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The genome of the social amoeba Dictyostelium discoideum.

ABSTRACT: The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a high proportion of which have long, repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal ribosomal DNA (rDNA) element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal-fungal lineage after the plant-animal split, but Dictyostelium seems to have retained more of the diversity of the ancestral genome than have plants, animals or fungi.

SUBMITTER: Eichinger L

PROVIDER: S-EPMC1352341 | biostudies-literature | 2005 May

REPOSITORIES: biostudies-literature

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The genome of the social amoeba Dictyostelium discoideum.

Eichinger L L Pachebat J A JA Glöckner G G Rajandream M-A MA Sucgang R R Berriman M M Song J J Olsen R R Szafranski K K Xu Q Q Tunggal B B Kummerfeld S S Madera M M Konfortov B A BA Rivero F F Bankier A T AT Lehmann R R Hamlin N N Davies R R Gaudet P P Fey P P Pilcher K K Chen G G Saunders D D Sodergren E E Davis P P Kerhornou A A Nie X X Hall N N Anjard C C Hemphill L L Bason N N Farbrother P P Desany B B Just E E Morio T T Rost R R Churcher C C Cooper J J Haydock S S van Driessche N N Cronin A A Goodhead I I Muzny D D Mourier T T Pain A A Lu M M Harper D D Lindsay R R Hauser H H James K K Quiles M M Madan Babu M M Saito T T Buchrieser C C Wardroper A A Felder M M Thangavelu M M Johnson D D Knights A A Loulseged H H Mungall K K Oliver K K Price C C Quail M A MA Urushihara H H Hernandez J J Rabbinowitsch E E Steffen D D Sanders M M Ma J J Kohara Y Y Sharp S S Simmonds M M Spiegler S S Tivey A A Sugano S S White B B Walker D D Woodward J J Winckler T T Tanaka Y Y Shaulsky G G Schleicher M M Weinstock G G Rosenthal A A Cox E C EC Chisholm R L RL Gibbs R R Loomis W F WF Platzer M M Kay R R RR Williams J J Dear P H PH Noegel A A AA Barrell B B Kuspa A A

Nature 20050501 7038

The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a high proportion of which have long, repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exp ...[more]

PMID: 15875012

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Project description:Huntingtin is a large HEAT repeat protein first identified in humans, where a polyglutamine tract expansion near the amino terminus causes a gain-of-function mechanism that leads to selective neuronal loss in Huntington's disease (HD). Genetic evidence in humans and knock-in mouse models suggests that this gain-of-function involves an increase or deregulation of some aspect of huntingtin's normal function(s), which remains poorly understood. As huntingtin shows evolutionary conservation, a powerful approach to discovering its normal biochemical role(s) is to study the effects caused by its deficiency in a model organism with a short life-cycle that comprises both cellular and multicellular developmental stages. To facilitate studies aimed at detailed knowledge of huntingtin's normal function(s), we generated a null mutant of hd, the HD ortholog in Dictyostelium discoideum. Dictyostelium cells lacking endogenous huntingtin were viable but during development did not exhibit the typical polarized morphology of Dictyostelium cells, streamed poorly to form aggregates by accretion rather than chemotaxis, showed disorganized F-actin staining, exhibited extreme sensitivity to hypoosmotic stress, and failed to form EDTA-resistant cell-cell contacts. Surprisingly, chemotactic streaming could be rescued in the presence of the bivalent cations Ca(2+) or Mg(2+) but not pulses of cAMP. Although hd(-) cells completed development, it was delayed and proceeded asynchronously, producing small fruiting bodies with round, defective spores that germinated spontaneously within a glassy sorus. When developed as chimeras with wild-type cells, hd(-) cells failed to populate the pre-spore region of the slug. In Dictyostelium, huntingtin deficiency is compatible with survival of the organism but renders cells sensitive to low osmolarity, which produces pleiotropic cell autonomous defects that affect cAMP signaling and as a consequence development. Thus, Dictyostelium provides a novel haploid organism model for genetic, cell biological, and biochemical studies to delineate the functions of the HD protein.

Dataset Information

The genome of the social amoeba Dictyostelium discoideum.

Publications

The genome of the social amoeba Dictyostelium discoideum.

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