Comparative transcriptomic reveals signatures specific to various interactions with Melampsora rust fungi

We aim to understand the global transcriptional response of hybrid poplar NM6 (Populus nigra x Populus maximoviczii) to infection by two biotrophic Melampsora fungi, M. larici-populina and M. medusae f. sp. deltoidae separately and simultanously. Transcript profilling revealed 699 differentially expressed genes whose expression level was equal or higher than 2-fold between infected and noninfected tissues. In the mixed infection, our results showed an additive response of the two pathogens. Genes regulated as a result of Melampsora infection were generally induced and mainly involved in primary/secondary metabolism that include cell wall reinforcement and lignification, defense-related processes like pathogenesis-related and stress response, signal perception and transduction mechanisms and regulation of transcription. Keywords: Stress response Poplar leaves were infected with Melampsora larici-populina and Melampsora medusae f. sp. deltoidae and the mixture of them (Mixed infection). At six day post-infection, tissues were harvested for RNA extraction and hybridization on Affymetrix microarrays. Three biological replications were obtained from infected and non infected leaves (control samples).