非メバロン酸経路関連遺伝子AtMEPCTのアンチセンス植物におけるジベレリン生合成遺伝子発現の定量

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Isopentenyl diphosphate (IDP), which is a general precursor of plant isoprenoids, can be synthesized by two different pathways, namely the mavalonate (MVA) pathway in cytosol and the non-MVA pathway in plastids. Since enzymes catalyzing early steps of gibberellins (GA) and abscisic acid (ABA) biosynthesis localize in plastids, the plastidial non-MVA pathway is thought to be a major pathway to supply the precursor for these plant hormones. AtMEPCT gene is the Arabidopsis homolog of the E. coli ygbP gene encoding 2-C-methyl-D-erythritol-4-phosphate (MEP) cytidylyltransferase that catalyzes the third step of the non-MVA pathway to produce cytidylyl-MEP. We generated antisensing plants for the AtMEPCT gene after cloning and its functional analysis. The transgenic plants showed pale green albino-like phenotype which was also seen on the plant treated with non-MVA pathway specific inhibitor, fosmidomycin, suggesting that the AtMEPCT gene affects the production of pigments such as carotenoids and chlorophylls through the plastidial non-MVA pathway. Some antisensing plants showed dwarf dwarf phenotype resembling gibberellin biosynthetic mutant, also indicating that defect of the non-MVA pathway may cause insufficient GA level in plant. To know if GA levels in antisensing plant decrease or not, we have been trying quantitstive RT-PCR method to examine the expression level of GA biosynthetic genes which are known to be upregulated when GA level decreased in plant. Preliminary results showed that the expression of GA 3β hydroxylase gene in antisensing plant slightly increased compared with wild type plant. Further detailed analysis is now proceeding.
2000-11-02

非メバロン酸経路関連遺伝子AtMEPCTのアンチセンス植物におけるジベレリン生合成遺伝子発現の定量

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