Methionine sulfoximine, an alternative selection for the bar marker in plants.

Methionine sulfoximine, like phosphinothricin (PPT), the active agent in the herbicide BASTA, is a glutamate analogue that inhibits growth of wildtype Arabidopsis plants through its action on glutamine synthetase. The bar gene, which confers resistance to PPT, also confers resistance to methionine sulfoximine. In this study we show that methionine sulfoximine is an effective and economical alternative to PPT as a selective agent in agar medium.

The ROOT MERISTEMLESS1/CADMIUM SENSITIVE2 gene defines a glutathione-dependent pathway involved in initiation and maintenance of cell division during postembryonic root development.

Activation of cell division in the root apical meristem after germination is essential for postembryonic root development. Arabidopsis plants homozygous for a mutation in the ROOT MERISTEMLESS1 (RML1) gene are unable to establish an active postembryonic meristem in the root apex. This mutation abolishes cell division in the root but not in the shoot. We report the molecular cloning of the RML1 gene, which encodes the first enzyme of glutathione (GSH) biosynthesis, gamma-glutamylcysteine synthetase, and which is allelic to CADMIUM SENSITIVE2. The phenotype of the rml1 mutant, which was also evident in the roots of wild-type Arabidopsis and tobacco treated with an inhibitor of GSH biosynthesis, could be relieved by applying GSH to rml1 seedlings. By using a synchronized tobacco cell suspension culture, we showed that the G(1)-to-S phase transition requires an adequate level of GSH. These observations suggest the existence of a GSH-dependent developmental pathway essential for initiation and maintenance of cell division during postembryonic root development.