Identification of rust-induced genes in poplar using Populus 4.6K cDNA macroarray

cDNA macroarray 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 either with spores of avirulent strain 93ID6 (incompatible interaction, I) or spores of virulent strain 98AG31 (compatible interaction, C) of the pathogenic rust fungus Melampsora larici-populina. Besides, we mock-inoculated 'Beaupré' leaves with water (control condition, T). Detached leaves were maintained in vitro in controled conditions to allow fungal infection and colonization of plant tissue. Leaves were sampled at 12, 24 and 48 hours post-inoculation (hpi) in a time-course experiment before (12 hpi) and after (24 and 48 hpi) that the fungus attempt to penetrate plant cells in mesophyll. Keywords: Plant tissue infection, Plant defense response, cDNA macroarray Three biological replicates named Rep1, Rep2 and Rep3 were obtained for each treatment (i.e., T, C and I) at each timepoint (i.e., 12, 24, 48 hpi). At each timepoint, two comparisons were performed: control treatment T versus compatible interaction C on one side and control treatment T versus incompatible interaction I on the other side. For each comparison, biological triplicates were used to identify transcripts significantly differentially accumulated between treatments at the considered timepoint using the CyberT statistical framework.