Outline of Research and Education
During embryogenesis in higher plants, special tissues called the shoot and root meristems are formed at the upper and lower ends, respectively. After germination, the shoot meristem forms above-ground organs such as leaves, stems and floral organs, while the root meristem produces underground roots. Both genetic controls and diverse external environmental factors such as light or gravity influence the formation of the plant body. By using Arabidopsis thaliana, a model crucifer plant suitable for molecular genetic analyses, we are studying molecular mechanisms that regulate plant development.
Major Research Topics
Polar auxin transport mechanisms
Polar auxin transport is involved in various growth responses including axis formation during embryogenesis, organogenesis, vascular patterning, apical dominance, and tropism. In the process, auxin efflux carriers play a key role. Auxin efflux carriers are localized to the plasma membrane with polarity in one cell and arranged in a uniform orientation in organs and tissues, which allow directional auxin transport through them. We have isolated and identified genes involved in localization of auxin efflux carrier with polarity by molecular genetic methods. The analyses of these genes demonstrate an important role of vesicle trafficking and signaling pathway in the establishment of polar localization of auxin efflux carrier. At present, we attempt to investigate the intercellular molecular network to establish the polarity.
Molecular mechanisms for auxin-dependent gene transcription
Auxin coordinates the transcription of numerous auxin-dependent genes through nuclear auxin receptor. Nuclear auxin receptor regulates the activity of transcription factors to control the synthesis of mRNA by RNA polymerase II. However, precise molecular mechanisms have not been elucidated yet. We are currently focusing on the Mediator complex, which conveys signals from transcription factors to RNA polymerase II machinery and general transcription factors, and seek to understand molecular mechanisms underlying auxin-dependent gene transcription.
Molecular mechanisms for secondary growth
Once the main primary body plans has been established by the activity of the shoot and root apical meristems, some plant species undergo secondary growth. The vascular cambium, a lateral meristem, produces continuously the vascular tissues through secondary growth and drives the radial thickenings of plant organs. Furthermore, during secondary growth another outside lateral meristem, the cork cambium, is formed. In Arabidopsis, secondary growth occurs in stems, roots and hypocotyl. We are focusing on the secondary growth-related lateral meristems, the vascular cambium and the cork cambium, and attempting to elucidate the regulatory mechanisms of secondary growth using Arabidopsis hypocotyl (Fig. 3).
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