Microarray analysis of med16, med8, elp2, and wild type (Col-0) infected with the necrotrophic fungal pathogen Sclerotinia sclerotiorum

The goal of the microarray experiment was to identify defense genes that were differentially expressed in the Arabidopsis mutants med16, med8, elp2, wild type in response to infection of the necrotrophic fungal pathogen Sclerotinia sclerotiorum. Results indicated that, compared with the wild type, the jasmonic acid (JA) biosynthesis genes LOX3, AOC3, and OPR3, ethylene (ET) biosynthesis genes ACS2 and ACS8, as well as salicylic acid (SA) biosynthesis genes ICS1 and EDS5 were up-regulated in med16 in local tissues at 1 day post-inoculation (dpi) and/or systemic tissues at 4 dpi. Surprisingly, however, while a number of SA pathway genes (EDS1, PAD4, NPR1, WRKY18, WRKY38, WRKY53, PR1, and PR2) and several JA-regulated wound-responsive genes (MYC2, JAR1, VSP1, and VSP2) were up-regulated in med16, a group of JA/ET-regulated defense genes (ORA59, ERF1, ERF14, PDF1.2, PDF1.2b, PDF1.2c, PDF1.3, PR4, and ChiB) and PR5 were down-regulated. On the other hand, only a few of these genes were differentially expressed between med8 or elp2 and the wild type. Three biological replicates with leaves from 8-12 plants per sample were collected at 0, 1, 2, and 4 days post-inoculation (dpi) after inoculation with the necrotrophic fungal pathogen Sclerotinia sclerotiorum. Leaf tissues were collected as controls at 0 dpi, the inoculated leaves were collected as local tissues at 1 dpi, and the upper uninoculated leaves were collected as systemic tissues at 2 and 4 dpi. After extraction, RNA concentration was determined on a NanoDrop Spectrophotometer (Thermofisher Scientific, Waltham, MA) and sample quality was assessed using the 2100 Bioanalyzer (Agilent Technologies, Santa Clara, CA). Equal amount of RNA from the 3 biological replicates were used for microarray analysis.