Studies on the use of toxic precursor analogs of opines to select transformed plant cells.

S-(2-aminoethyl-)L-cysteine and L-canavanine were less toxic for octopine-type crown gall tissues that contained lysopine dehydrogenase than for other crown gall or habituated tissues. These analogs are substrates for lysopine dehydrogenase in vitro and in vivo. Thus toxic analogs of amino acid precursors of opines may be useful in selecting for cells that contain an opine dehydrogenase.