RNA-seq of rose-Diplocarpon rosae interactions

Black spot disease, caused by the hemibiotrophic fungus Diplocarpon rosae, represents a major threat for garden roses. Indeed, with the reduction or even sometimes the prohibition of agrochemical use and the increasing demand for roses with a higher degree of resistance, it is essential to investigate the mechanisms of resistance to this disease in roses. In this study, we explored the possible pathways involved in the immune response during D. rosae infection for two interaction types: a compatible interaction on Rosa chinensis 'Old Blush' and an incompatible interaction on a hybrid of Rosa wichurana. We conducted a comparative study of the transcriptomic changes that happen during the infection process in these two genotypes using a time course approach with a multi-series experiment. The experiments were performed in the greenhouse using a whole plant assay with four times points (0, 3, 5 and 7 days post-inoculation) and three biological replicates. The transcriptomic analysis enabled us to characterize the RW defense response: first, a quick immune response (PTI) leads to the activation of genes involved in callose deposition in papillae, and then an effector specific response (ETI) results in a HR. In contrast, the PTI response is inhibited at the early stages of infection in the susceptible genotype R. chinensis 'Old Blush', which exhibited a partial ETI probably involving specific recognition of fungal effectors.