ACTIVATION OF LATENT TRANSGENES IN ARABIDOPSIS USING A HYBRID TRANSCRIPTION FACTOR

A hybrid transcription factor comprising a fusion of the DNA-binding d omain of Saccharomyces cerevisiae GAL4 and the transcription activatio n domain of maize Cl was expressed in stably transformed Arabidopsis. Additional transgenic lines were created containing test genes control led by a synthetic promoter consisting of concatemeric copies of the c ia-acting site recognized by GAL4 (UASG) fused to a minimal promoter. The GAL4/Cl effector line was crossed to two lines containing a synthe tic promoter/GUS fusion. Both histochemical staining and GUS activity assays indicate strong activation of GUS expression was achieved only after crossing. The GAL4/Cl effector line was also crossed to 15 lines containing a synthetic promoter/ antisense adenylosuccinate synthetas e gene. Severely retarded growth, and in some cases lethality, was obs erved in 40% of the F-1 lines. This system of activation by crossing i s generally useful for activating expression of test transgenes.