Chimaeric ribonuclease genes that are expressed in the anthers of transformed tobacco and oilseed rape plants were constructed. Chimaeric ribonu clease gene expression within the anther selec tively destroys the tapetal cell layer that surrounds the pollen sac, prevents pollen formation, and leads to male sterility. These nuclear male sterility genes should facilitate the production of hybrid seed in various crop plants.

A two-component cloning system to transfer foreign DNA into plants was derived from the octopine Ti plasmid pTiB6S3. pGV2260 is a non-oncogenic Ti plasmid from which the T-region is deleted and substituted by pBR322. pGV831 is a streptomycin-resistant pBR325 derivative that contains a kanamycin resistance marker gene for plant cells and a site for cloning foreign genes between the 25-bp border sequences of the octopine T-region. Conjugative transfer of pGV831 derivatives to Agrobacterium and cointegration by homologous recombination between the pBR322 sequences present on pGV831 and pGV2260, can be obtained in a single step. Strains carrying the resulting cointegrated plasmids transfer and integrate T-DNA into the genome of tobacco protoplasts, and transformed tobacco calli are readily selected as resistant to kanamycin. Intact plants containing the entire DNA region between the T-DNA borders have been regenerated from such clones. In view of these properties we present pGV831 and its derivatives as vectors for efficient integration of foreign genes into plants.

Phosphinothricin (PPT) is a potent inhibitor of glutamine synthetase in plants and is used as a non‐selective herbicide. The bar gene which confers resistance in Streptomyces hygroscopicus to bialaphos, a tripeptide containing PPT, encodes a phosphinothricin acetyltransferase (PAT) (see accompanying paper). The bar gene was placed under control of the 35S promoter of the cauliflower mosaic virus and transferred to plant cells using Agrobacterium‐mediated transformation. PAT was used as a selectable marker in protoplast co‐cultivation. The chimeric bar gene was expressed in tobacco, potato and tomato plants. Transgenic plants showed complete resistance towards high doses of the commercial formulations of phosphinothricin and bialaphos. These data present a successful approach to obtain herbicide‐resistant plants by detoxification of the herbicide.

No abstract

A Ti plasmid mutant was constructed in which all the on‐cogenic functions of the T‐DNA have been deleted and replaced by pBR322. This Ti plasmid, pGV3850, still mediates efficient transfer and stabilization of its truncated T‐DNA into infected plant cells. Moreover, integration and expression of this minimal T‐DNA in plant cells does not interfere with normal plant cell differentiation. A DNA fragment cloned in a pBR vector can be inserted in the pGV3850 T‐region upon a single recombination event through the pBR322 region of pGV3850 producing a co‐integrate useful for the transformation of plant cells. Based upon these properties, pGV3850 is proposed as an extremely versatile vector for the introduction of any DNA of interest into plant cells.