| Budget Amount *help |
¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2001: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
Alternative splicing events in the 3'-terminal region of chloroplast ascorbate peroxidase (chlAPX) pre-mRNA in spinach and tobacco, which produced four types of mRNA variants, one form (tAPX-I) encoding thylakoid-bound APX (tAPX) and three forms (sAPX-I, -II, -III) encoding stromal APX (sAPX), were regulated in a tissue-specific manner. The ratio of the level of SAPX mRNAs (sAPX-I, -II, and -III) to tAPX-I mRNA was close to 1 in leaf, whereas the ratio in root was greatly elevated due to an increase in sAPX-III and a decrease in tAPX-I resulting from the alternative excision of intron 11 and intron 12, respectively. A putative splicing regulatory cis-element (SRE), which is highly conserved in the sequences of chlAPX genes of higher plants, was identified upstream of the acceptor site in intron 12. Gel-shift analysis showed that SRE interacts strongly with a nuclear protein from leaves, but not those from the roots of spinach and tobacco. These results indicate that the tissue-specific alternative splicing of chlAPX pre-mRNA is regulated by the splicing enhancer SRE.
Transgenic tobacco plants (TpTAP-12) overexpressing thylakoid membrane-bound ascorbate peroixdase (tAPX) targeted to chloroplasts were generated. The tAPX activity in TbTAP-12 plants was approximately 37-fold higher than that of the wild-type. The abilities of CO_2 fixation and PSII activity in between wild-type and TpTAP-12 plants were not changed.
The activities of thiol-modulated enzymes in the Calvin cycle, antioxidative enzymes, and levels of antioxidants were also same values in both plants. Transgenic tobacco plants -suppressing chloroplastic ascorbate peroixdase isoenzymes are generating using antisense technology.
Five lines of those plants at T_1 generation were isolated.
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