developmental symbiosis: integrating life histories through gene expression

Eco-Devo Workshop

Program/Abstract # 47The plasticity of sexMinoru TanakaLaboratory of Molecular Genetics for Reproduction,National Institute for Basic Biology, Japan

How sex is determined has been a topic of long standing broadinterest. There are many types of sex determination system; geneticsystems with different sex determination genes and environmentalsystem with different critical temperatures. The subsequent processof sex differentiation following sex determination is not alwaysstraightforward. Some visual and neural system causes sex reversalduring their life cycle and the endocrine system seems integrated inthe mechanism of sex. These imply that some external and internalstimuli affect sex differentiation processes. Recent studies raise thepossibility that these stimuli might cause unbalance between germcells and somatic cells in some vertebrates. The balancing sex isconceptually important to understand establishment and mainte-nance of two different sexes, whose mechanism may be presentbehind many aspects of the phenotypic plasticity of sex. In this talk, Iwould like to raise open questions regarding the plasticity of sex anddiscuss about some possible mechanisms behind a variety of sexdifferentiation processes.

doi:10.1016/j.ydbio.2010.05.079

Program/Abstract # 48Developmental symbiosis: Integrating life histories throughgene expressionScott F. GilbertDept. of Biology, Swarthmore College, Swarthmore, PA, USA

Organisms do not develop autonomously. Rather, organisms haveevolved to respond to signals from the outside environment. In manyinstances, these signals come from symbiotic organisms such asbacteria, fungi, algae, or protists. This appears to be the “rule” formost species. In some instances, the symbiosis has become essentialfor the development of one of its partners, as in the wasp Asobara,where the Wolbachia bacteria are needed for the development of thefemale reproductive tract. Here, the bacteria are transmitted throughthe female germline in the same way as mitochondria. In other cases,symbionts are acquired by infection, as in the mammalian gut, whichacquires bacteria from the mother. The gut bacteria induce specificgene expression in the intestinal cells, and they are needed for theformation of the villi capillaries and gut-associated lymphoid tissue.

In some arthropods, infection by symbionts can change the sex of thecarrier from male to female. These developmental associations areextremely important in medicine and conservation biology. Parasiticworms have been killed by antimicrobial drugs, and herbicides canprevent the development of salamanders by killing the algalsymbionts needed by the eggs. We have “outsourced” importantdevelopmental signals to symbionts, and this opens an entire newarea for developmental biology.

doi:10.1016/j.ydbio.2010.05.080

Program/Abstract # 49Disruption of normal development with exogenous agentsKathleen K. SulikDept. of Cell and Dev. Biol., University of North Carolina,Chapel Hill, NC, USA

The developmental basis of disease as it relates to prenatalexposure to endocrine-disrupting chemicals (EDCs) and to theteratogens, retinoic acid and alcohol, will be described. EDCs are ahighly heterogeneous group of synthetic and natural chemicals thatinterfere with natural blood-borne hormones that are responsible forhomeostasis, reproduction, and developmental processes. Among thesynthetic EDCs are polychlorinated biphenyls (PCBs), dioxins,diethylstilbesterol (DES), and some plastics (e.g. bisphenol A),plasticizers (phthalates), pesticides, and fungicides. The phytoestro-gens, genistein and coumestrol, are examples of naturally-occurringEDCs. While a common target for many of these agents is thereproductive system, the mechanisms underlying EDC-induceddisorders are diverse. Transgenerational effects have been reportedand may result from overt mutation or epigenetic changes. The key todevelopmental/disease endpoints is the time in development whenexposure to the causative exogenous agent occurs. In defining criticalperiods for induction of a wide range of abnormalities, includingthose of the urogenital tract, animal model systems have beenemployed. Notable in this regard are studies of retinoic acid and ofalcohol-mediated teratogenesis following acute maternal exposureduring narrow windows of development. The dysmorphogenesis thatresults from these teratogenic insults will be illustrated and criticalperiods for the induction of Retinoic Acid Embryopathy and FetalAlcohol Spectrum Disorders in human populations will be discussed.Supported by NIH grants AA011605, AA017124, and AA019211.

doi:10.1016/j.ydbio.2010.05.081

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Developmental Biology

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Developmental Biology 344 (2010) 429