Molecular Studies on Dormancy, Fruit Development and Growth Regulation in Deciduous Fruit Trees

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Morphogenesis of fruit trees are quite important problems in fruit growing. But the biochemical studies, in particular the techniques of molecular biology, have been scarcely applied to clarify the physiological regulation of morphogenesis in fruit tree. Elucidation of the mechanisms that regulate the growth and development of fruit tree will enable to establish the epochal cultivation techniques. However, not only the studies directly using the fruit trees as material, but also the basic studies using the model systems will provide new insights into the fruit tree development and novel approaches to clarify the physiological phenomena which are important for fruit tree science.To clarify the mechanism of dormancy, we identified the genes differentially expressed in pea axillary buds after the release of apical dominance. In conclusion, the maintenance and the break of dormancy is regulated by the cross talk of phytohormones such as auxin, cytokinin and abscisic acid.To clarify the mechanism of fruit coloring, we generated the in vitro assay system using the apple callus derived from flesh cells. Our results clearly demonstrated that the in vivo activity ofanthocyanin biosynthetic enzymes are controlled by the light conditions and the levels of mineral nutrients.With the aim of generating dwarf plants, we modified the level of gibberellin (GA), in transgenic plants by overproduction of a GA catabolic enzyme. Theses transformants showed dwarf or semi-dwarf. Stability and inheritance of these traits demonstrate the feasibility of genetic improvement of cereal crops by modulation of GA catabolism and bioactive GA contents.