A novel phyllosphere residentProtomycesspecies that interacts with theArabidopsisimmune system

Abstract

ABSTRACTWe describe the genome contents of sixProtomycesspp. that are pathogenic within the typical host range of the genus and a novelProtomycesstrain (SC29) that was previously isolated from the phylloplane of wildArabidopsis thaliana(Arabidopsis), an atypical or possible alternate host. Genome-wide phylogenetic analysis defined SC29 as a distinctProtomycessp. Analysis of gene family expansions, gene retention, and gene loss patterns among theseProtomycesspp. lead us to hypothesize that SC29 may have undergone a host jump. The role of phyllosphere residency in the lifecycle ofProtomycesspp. was previously unknown. Genomic changes in SC29 and all otherProtomycesspp. were consistent with adaptations to the plant phylloplane. As predicted by our analysis of its mating locus, SC29 did not cause disease onArabidopsisas a single strain, but could persist in its phylloplane, while the closely relatedP. inouyeidoes not. SC29 treatedArabidopsisexhibited enhanced immunity againstBotrytis cinereainfection, associated with activation of MAPK3/6, camalexin, and SA-signalling pathways. We conclude that SC29 is a novelProtomycessp. able to survive in theArabidopsisphylloplane and that phylloplane residency is an important element in the lifecycle ofProtomycesspp.