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.
Overall design: 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.
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