Joint transcriptomic and proteomic approaches to precise the molecular basis of a major QTL (RUS) controlling quantitative rust resistance in poplar
Résumé
Foliar rust is the most devastating disease affecting European poplar plantations. One major QTL (Rus), identified in a Populus deltoides x P. trichocorpa pedigree, is on the process of positional cloning. To precise the molecular basis of Rus, joint proteomic and transcriptomic approaches were used to characterize differential expression 2 and 4 days post inoculation (dpi) in two bulks (Rus vs rus) of 10 progenies. At 2 dpi, few transcripts showed an altered expression in the Rus bulk, while genes known to be targeted by resistance genes in plant pathosystems, were found up-regulated 4 dpi. The rus bulk did not present such gene up-regulation while several transcripts, including defense-related genes, were down-regulated as early as 2 dpi. Changes in the proteome were studied by 2-D PAGE analysis and MS/MS characterization of a selected subset of 50 protein spots at 2 and 4 dpi. Interestingly, the proteins overexpressed in the Rus genotypes correlated quite well with the transcriptomic data. All the results, including data coming from positional cloning, suggested that Rus activates the same genes than those involved in qualitative resistance, but this activation is delayed in the quantitative response.