specific probe a 1 4 kb transcript is seen in root flower and siliques fig7 the same size transcript was detected in leaves when more rna is loaded on the gel this data is shown in fig8 the 34 lan 34 sample the gene is expressed ubiquitously in the different tissues examined root leaf flower and silique but the message is most abundant in the silique there is differential expression in 4 week old rosette leaves between the wild type and mutants there is 3 to 4 fold more message expressed in the ems induced ga4 1 plants as compared to wild type but no message is detected in the t dna tagged ga4 2 plants fig8 the over expression of ga4 message detected in the ga4 1 plants can be repressed by the application of 10 5 m exogenous ga 3 ott the rosette leaves of arabidopsis the transcriptional repression can be detected at 8 hours after the initial treatment and lasts for up to 24 hours fig9 the over expression of ga4 message in the ems induced ga4 1 mutant and transcriptional regulation by exogenous ga 3 is a novel finding as regards the regulation of the gibberellin biosynthesis pathway the terminal gibberellins in arabidopsis are ga 1 and ga 4 which are effective in causing stem elongation talon m et al proc natl acad sci usa 87 7983 7987 1990 ga 3 has been shown to be present at low levels in vegetative tissue of maize ga 3 is biosynthesized from ga 20 via ga 5 and ga 1 is the product of ga 3 in maize fujioka s et al plant physiol 94 127.