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Evolution of size and pattern in the social amoebas.

Schaap P - Bioessays (2007)

Bottom Line: The foundation is a recently constructed molecular phylogeny of the Dictyostelia, which was used to examine trends in the evolution of novel forms and in the divergence of genes that shape these forms.The role of cAMP in aggregation arose through co-option of a pathway that originally acted to coordinate fruiting body formation.The genotypic changes that caused this innovation and the role of dynamic cAMP signaling in defining fruiting body size and pattern throughout social amoeba evolution are discussed.

View Article: PubMed Central - PubMed

Affiliation: College of Life Sciences, University of Dundee, MSI/WTB/JBC complex, Dow Street, Dundee DD1 5EH, UK. p.schaap@dundee.ac.uk

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Fruiting body morphologies in different social amoeba spec es. A: D. vinaceo-fuscumfruiting bodies showaclustered habit and crampon-like support structures. B: D. polycephalum displays a coremiform (bunched) habit. C: P. pallidum fruiting bodies are decorated with regular whorls of side-branches. D: D. rosarium fruiting body with ancillary sessile sori. E: D. discoideum fruiting body with supporting basal disc. Bar lengths are 100 μ. Photographs courtesy of Andrew R. Swanson (Manatee Community College) and Frederick W. Spiegel (University of Arkansas).
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fig02: Fruiting body morphologies in different social amoeba spec es. A: D. vinaceo-fuscumfruiting bodies showaclustered habit and crampon-like support structures. B: D. polycephalum displays a coremiform (bunched) habit. C: P. pallidum fruiting bodies are decorated with regular whorls of side-branches. D: D. rosarium fruiting body with ancillary sessile sori. E: D. discoideum fruiting body with supporting basal disc. Bar lengths are 100 μ. Photographs courtesy of Andrew R. Swanson (Manatee Community College) and Frederick W. Spiegel (University of Arkansas).

Mentions: Social amoebas also have a trophic amoeboid stage, but they achieve macroscopic dimensions by aggregation.3 This occurs in response to starvation, which triggers regulated secretion of chemoattractant by the amoebas (Fig. 1). Cellular agglomerates are formed, which can consist of up to a million amoebas. Sophisticated cell–cell signalling mechanisms between the amoebas orchestrate the differentiation of up to five different cell types and coordinate an intricate progression of cell movements. In combination with the synthesis of a flexible skin-like matrix, cell differentiation and cellular movement first generate the formation of a motile structure, called the “slug”. The slug responds to chemical gradients and to light and warmth, which cause it to move to the soil's top layer. Here, the slug projects upwards and forms the fruiting body. This again involves highly ordered movement and differentiation and yields a slender column of stalk cells that bears aloft a global mass of spores. Depending on the species, the stalkcan show different patterns of side branches and/or be decorated with disc, root or cup-shaped support structures (Fig. 2). Unlike the ontogeny of sessile organisms like plants and fungi, which depends largely on series of directional cell divisions, the formation of fruiting bodies in social amoebas is more similar to the ontogeny of animal form. Both depend strongly on an intertwined program of cell movement and cell differentiation.


Evolution of size and pattern in the social amoebas.

Schaap P - Bioessays (2007)

Fruiting body morphologies in different social amoeba spec es. A: D. vinaceo-fuscumfruiting bodies showaclustered habit and crampon-like support structures. B: D. polycephalum displays a coremiform (bunched) habit. C: P. pallidum fruiting bodies are decorated with regular whorls of side-branches. D: D. rosarium fruiting body with ancillary sessile sori. E: D. discoideum fruiting body with supporting basal disc. Bar lengths are 100 μ. Photographs courtesy of Andrew R. Swanson (Manatee Community College) and Frederick W. Spiegel (University of Arkansas).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3045520&req=5

fig02: Fruiting body morphologies in different social amoeba spec es. A: D. vinaceo-fuscumfruiting bodies showaclustered habit and crampon-like support structures. B: D. polycephalum displays a coremiform (bunched) habit. C: P. pallidum fruiting bodies are decorated with regular whorls of side-branches. D: D. rosarium fruiting body with ancillary sessile sori. E: D. discoideum fruiting body with supporting basal disc. Bar lengths are 100 μ. Photographs courtesy of Andrew R. Swanson (Manatee Community College) and Frederick W. Spiegel (University of Arkansas).
Mentions: Social amoebas also have a trophic amoeboid stage, but they achieve macroscopic dimensions by aggregation.3 This occurs in response to starvation, which triggers regulated secretion of chemoattractant by the amoebas (Fig. 1). Cellular agglomerates are formed, which can consist of up to a million amoebas. Sophisticated cell–cell signalling mechanisms between the amoebas orchestrate the differentiation of up to five different cell types and coordinate an intricate progression of cell movements. In combination with the synthesis of a flexible skin-like matrix, cell differentiation and cellular movement first generate the formation of a motile structure, called the “slug”. The slug responds to chemical gradients and to light and warmth, which cause it to move to the soil's top layer. Here, the slug projects upwards and forms the fruiting body. This again involves highly ordered movement and differentiation and yields a slender column of stalk cells that bears aloft a global mass of spores. Depending on the species, the stalkcan show different patterns of side branches and/or be decorated with disc, root or cup-shaped support structures (Fig. 2). Unlike the ontogeny of sessile organisms like plants and fungi, which depends largely on series of directional cell divisions, the formation of fruiting bodies in social amoebas is more similar to the ontogeny of animal form. Both depend strongly on an intertwined program of cell movement and cell differentiation.

Bottom Line: The foundation is a recently constructed molecular phylogeny of the Dictyostelia, which was used to examine trends in the evolution of novel forms and in the divergence of genes that shape these forms.The role of cAMP in aggregation arose through co-option of a pathway that originally acted to coordinate fruiting body formation.The genotypic changes that caused this innovation and the role of dynamic cAMP signaling in defining fruiting body size and pattern throughout social amoeba evolution are discussed.

View Article: PubMed Central - PubMed

Affiliation: College of Life Sciences, University of Dundee, MSI/WTB/JBC complex, Dow Street, Dundee DD1 5EH, UK. p.schaap@dundee.ac.uk

Show MeSH