SMBE 2019 poster: Heterothallism as the ancestral state in Phyllosticta genus

Phyllosticta genus comprises many plant pathogens, endophytes and saprophytes, and they differ in their biology and ecology by many aspects, such as the system of sexual reproduction, which plays an important role in the plant diseases caused by this genus. Some species, such as P. capitalensis, P. abieticola and P. musarum, are known to be homothallic due to the ascospores production in pure cultures. Other species, such as P. citricarpa and P. citribraziliensis, were suggested as heterothallic based in genomic analysis of the mating-type locus. However, for most of the Phyllosticta species, the mating strategies are unknown, as there is no information available on ascospores production, crossing studies or genomic data. In order to investigate the evolution of mating strategies in Phyllosticta genus, we performed an ancestral character reconstruction analysis in Mesquite using a multilocus phylogenetic tree (ITS, tef1, act, gapdh) of Phyllosticta and Botryosphaeriaceae species to map the characters. Species were defined as heterothallic, homothallic or unknown based in genomic data and taxonomic characterizations available in the literature. Our results suggest that heterothallism is the ancestral state in Phyllosticta genus and the most-likely mating-strategy for the Phyllosticta species in which the thallism state is unknown. In addition, there were at least four shifts from heterothallism to homothallism in Phyllosticta genus. These results contribute to the understanding of the different mating strategies of Phyllosticta species under an evolutionary approach, in order to promote better comprehension of the mechanisms involved in sexual reproduction and its role in different plant diseases.