Dynamics of gamete chemotaxis in sexual reproduction

The persistence of binary mating systems in sexual organisms constitutes a well-known conundrum in evolutionary biology. In the majority of sexual organisms two different types of gametes are necessary for reproduction. The role of this asymmetry is unclear. Although different organisms have evolved various means of sexual reproduction, there is a common underlying process where specialized sexual cells (the gametes) need to recognize each other and fuse. For this to successfully occur the two gametes need to recognize each other somehow approach each other and effectively fuse. Therefore, communication between gametes is a vital aspect of the process. This is typically manifested via the generation and detection of chemical gradients. Various experimental reports suggest that gametes of different sex or mating type are attracted to each other via the release of and response to pheromones. What is more, the majority of these reports indicate that gametes of different type or sex take up different roles in this communication. In this work we aim to investigate the significance of this asymmetry in the function of the two gametes. We use mathematical modeling to explore the hypothesis that by being restricted to either secreting or releasing sexual pheromones the gametes achieve a more efficient mechanism of attraction whereby the speed at which they approach each other is optimized. The underlying hypothesis is that when a moving cell secretes a chemical it generates a local asymmetry in chemical concentration. We expect this to impair the chemoctactic movement of gametes secreting the same pheromone they are being attracted to. In this talk, I will present the approach and tools we used at the first stages of this work and I will show you some preliminary results.