Catharanthus roseus genes regulated differentially by mollicute infections

A differential display of mRNAs was used to isolate periwinkle cDNAs differ entially expressed following infection with one of three mollicutes: Spirop lasma citri, Candidatus Phytoplasma aurantifolia, and stolbur phytoplasma. Twenty-four differentially expressed cDNAs were characterized by Northern b lots and sequence analysis. Eight of them had homologies with genes in data banks coding for proteins involved in photosynthesis, sugar transport, resp onse to stress, or pathways of phytosterol synthesis. The regulation of the se genes in periwinkle plants infected by additional phloem-restricted bact eria showed that they were not specific to a given mollicute, but correlati ons with particular symptoms could be established. Expression of transketol ase was down regulated following infection with a pathogenic strain of S. c itri. No down regulation was observed for the nonphytopathogenic mutant GMT 553, which is deficient for fructose utilization.