Gene expression after Verticillium longisporum infection in a susceptible and a resistant A. thaliana near isogenic line

Resistance against Verticillium longisporum is quantitative and multigenic. The vec1 QTL in Arabidopsis thaliana controlled resistance against systemic colonization by the fungus. Gene expression was studied to identify genes and pathways controlled by vec1. Near-isogenic lines derived from the resistant ecotype Bur and the susceptible ecotype Ler were compared. NIL9 contained Ler-alleles in the genomic region between 11753 and 12285 kb within vec1 on chromosome 2, tmNIL130 contained Bur-alleles. Microarrays were performed on samples containing the hypocotyl and the shoot basis because colonization is stopped in this region in resistant genotypes. Two developmental stages were studied: time-point (1) at the onset of flowering, when systemic colonization was shown to start and time point (2) at the onset of silique maturity, when extensive fungal proliferation was shown to occur. Two pathogen treatments were studied: (1) mock-inoculated controls, (2) plants inoculated with the V. longipsorum isolate 43 (VL). Gene expression was studied in two genotypes (NIL9-susceptible; tmNIL130-resistant), under two pathogen treatments (mock-inoculated; VL-inoculated) at two time points (at the onset of flowering, 13 days post inoculation [dpi]; at the onset of silique maturity, 27-29 dpi). Three biological replicates were used for each treatment (24 microarrays altogether).