準教授　Robert W. Ridge

最近の研究活動

  1. Investigation into the effects of Nod Factor (a presumptive signal molecule) on the biology of root hairs, using Nod Factor both as a tool in understanding early interactions of the Rhizobium/legume symbiosis and in understanding the basic processes of root hair growth. Most of the experimentation is at the light microscope level using Nomarski optics and time-lapse video recording. Experimental topics include the manipulation of cytoplasmic streaming and the basis of nuclear migration.

  2. The role of cell surface sugars at the tip of root hairs. It was discovered that a particular lectin (RCA-1) binds highly specifically to the root hair tips of some plant species. Current work is establishing how widespread the phenomenon is and how it can be manipulated; for the latter purpose Nod Factors are being used as tools to perturb the normal process of growth.

  3. Using the synthetic auxin 2,4-D, investigation into the induction of nodule-like structures on the cereals rice and wheat. The results so far have shown that these monocotyledons have the same in-built 'programming' for the development of nodules as do the dicotyledon legumes, and that perhaps the only barrier to establishing a nitrogen-fixing symbiosis is the initial 'molecular conversation' where the Rhizobium and plant communicate using flavone and lipo-oligosaccharide signal molecules. GUS-labelled rhizobia are being used to investigate the colonisation of roots and nodule-like structures.

  4. Cloning and investigating the role of myosin in plants. Myosin is well known in animal cells, especially as an active agent in the movement of muscle. It is also known in plants, but little is known about its function. However it is likely to be involved in intracellular movement as a cytoskeletal-associating protein. The model system for investigation is legume root hairs. Most of the research will be done in Australia.

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研究論文

  1. Ridge, R.W.: Micro-vesicles, pyriform vesicles and macro-vesicles associated with the plasma membrane in the root hairs of Vicia hirsuta after freeze-substitution, J. Plant Research, 108, 363-368 (1995).
    This work is part of a theme on understanding how the root hair grows. It was shown that besides being found endoplasmically, vesicles can also be found packaged close to the plasma membrane, these packages delineated by endoplasmic reticulum. In addition, this is the first report of micro-vesicles in root hairs, where they were found only in close association with the plasma membrane.

  2. Ridge, R.W.: Recent developments in the cell and molecular biology of root hairs, J. Plant Research, 108, 399-405 (1995).
    Recent results in root hair research show that these tip-growing cells are useful models in plant cell biology research. The review covers a range of topics, but there is particular emphasis on the use of mutants in molecular (genetic) analysis.

  3. Rolfe, B.G., Carlson, R.W., Ridge, R.W., Dazzo, F.B., Mateos, P.F. and Pankhurst, C.E.: Defective infection and nodulation of clovers by exopolysaccharide mutants of Rhizobium leguminosarum bv. trifolii., Australian J. Plant Physiology, 23, 184-203 (1996).
    This is an internationally cooperative work on the biological and symbiotic properties of two types of exopolysaccharide (EPS) deficient mutants of Rhizobium. The experiments showed that EPS is essential for the induction of rapid root hair curling, proper infection thread formation, and sustained growth of nodules. It is proposed that a key role of acidic EPS is to act as a signal molecule, modulating the components of the plant's disease defence system.

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研究発表

  1. Izumo, M., Katsumi, M. and Ridge, R.W.: Hormonal control of root hair growth in clover, 15th International conference on plant growth substances, Minneapolis, USA.,1995.

  2. Izumo, M., Ridge, R.W. and Katsumi, M.: Action of gibberellin on root hair growth, 59th Annual Meeting of the Botanical Society of Japan, Kanazawa, 1995.

  3. Kohiyama, M. and Ridge, R.W.: Colonisation of nodule-like structures on rice by GUS-labeled Rhizobium leguminosarum bv trifolii, 5th Annual Meeting of the Plant-Microbe Interactions Society of Japan, Kagoshima, 1995.

  4. Akao, S., Minagawa, Y., Taki, H., Minamizawa, T. and Ridge, R.W.: The construction and use of GUS-labeled Rhizobium, 5th Annual Meeting of the Plant-Microbe Interactions Society of Japan, Kagoshima,1995.

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著書・その他の出版物

  1. Ridge, R.W.: Root Hairs: Cell Biology and Development. In: (Y. Waisel, A. Eshel, U. Kafkafi, editors) Plant Roots: The Hidden Half. Marcel Dekker Inc, New York, 2nd edition,127-147 (1996).

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研究助成金・受賞等

  1. Japanese Ministry of Education International Scientific Research Program: Joint Research, for "Myosin - establishing its role in plants", as Research Leader. In collaboration with Dr Shimmen (Himeji Institute of Technology), Dr Williamson and Dr Plazinski (both of the Australian National University).

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学術団体における委員・役職

  1. International Rice Nodulation Group, 1991-present. Founding Member.

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