Genome sequence of the necrotrophic plant pathogen Pythium ultimum reveals original pathogenicity mechanisms and effector repertoire

Abstract

BackgroundPythium ultimum is a ubiquitous oomycete plant pathogen responsible for a variety of diseases on a broad range of crop and ornamental species.ResultsThe P. ultimum genome (42.8 Mb) encodes 15,290 genes and has extensive sequence similarity and synteny with related Phytophthora species, including the potato blight pathogen Phytophthora infestans. Whole transcriptome sequencing revealed expression of 86% of genes, with detectable differential expression of suites of genes under abiotic stress and in the presence of a host. The predicted proteome includes a large repertoire of proteins involved in plant pathogen interactions, although, surprisingly, the P. ultimum genome does not encode any classical RXLR effectors and relatively few Crinkler genes in comparison to related phytopathogenic oomycetes. A lower number of enzymes involved in carbohydrate metabolism were present compared to Phytophthora species, with the notable absence of cutinases, suggesting a significant difference in virulence mechanisms between P. ultimum and more host-specific oomycete species. Although we observed a high degree of orthology with Phytophthora genomes, there were novel features of the P. ultimum proteome, including an expansion of genes involved in proteolysis and genes unique to Pythium. We identified a small gene family of cadherins, proteins involved in cell adhesion, the first report of these in a genome outside the metazoans.ConclusionsAccess to the P. ultimum genome has revealed not only core pathogenic mechanisms within the oomycetes but also lineage-specific genes associated with the alternative virulence and lifestyles found within the pythiaceous lineages compared to the Peronosporaceae.

Transcriptome and secretome of two Pythium species during infection and saprophytic growth

“…These results support the hypothesis of Zerillo et al (2013) and others (Lévesque et al 2010) that globose sporangial Pythium species, including P. irregulare and P. iwayamai, are less effective at degrading suberized roots, leaves and stems than other plant pathogenic oomycetes that produce cutinases; nevertheless, they can penetrate leaves possibly through stomata. irregulare had fewer annotated PL/PE genes than other Pythium and Phytophthora species, and concluded that these species likely did not completely saccharify this complex sugar.…”

Finding a partner in the ocean: molecular and evolutionary bases of the response to sexual cues in a planktonic diatom

“…The genome size, N50 value and GC content were taken from the respective publications (Armbrust et al ., 2004; Bowler et al ., 2008; Cock et al ., 2010; Lévesque et al ., 2010; Lommer et al ., 2012; Tanaka et al ., 2015; Mock et al ., 2017). …”

Multiple Avirulence Loci and Allele-Specific Effector Recognition Control thePm3Race-Specific Resistance of Wheat to Powdery Mildew

“…This also implies that AvrPm3 a2/f2 is translocated into the plant cell. In the oomycete Pythium ultimum, a YxSL[KR] motif was found to be conserved among effectors specifically and highly expressed during infection (Lévesque et al, 2010), which somewhat resembles the YxC motif found in powdery mildew effectors, including AvrPm3 a2/f2 . One hypothesis is that the YxC motif could be involved in translocation of the effector protein inside the host cell.…”