title: Cell-cell signalling in sexual chemotaxis: a basis for gametic differentiation, mating types and sexes.
abstract: While sex requires two parents, there is no obvious need for them to be differentiated into distinct mating types or sexes. Yet this is the predominate state of nature. Here, we argue that mating types could play a decisive role because they prevent the apparent inevitability of self-stimulation during sexual signalling. We rigorously assess this hypothesis by developing a model for signaller-detector dynamics based on chemical diffusion, chemotaxis and cell movement. Our model examines the conditions under which chemotaxis improves partner finding. Varying parameter values within ranges typical of protists and their environments, we show that simultaneous secretion and detection of a single chemoattractant can cause a multifold movement impediment and severely hinder mate finding. Mutually exclusive roles result in faster pair formation, even when cells conferring the same roles cannot pair up. This arrangement also allows the separate mating types to optimize their signalling or detecting roles, which is effectively impossible for cells that are both secretors and detectors. Our findings suggest that asymmetric roles in sexual chemotaxis (and possibly other forms of sexual signalling) are crucial, even without morphological differences, and may underlie the evolution of gametic differentiation among both mating types and sexes.
authors.affiliation: Centre for Mathematics, Physics and Engineering in the Life Sciences and Experimental Biology (CoMPLEX), University College London, Gower Street, London WC1E 6BT, UK Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK zena.hadjivasiliou@ucl.ac.uk.
authors.forename: Zena
authors.initials: Z
authors.lastname: Hadjivasiliou
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Yoh
authors.initials: Y
authors.lastname: Iwasa
authors.affiliation: Centre for Mathematics, Physics and Engineering in the Life Sciences and Experimental Biology (CoMPLEX), University College London, Gower Street, London WC1E 6BT, UK Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Pomiankowski
mesh_terms: D002450:Cell Communication / Q000502:physiology*; D002633:Chemotaxis / Q000502:physiology*; D008954:Models, Biological; D015398:Signal Transduction / Q000502:physiology*
keywords: chemotaxis; mating types; sexes; signalling