Differential Regulation of the Expression in Transgenic Tobacco of the Gene for r{beta}-Glucuronidase under the Control of the 5'-Upstream Regions of Two Catalase Genes from Castor Bean

The regulatory functions of the 5'-flanking regions of two genesfor catalase (cat1 and cat2) from castor bean were analyzedin transgenic tobacco plants that carried fusion constructsthat included the gene for rß-glucuronidase (GUS)for Escherichia coli. Dry mature seeds from transgenic plantscarrying the CAT1-GUS or CAT2-GUS constructs, in which the GUSgene was fused to the 5'-flanking region of cat1 or cat2, respectively,contained significant GUS activity, indicating that the promotersof cat1 and cat2 were active during seed development. GUS activityincreased in response to germination in the seeds of transgenictobacco that carried CAT1-GUS, as well as in those that carriedCAT2-GUS. During the post-germinative stage the GUS activitydirected by CAT2-GUS increased still further, whereas that directedby CAT1-GUS decreased. The changes in GUS activity in the transgenictobacco plants that carried CAT1-GUS and CAT2-GUS were similarto the changes in the levels of transcripts of cat1 and cat2,respectively, in castor bean. The results suggest that the expressionof cat1 and cat2 in the germinating seeds and postgerminativeseedlings is regulated mainly at the level of transcription.However, the distribution of GUS activity among the organs ofthe transgenic tobacco seedlings and plantlets, which was examinedby histochemical staining and by enzymatic assays of tissueextracts, was not identical to that of transcripts of cat1 andcat2 in castor bean. Histochemical analysis also revealed theinteresting spatial regulation of the expression of the promoterof cat2 in the transgenic tobacco seedlings. ¹Present address: Center for Molecular Biology and Genetics,Mie University,1515 Kamihama, Tsu, 519 Japan²Present address: Faculty of Biotechnology, Fukui PrefecturalUniversity, 4-1-1 Kenjojima, Matsuoka-cho, Yoshida-gun, Fukui,910-11 Japan