The use of phosphomannose-isomerase as a selectable marker to recover transgenic maize plants (Zea mays L.) via Agrobacterium transformation.

A new selectable marker system has been adapted for use in Agrobacterium-mediated transformation of maize. This selection system utilizes the pmi gene encoding for phosphomannose-isomerase that converts mannose-6-phosphate to fructose-6-phosphate. Only transformed cells are capable of utilizing mannose as a carbon source.

A central role of salicylic Acid in plant disease resistance.

Transgenic tobacco and Arabidopsis thaliana expressing the bacterial enzyme salicylate hydroxylase cannot accumulate salicylic acid (SA). This defect not only makes the plants unable to induce systemic acquired resistance, but also leads to increased susceptibility to viral, fungal, and bacterial pathogens. The enhanced susceptibility extends even to host-pathogen combinations that would normally result in genetic resistance.

Requirement of salicylic Acid for the induction of systemic acquired resistance.

It has been proposed that salicylic acid acts as an endogenous signal responsible for inducing systemic acquired resistance in plants. The contribution of salicylic acid to systemic acquired resistance was investigated in transgenic tobacco plants harboring a bacterial gene encoding salicylate hydroxylase, which converts salicylic acid to catechol. Transgenic plants that express salicylate hydroxylase accumulated little or no salicylic acid and were defective in their ability to induce acquired resistance against tobacco mosaic virus.

Regulation of pathogenesis-related protein-1a gene expression in tobacco.

Pathogenesis-related protein-1a (PR-1a) is a protein of unknown function that is strongly induced during the onset of systemic acquired resistance (SAR) in tobacco. The expression of PR-1a is under complex regulation that is controlled at least partially by the rate of transcription. In this study, we demonstrated that 661 bp of 5' flanking DNA was sufficient to impart tobacco mosaic virus and salicylic acid inducibility to a reporter gene.

Herbicide resistance due to amplification of a mutant acetohydroxyacid synthase gene.

We have selected a tobacco cell line, SU-27D5, that is highly resistant to sulfonylurea and imidazolinone herbicides. This line was developed by selection first on a lethal concentration of cinosulfuron and then on increasing concentrations of primisulfuron, both sulfonylurea herbicides. SU-27D5 was tested against five sulfonylureas and one imidazolinone herbicide and was shown, in every case, to be two to three orders of magnitude more resistant than wild-type cells.