ABSTRACT: There were two genotypes:,(1) Columbia-0, wild-type (C),(2) pmr4-1 mutant (P), callose synthase deficient mutant (Vogel and Somerville (2000) Proc. Natl. Acad. Sci., USA 97: 1897).,There were two treatments:,(1) uninoculated (U),(2) 3 days after inoculation with the powdery mildew pathogen, Erysiphe cichoracearum, race UCSC (I).,There were four biological replicates, labeled 1, 2, 3 or 4.,Examples of the sample labels are:,CU1 = Columbia-0, uninoculated, replicate 1,CI2 = Columbia-0, 3 days after inoculation with powdery mildew, replicate 2,PU3 = pmr4-1, uninoculated, replicate 3,PI4 = pmr4-1, 3 days after inoculation with powdery mildew, replicate 4.,In total, there were 16 Affymetrix ATH1 GeneChips (2 genotypes x 2 treatments x 4 biological replicates).