Identification of rust-induced genes in poplar using Populus PICME 28K cDNA microarrays

Microarray expression profiling was carried out in poplar leaves upon infection with rust in order to identify genes expressed during tree defense response. For this purpose, we inoculated detached leaves of the interamerican hybrid poplar Populus trichocarpa x Populus deltoides 'Beaupré' grown in greenhouse with spores of avirulent strain 93ID6 of the pathogenic rust fungus Melampsora larici-populina (incompatible interaction, I48). Besides, we mock-inoculated 'Beaupré' leaves with water (control condition, T48). Detached leaves were maintained in vitro in controled conditions to allow fungal infection and colonization of plant tissue. Leaves were sampled 48 hours post-inoculation after that the fungus attempt to penetrate plant cells in mesophyll. Competitive hybridization between transcripts of incompatible interaction (I48) and control condition (T48) was done on Populus PICME 28K cDNA microarray. Keywords: Time-course infection of plant tissue, defense response, cDNA microarray Three biological replicates of comparison between I48 and T48 treatments were tested, and one was discarded because of post-processing hybridization problems. Comparison between the two biological replicates served to identify consistent expression data in this experiment.