| Budget Amount *help |
¥7,000,000 (Direct Cost: ¥7,000,000)
Fiscal Year 1989: ¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1988: ¥4,200,000 (Direct Cost: ¥4,200,000)
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| Research Abstract |
Agrobacterium tumefaciens harboring the Ti Plasmid incites crown gall Tumor on a wide variety of dicotyledonous plants. Upon infection of plants, T-DNA of the Ti plasmid is transferred by unknown mechanisms to plant cells and integrated into plant nuclear DNA. The transfer of T-DNA requires virulence (vir) genes which are present in the Ti plasmid. Most vir genes are expressed in response to such plant signal molecules as acetosyringone and lignin precursors. Our previous results showed that such signal molecules are present in monocotyledonous plants plants which are thought to be resistant to Agrobacterium in addition to dicotyledonous. During purification of these monocotyledonous inducers, we found that some substance extracted from homogeneities of monocotyledonous seedlings markedly enhanced vir induction by signal molecules. Ciroumstantial evidence that the enhancing substances are monosaccharides or their derivatives. We examined whether or not commercially available sugars enhance vir induction. The results show that a group of aldoses (D-glucose, D-galactose, L-arabinose and D-xylose) that are known precursors of major cell wall monosaccharides, enhances vir induction wre than 10-fold. Likewise, 2-deoxy-D-glucose, a normetabolized sugar, is also effective. When a deletion was introduced into the coding region of the periplasmic region of VirA protein, enhancement by effective sugars disappeared, but vir expression was induced by the signal molecules in this mutant. These results suggest that these sugars directly accelerate a signaling process initiated by the inducers, which results in increase in increase in expression of the vir genes.
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