|Budget Amount *help
¥6,800,000 (Direct Cost : ¥6,800,000)
Fiscal Year 1993 : ¥2,400,000 (Direct Cost : ¥2,400,000)
Fiscal Year 1992 : ¥4,400,000 (Direct Cost : ¥4,400,000)
To date, we have identified 150 single, recessive mutations affecting embryogenesis in rice. Phenotypic characterization enabled them to be categorized into seven groups. 1. lethality at the early globular stage, 2. deletion of basal region, 3. deletion of ogans, 4. modified embryo size, 5. abnormal organ position, 6. abnormal mprphology of organs, and 7. variable abnormal phenotypes in spite of single nutation. This categorization indicates at least five regulatory processes are operating during embryogenesis : 1. pattern formation, 2. determination of organ differentiation, 3. regulation of embryo size, 4. regulation of organ position, and 5. morphogenesis of organs. In each process, two types of genes are detected ; one functioning in the whole embryo and the other functioning locally, in a specific organ. The present study also revealed that embryo size was controlled in two ways. When endosperm is reduced by the mutation of endosperm-specific gene, scutellum becomes giant without affecting shoot and root sizes. On the other hand, embryo-specific genes thus far identified regulate every organ size.
We have isolated a clone which was expressed specifically in the callus cultured for seven days on a embryo-inducing medium. This clone is expressed in zygotic embryo but not in shoots, roots or flowers. another clone is expressed commonly in embryo-inducing medium and adventitious bud-inducing medium, but not callus-inducing medium. These two clones would play important roles in embryogenesis and organ differentiation.