| Budget Amount *help |
¥4,010,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥510,000)
Fiscal Year 2007: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
Fiscal Year 2006: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
We isolated an embryo pattern formation mutant, multiple shoot1 (msh1) in rice. The first abnormality of these mutants was observed in embryogenesis. Before 7 days after pollination (DAP), we could not discriminate msh1 embryo from wild-type embryo. At 13 DAP, embryos with fewer leaves and lacking root cap were found, suggesting that development of the msh1 embryo was retarded compared to the wild-type embryo. In the msh1 embryo at this stage, the basal region was abnormally enlarged. In mature embryos, ectopic shoot and/or roots were formed in the basal region. In most of msh1 embryos, one ectopic root is formed, resulting in two roots in total. Ectopic shoot was observed in about half of embryos examined. Ectopic shoot was always underdeveloped. Thus, msh1 could have defect in proper apical-basal patterning at the later stage, causing ectopic differentiation of shoot and root in the basal region. The msh1 plants were dwarf and bushy. The multiple shoot phenotype seemed to be caused by at least two reasons. One is the reduced dormancy of axillary buds: in, contrast to that the axillary bud of the wild-type first leaf is dormant, that of msh1 frequently elongated to become a tiller. Another reason is the ectopic formation of shoots. Leaves of msh1 plant were short, and lacked collars, ligules and auricles, and blade-sheath boundary was unclear. The blade of the msh1 leaves was underdeveloped. In some cases, the leaves seemed to comprise only sheath. The msh1 plants did not enter the reproductive phase. These results show that msh1 has pleiotropic effects on the growth and patterning of leaves, tissue differentiation, adventitious bud formation, and bud dormancy. To map the MSH1 locus, we analyzed the F2 population and found that MSH1 is located near the centromere on chromosome 8.
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