Identification of rust-induced genes in poplar using Populus 2.0 NimbleGen oligoarray

Oligoarray 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 I48) or spores of virulent strain 98AG31 (compatible interaction C48) of the pathogenic rust fungus Melampsora larici-populina. 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. Keywords: Plant tissue infection, Plant defense response, Oligonucleotide array Three biological replicates named Rep1, Rep2 and Rep3 were obtained for each treatment (i.e., T48, C48 and I48). Two comparisons were performed: control treatment T48 versus compatible interaction C48 on one side and control treatment T48 versus incompatible interaction I48 on the other side. For each comparison, biological triplicates were used to identify transcripts significantly differentially accumulated between treatments using the bayesreg script of the CyberT statistical framework.