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A proposed model for mating type determination in Phytophthora infestans

Liyun Guo: China Agricultural University

<div><em>Phytophthora infestans</em> is the causal agent of late blight, the most devastating disease on potato. <em>P. infestans</em> is a heterothallic oomycete, which commonly requires two opposite mating types, A1 and A2 to complete sexual reproduction. Sexual reproduction is important for disease epidemics and the evolution of the pathogen, which will input difficulty for disease management. In a recent survey of <em>P. infestans</em> population in China, many self-fertile isolates were obtained and their ability of α hormones production and reception were assayed using polycarbonate membrane method described by Ko. Results showed that these self-fertile isolates could receive α hormone produced by themselves, just like homothallic <em>Phytophthora</em> spp. Based on these findings and the facts that the inheritance of the mating type doesn’t follow the Mandelian inheritance and the sexual reproduction of <em>Phytophthora</em> is hormonal regulated, we proposed a hypothesis that the genes encoding the production and the reception of α1 and α2 hormones co-exist in each genome of heterothallic <em>P. infestans</em> isolate, the expression of these genes are regulated by a epigenetic mechanism and determine the appearance of mating type of the isolate. This proposed model is helpful to explore the mechanisms of sexual reproduction and the regulation of hormone production and reception in oomycete.</div>