Article

Heritable germ and somatic cell lineage competitions in chimeric colonial protochordates

Department of Developmental Biology , Stanford University, Palo Alto, California, United States
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 09/1999; 96(16):9148-53. DOI: 10.1073/pnas.96.16.9148
Source: PubMed

ABSTRACT Theories of evolution that state natural selection acts on individuals have been modified to include multiple levels of selection. Here we demonstrate in chimeric protochordates that primitive germ cell (pgc) and somatic cell (psc) lineages have traits that also make them likely units of natural selection. Specifically, by using microsatellites to determine the genetic identity of various somatic and gametic tissues within vascularly fused Botryllus schlosseri chimeras, we show that genetically distinct pgc and psc can compete for access to developing gonads and somatic organs, and that this competition is hierarchical, reproducible, and heritable. Given that a single, highly polymorphic locus (Fu/HC) controls whether two contacting colonies fuse or reject, our findings also support a leading hypothesis for why the highly polymorphic histocompatibility loci common to many metazoa may have arisen or been maintained: to limit supercompetitor lineages to histocompatible kin.

0 Followers
 · 
73 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ontologies provide an important resource to integrate information. For developmental biology and comparative anatomy studies, ontologies of a species are used to formalize and annotate data that are related to anatomical structures, their lineage and timing of development. Here, we have constructed the first ontology for anatomy and asexual development (blastogenesis) of a bilaterian, the colonial tunicate Botryllus schlosseri. Tunicates, like Botryllus schlosseri, are non-vertebrates and the only chordate taxon species that reproduce both sexually and asexually. Their tadpole larval stage possesses structures characteristic of all chordates, i.e. a notochord, a dorsal neural tube, and gill slits. Larvae settle and metamorphose into individuals that are either solitary or colonial. The latter reproduce both sexually and asexually and these two reproductive modes lead to essentially the same adult body plan. The Botryllus schlosseri Ontology of Development and Anatomy (BODA) will facilitate the comparison between both types of development. BODA uses the rules defined by the Open Biomedical Ontologies Foundry. It is based on studies that investigate the anatomy, blastogenesis and regeneration of this organism. BODA features allow the users to easily search and identify anatomical structures in the colony, to define the developmental stage, and to follow the morphogenetic events of a tissue and/or organ of interest throughout asexual development. We invite the scientific community to use this resource as a reference for the anatomy and developmental ontology of B. schlosseri and encourage recommendations for updates and improvements.
    PLoS ONE 05/2014; 9(5):e96434. DOI:10.1371/journal.pone.0096434 · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Fusion between multicellular individuals is possible in many organisms with modular, indeterminate growth, such as marine invertebrates and fungi. Although fusion may provide various benefits, fusion usually is restricted to close relatives by allorecognition, also called heterokaryon or somatic incompatibility in fungi. A possible selective explanation for allorecognition is protection against somatic parasites. Such mutants contribute less to colony functions but more to reproduction. However, previous models testing this idea have failed to explain the high diversity of allorecognition alleles in nature. These models did not, however, consider the possible role of spatial structure. We model the joint evolution of allorecognition and somatic parasitism in a multicellular organism resembling an asexual ascomycete fungus in a spatially explicit simulation. In a 1,000-by-1,000 grid, neighboring individuals can fuse, but only if they have the same allotype. Fusion with a parasitic individual decreases the total reproductive output of the fused individuals, but the parasite compensates for this individual-level fitness reduction by a disproportional share of the offspring. Allorecognition prevents the invasion of somatic parasites, and vice versa, mutation towards somatic parasitism provides the selective conditions for extensive allorecognition diversity. On the one hand, if allorecognition diversity did not build up fast enough, somatic parasites went to fixation; conversely, once parasites had gone to fixation no allorecognition diversity built up. On the other hand, the mere threat of parasitism could select for high allorecognition diversity, preventing invasion of somatic parasites. Moderate population viscosity combined with weak global dispersal was optimal for the joint evolution of allorecognition and protection against parasitism. Our results are consistent with the widespread occurrence of allorecognition in fungi and the low degree of somatic parasitism. We discuss the implications of our results for allorecognition in other organism groups.
    Fungal Genetics and Biology 10/2014; DOI:10.1016/j.fgb.2014.09.010 · 3.26 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Botryllus schlosseri is a colonial ascidian with characteristics that make it an attractive model for studying immunology, stem cell biology, evolutionary biology, and regeneration. Transcriptome sequencing and the recent completion of a draft genome sequence for B. schlosseri have revealed a large number of genes, both with and without vertebrate homologs, but analyzing the spatial and temporal expression of these genes in situ has remained a challenge. Here we report a robust protocol for in situ hybridization that enables the simultaneous detection of multiple transcripts in whole adult B. schlosseri using Tyramide Signal Amplification in conjunction with digoxigenin- and dinitrophenol-labeled RNA probes. Using this protocol we have identified a number of genes that can serve as markers for developing and mature structures in B. schlosseri, permitting analysis of phenotypes induced in loss-of-function experiments. © 2014 Wiley Periodicals, Inc.
    genesis 09/2014; 53(1). DOI:10.1002/dvg.22820 · 2.04 Impact Factor

Full-text (2 Sources)

Download
33 Downloads
Available from
Jun 10, 2014