, thus producing 2"n"daughter cells, or 4, 8 or 16 cells within the colony. UnlikeChlamydomonaswhere each of the daughter cells separate from each other,Goniumdaughter cells remain attached to each other in their ECM.
The sexual cycle ofGoniumis also very similar to that ofChlamydomonas.The sexual program ofGoniumis induced by nitrogen deprivation where each vegetative cell within the colony differentiates in gametes.Goniumgametes are isogomous, or equal-sized, and unicellular. Thus unicellularGoniumgametes break apart from the multicellular colonies when the sexual program is initiated. Also likeChlamydomonas,there are two "sexes", plus or minus controlled by a genes homologous[5]to those found inChlamydomonasandVolvox.[6]
References
[edit]- ^Pennak, Robert W (1978).Fresh-Water Invertebrates of the United States(Second ed.).John Wiley & Sons.pp.43.ISBN0-471-04249-8.
- ^Smith, GM. Phytoplankton of Inland Lakes of Wisconsin, Part I, Wisconsin Geological and Natural History Survey, Madison, WI. (1920).
- ^abcHerron MD, Hackett JD, Aylward FO, Michod RE (2009)."Triassic origin and early radiation of multicellular volvocine algae".Proceedings of the National Academy of Sciences, USA.106(9): 3254–3258.Bibcode:2009PNAS..106.3254H.doi:10.1073/pnas.0811205106.PMC2651347.PMID19223580.
- ^abKirk, David L. (2005-02-15)."A twelve-step program for evolving multicellularity and a division of labor".BioEssays.27(3): 299–310.doi:10.1002/bies.20197.ISSN0265-9247.
- ^Hamaji, T.; Ferris, P. J.;Coleman, A. W.;Waffenschmidt, S.; Takahashi, F.; Nishii, I. & Nozaki, H. (2008)."Identification of the minus-dominance gene ortholog in the mating-type locus of Gonium pectoral".Genetics.178(1): 283–294.doi:10.1534/genetics.107.078618.PMC2206078.PMID18202374.
- ^Ferris, P. J.; Olson, B.; de Hoff, P. L.; Douglass, S.; Casero, D.; Prochnik, S. E.; Geng, S.; et al. (2010)."Evolution of an expanded sex-determining locus in Volvox".Science.328(5976): 351–354.Bibcode:2010Sci...328..351F.doi:10.1126/science.1186222.PMC2880461.PMID20395508.
External links
[edit]- Gonium- Description with pictures
- Michod Lab- Research overview of Dr. Richard Michod at the University of Arizona who studies multicellular evolution and whose lab published a detailed phylogenetic tree of theVolvocales
- VIP- The Volvocales Information Project led by Dr. Aurora M. Nedelcu at University of New Brunswick
- Olson LabArchived2015-03-06 at theWayback Machine- Dr. Bradley Olson at Kansas State University who studies multicellular evolution with methods for growing Gonium
- Nozaki Lab- Dr. Hisayoshi Nozaki at the University of Tokoyo who studies multicellular evolution and has cultured manyVolvocalesstrains, including Gonium
- Hallman Lab- Dr. Armin Hallman at Bielefeld University whose lab developed a method for transforming Gonium
- Lerche, K. & Hallmann, A. (2009)."Stable nuclear transformation of Gonium pectorale".BMC Biotechnology.9:64.doi:10.1186/1472-6750-9-64.PMC2720962.PMID19591675.
- UTEX- The UTEX algal culture collection which houses many Gonium strains including pictures
- CCAP- The CCAP algal culture collection which houses many Gonium strains including pictures