Brassica oleracea-Alternaria brassicicola interaction during the early stages of leaf infection. Brassica oleracea-Alternaria brassicicola interaction during the early stages of leaf infection

Gene expression changes during the initial stages of black spot disease caused by Alternaria brassicicola on Brassica oleracea (Brassica oleracea var. capitata f. alba, white cabbage) leaves were investigated with Arabidopsis thaliana oligonucleotide microarrays. Transcriptional profiling of infected B. oleracea leaves revealed that photosynthesis was the most negatively regulated biological process. The negative regulation of 6 photosynthesis-related genes, mainly the genes involved in the photosynthesis light reaction and Calvin cycle, was observed as early as 12 hours post infection (hpi). It progressed through 48-hpi stage, when 44 down-regulated photosynthesis-related genes were detected. The analyses of infected leaves at microscopic, ultrastructural and physiological levels supported the microarray-based observations and indicated that the photosynthetic processes are suppressed in B. oleracea as a result of the fungal infection. Overall design: Time-course experiment, two-color, common reference design, involving two biological replicates for each time point. Samples represent plant leaves harvested before infection (0hpi) and at different time points post infection with fungus (12h, 24h and 48h). Each biological replicate sample was prepared from leaves harvested from three plants. Cy-5 labeled samples for each time point and each replicate were individually hybridized to Cy3-labeled common reference (representing pooled RNA samples from mock-treated plants, harvested at the same time points as infected plants), on a total of 8 microarrays.