ABSTRACT: In this study we show the comparative transcriptome of constitutive subtilisin3 (csb3) plants, an Arabidopsis mutant showing strikingly enhanced resistance to biotrophic pathogens. CSB3 encodes a 1-hydroxy-2-methyl-2-butenyl 4-diphosphate synthase, the enzyme controlling the penultimate step of the biosynthesis of isopentenyl diphosphate via the 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway in the chloroplast. It has been proposed that CSB3 represents a point of metabolic convergence modulating the magnitude of SA-mediated disease resistance to biotrophic pathogens. We show that csb3 have increased expression of a set of genes encoding defense-related proteins and enzymes, which includes two subtilisins. In essence our results substantiates an important role of these two subtilases in the activation of defense-related signaling pathways against biotrophic pathogens. 5 five-week-old plants were collected, frozen in liquid nitrogen and stored at -80ºC. Samples from Col-0 and csb3 were compared.