TRANSPOSON TAGGING OF THE DEFECTIVE EMBRYO AND MERISTEMS GENE OF TOMATO

The shoot and root apical meristems (SAMs and RAMs, respectively) of h igher plants are mechanistically and structurally similar, This has le d previously to the suggestion that the SAM and RAM represent modifica tions of a fundamentally homologous plan of organization. Despite rece nt interest in plant development, especially in the areas of meristem regulation, genes specifically required for the function of both the S AM and RAM have not yet been identified. Here, we report on a novel ge ne, Defective embryo and meristems (Dem), of tomato, This gene is requ ired for the correct organization of shoot apical tissues of developin g embryos, SAM development, and correct cell division patterns and mer istem maintenance in roots. Dem was cloned using transposon tagging an d shown to encode a novel protein of 72 kD with significant homology t o YNV2, a protein of unknown function of Saccharomyces cerevisiae. Dem is expressed in root and shoot meristems and organ primordia but not in callus. The expression pattern of oem mRNA in combination with the dem mutant phenotype suggests that Dem plays an important role within apical meristems.