Project description:Diseases of poplar caused by the fungal pathogen Sphaerulina musiva and related species are of growing concern, particular with the increasing interest in intensive popluliculture to meet increasing energy demands. S. musiva is able to cause infection on leaves, resulting in defoliation and canker formation on stems. To gain a greater understanding of the different responses of poplar species to infection with their natural Sphaerulina species, RNA-seq was conducted on leaves of Populus deltoides, P. balsamifera and P. tremuloides infected with S. musiva, S. populicola and a new undescribed species Ston1, respectively. Progression of disease symptoms, pathogen growth and host response were detected. Through the time course of infection, different and species-specific metabolic pathways were activated. In all three species, genes associated with growth and development were down-regulated, while genes involved the phenylpropanoid, terpenoid and flavonoid biosynthesis were up-regulated. Poplar defensive genes were expressed early in P. balsamifera and P. tremuloides, but delayed in P. deltoides, which correlated with the rate of disease symptoms development. This data gives an insight into the large differences in timing and expression of genes between poplar species being attacked with their native associated Sphaerulina pathogen.
Project description:Diseases of poplar caused by the fungal pathogen Sphaerulina musiva and related species are of growing concern, particular with the increasing interest in intensive popluliculture to meet increasing energy demands. S. musiva is able to cause infection on leaves, resulting in defoliation and canker formation on stems. To gain a greater understanding of the different responses of poplar species to infection with their natural Sphaerulina species, RNA-seq was conducted on leaves of Populus deltoides, P. balsamifera and P. tremuloides infected with S. musiva, S. populicola and a new undescribed species Ston1, respectively. Progression of disease symptoms, pathogen growth and host response were detected. Through the time course of infection, different and species-specific metabolic pathways were activated. In all three species, genes associated with growth and development were down-regulated, while genes involved the phenylpropanoid, terpenoid and flavonoid biosynthesis were up-regulated. Poplar defensive genes were expressed early in P. balsamifera and P. tremuloides, but delayed in P. deltoides, which correlated with the rate of disease symptoms development. This data gives an insight into the large differences in timing and expression of genes between poplar species being attacked with their native associated Sphaerulina pathogen. RNA-seq was conducted on leaves of Populus deltoides, P. balsamifera and P. tremuloides infected with S. musiva, S. populicola and a new undescribed species Ston1, respectively.
Project description:Pathogenic fungal infections in plants may, in some cases, lead to downstream systematic impacts on the plant metabolome and microbiome that may either alleviate or exacerbate the effects of the fungal pathogen. While Sphaerulina musiva is a well-characterized fungal pathogen which infects Populus tree species, an important wood fiber and biofuel feedstock, little is known about its systematic effects on the metabolome and microbiome of Populus. Here, we investigated the metabolome of Populus trichocarpa and Populus deltoides leaves and roots and the microbiome of the leaf and root endospheres, phylloplane, and rhizosphere to understand the systematic impacts of S. musiva abundance and infection on Populus species in a common garden field setting. We found that S. musiva is indeed present in both P. deltoides and P. trichocarpa, but S. musiva abundance was not statistically related to stem canker onset. We also found that the leaf and root metabolomes significantly differ between the two Populus species and that certain leaf metabolites, particularly the phenolic glycosides salirepin and salireposide, are diminished in canker-infected P. trichocarpa trees compared to their uninfected counterparts. Furthermore, we found significant associations between the metabolome, S. musiva abundance, and microbiome composition and α-diversity, particularly in P. trichocarpa leaves. Our results show that S. musiva colonizes both resistant and susceptible hosts and that the effects of S. musiva on susceptible trees are not confined to the site of canker infection. IMPORTANCE Poplar (Populus spp.) trees are ecologically and economically important trees throughout North America. However, many western North American poplar plantations are at risk due to the introduction of the nonnative fungal pathogen Sphaerulina musiva, which causes leaf spot and cankers, limiting their production. To better understand the interactions among the pathogen S. musiva, the poplar metabolome, and the poplar microbiome, we collected leaf, root, and rhizosphere samples from poplar trees consisting of 10 genotypes and two species with differential resistance to S. musiva in a common garden experiment. Here, we outline the nuanced relationships between the poplar metabolome, microbiome, and S. musiva, showing that S. musiva may affect poplar trees in tissues distal to the site of infection (i.e., stem). Our research contributes to improving the fundamental understanding of S. musiva and Populus sp. ecology and the utility of a holobiont approach in understanding plant disease.
Project description:Genetic and genomics tools to characterize host-pathogen interactions are disproportionately directed to the host because of the focus on resistance. However, understanding the genetics of pathogen virulence is equally important and has been limited by the high cost of de novo genotyping of species with limited marker data. Non-resource-prohibitive methods that overcome the limitation of genotyping are now available through genotype-by-sequencing (GBS). The use of a two-enzyme restriction-associated DNA (RAD)-GBS method adapted for Ion Torrent sequencing technology provided robust and reproducible high-density genotyping of several fungal species. A total of 5783 and 2373 unique loci, 'sequence tags', containing 16,441 and 9992 single nucleotide polymorphisms (SNPs) were identified and characterized from natural populations of Pyrenophora teres f. maculata and Sphaerulina musiva, respectively. The data generated from the P. teres f. maculata natural population were used in association mapping analysis to map the mating-type gene to high resolution. To further validate the methodology, a biparental population of P. teres f. teres, previously used to develop a genetic map utilizing simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers, was re-analysed using the SNP markers generated from this protocol. A robust genetic map containing 1393 SNPs on 997 sequence tags spread across 15 linkage groups with anchored reference markers was generated from the P. teres f. teres biparental population. The robust high-density markers generated using this protocol will allow positional cloning in biparental fungal populations, association mapping of natural fungal populations and population genetics studies.