cDNA microarray analysis of fusicoccin-induced changes in gene expression in tomato plants

The effects of the fungal toxin fusicoccin (FC) on the tomato (Lycopersicon esculentum Mill.) transcriptome were analyzed in the context of defense-related genes using a spotted microarray of 235 cDNAs. Pronounced changes in transcript abundance were observed for 64 (27%) of the represented genes. FC appears to have an antagonistic effect on wound and pathogen defense responses, in that it causes the induction of pathogenesis-related and the down-regulation of wound response genes. The transcripts for many proteins involved in photosynthesis and carbohydrate metabolism were strongly repressed. Genes related to the biosynthesis of jasmonic acid and aromatic amino acids, on the other hand, were found to be up-regulated. In addition to these expression changes, which occurred rather late after FC treatment, rapid and transient induction kinetics were observed for a small group of genes encoding a calcium-dependent protein kinase, two mitogen-activated protein kinases, a matrix metalloproteinase and a homologue of the respiratory burst oxidase. These genes have not been described previously in tomato, nor has their regulation by FC been reported. Salicylic acid was shown not to be required for the induction of these transcripts and a function for the respective proteins in the FC-induced, salicylic acid-independent activation of pathogenesis-related genes is discussed.