Abstract
| - Plants resistant to the fungal pathogen Leptosphaeria maculans were generated by an interspecificcross between the highly susceptible Brassica napus (canola) and the highly resistant Brassicacarinata. Changes in the leaf protein profiles of these lines were investigated in order to understandthe biochemical basis for the observed resistance. Two-dimensional electrophoresis followed bytandem mass spectrometry led to the identification of proteins unique to the susceptible (5 proteins)and resistant genotypes (7 proteins) as well those that were differentially expressed in the resistantgenotype 48 h after challenge with the pathogen (28 proteins). Proteins identified as being unique inthe resistant plant material included superoxide dismutase, nitrate reductase, and carbonic anhydrase.Photosynthetic enzymes (fructose bisphosphate aldolase, triose phosphate isomerase, sedoheptulosebisphosphatase), dehydroascorbate reductase, peroxiredoxin, malate dehydrogenase, glutaminesynthetase, N-glyceraldehyde-2-phosphotransferase, and peptidyl-prolyl cis−trans isomerase wereobserved to be elevated in the resistant genotype upon pathogen challenge. Increased levels of theantioxidant enzyme superoxide dismutase were further validated and supported by spectrophotometricand in-gel activity assays. Other proteins identified in this study such as nitrate reductase andpeptidylprolyl isomerase have not been previously described in this plant−pathogen system, andtheir potential involvement in an incompatible interaction is discussed. Keywords: Brassicanapus; canola; Leptosphaeria maculans; mass spectrometry; proteomics;peptidylprolyl isomerase; superoxide dismutase
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