New insights on evolutionary aspects of Pythium insidiosum and other peronosporaleans

Abstract

Summary Background The evolution of pathogenic mechanisms is a major challenge, which requires a thorough comprehension of the phylogenetic relationships of pathogens. Peronosporaleans encompasses a heterogeneous group of oomycetes that includes some animal/human pathogens, like Pythium insidiosum. Objective We analysed here the phylogenetic positioning and other evolutionary aspects related to this species and other peronosporaleans, using a multi‐locus approach with one mitochondrial and three nuclear genes. Methodology Phylogenetic patterns of 55 oomycetes were inferred by maximum likelihood and Bayesian analysis, and a relaxed molecular clock method was applied to infer the divergence time of some peronosporaleans branches. Results Pythium insidiosum was monophyletic with a major and polytomous clade of American isolates; however, Pythium spp. was found to be paraphyletic with Phytopythium sp. and Phytophthora spp. In general, peronosporaleans subdivided into four lineages, one of which evidenced a close relationship of P insidiosum, P aphanidermatum and P arrhenomanes. This lineage diverged about 63 million years ago (Mya), whereas P insidiosum diversified at approximately 24 Mya. The divergence of American and Thai isolates seems to have occurred at approximately 17 Mya, with further American diversification at 2.4 Mya. Conclusion Overall, this study clarifies the phylogenetic relationships of P insidiosum regarding other peronosporaleans in a multi‐locus perspective, despite previous claims that phylogenomic analyses are needed to accurately infer the patterns and processes related to the evolution of different lineages in this group. Additionally, this is the first time that a molecular clock was applied to study the evolution of P insidiosum.

Predicting Lifestyle from Positive Selection Data and Genome Properties in Oomycetes

“…The picture is not so clear for the heterotrophs and their adaptation to different hosts. Pythium insidiosum , a mammal parasite responsible for pythiosis, shows a relatively recent divergence from Pythium aphanidermatum and Pythium arrhenomanes , both of which are plant pathogens [ 22 ]. There are many theories that explain how such drastic host shifts can occur in a small evolutionary timescale [ 23 ].…”

Predicting Lifestyle and Host From Positive Selection Data and Genome Properties in Oomycetes

“…The picture is not so clear for the heterotrophs and their adaptations to different hosts. Pythium insidiosum, a mammal parasite responsible for pythiosis, shows a relatively recent divergence from Pythium aphanidermatum and Pythium arrhenomanes, both of which are plant pathogens [20]. How such drastic host shifts occur in a small evolutionary timescale is not fully understood.…”