Activated cAMP receptors switch encystation into sporulation

Yoshinori Kawabe, Takahiro Morio, John L. James, Alan R. Prescott, Yoshimasa Tanaka, Pauline Schaap (Lead / Corresponding author)

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    26 Citations (Scopus)

    Abstract

    Metazoan embryogenesis is controlled by a limited number of signaling modules that are used repetitively at successive developmental stages. The development of social amoebas shows similar reiterated use of cAMP-mediated signaling. In the model Dictyostelium discoideum, secreted cAMP acting on 4 cAMP receptors (cARs1-4) coordinates cell movement during aggregation and fruiting body formation, and induces the expression of aggregation and sporulation genes at consecutive developmental stages. To identify hierarchy in the multiple roles of cAMP, we investigated cAR heterogeneity and function across the social amoeba phylogeny. The gene duplications that yielded cARs 2-4 occurred late in evolution. Many species have only a cAR1 ortholog that duplicated independently in the Polysphondylids and Acytostelids. Disruption of both cAR genes of Polysphondylium pallidum (Ppal) did not affect aggregation, but caused complete collapse of fruiting body morphogenesis. The stunted structures contained disorganized stalk cells, which supported a mass of cysts instead of spores; cAMP triggered spore gene expression in Ppal, but not in the cAR null mutant, explaining its sporulation defect. Encystation is the survival strategy of solitary amoebas, and lower taxa, like Ppal, can still encyst as single cells. Recent findings showed that intracellular cAMP accumulation suffices to trigger encystation, whereas it is a complementary requirement for sporulation. Combined, the data suggest that cAMP signaling in social amoebas evolved from cAMP-mediated encystation in solitary amoebas; cAMP secretion in aggregates prompted the starving cells to form spores and not cysts, and additionally organized fruiting body morphogenesis. cAMP-mediated aggregation was the most recent innovation.

    Original languageEnglish
    Pages (from-to)7089-7094
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume106
    Issue number17
    DOIs
    Publication statusPublished - 28 Apr 2009

    Keywords

    • Developmental signaling
    • Evolution of multicellularity
    • Dictyostelia
    • Amoebozoa
    • Adenylyl cyclase G
    • Dictyostelium discoideum (Dd)
    • Polysphondylium pallidum
    • Signal transduction
    • Social amebas
    • Prespore differentiation
    • Normal morphogenesis
    • Cyclic AMP
    • Gene
    • Protein

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