Koichi Suzuki - Insect Physiology, Insect Biotechnology - koichi@ Professor United Graduate School of Agricultural Sciences Strategic mechanism of biological systems for thermal energy - Molecular mechanism of overwintering dormancy in insect system -

I. Research achievements
Winter dormancy is a biological phenomenon that is extensively seen among organisms, from microorganisms to plants and mammals. My group has been studying the physiological molecular mechanisms of dormancy using insects as the subject.

Among the dormancy phenomenon of the great number of insects, we have focused on the unique biosystem of a Japanese wild silkworm (Antheraea yamamai), a large-sized experimental insect. A pre-larva (pharate first instar larva) of A. yamamai spends the winter in diapause/dormancy after its body is completely developed within the egg shell (pre-larval dormancy). The leaf beetle, Gastrophysa atrocyanea, is another unique insect of the Chrysomelidae family (Coleoptera), which feeds on dock weeds in hay fields, thus sometimes called a "biological exterminator." Adult individuals of G. atrocyanea spend 10 months each year in diapause/dormancy under the ground.

We identified a novel member of pentapeptide in the pre-larval stage of A. yamamai and found out that it functions as a cell proliferation suppressor. Also, we established an artificial hatching method for this species using imidazole compounds. From the leaf beetle, we identified a new peptide and its gene that shows physiological activity as N-type voltage-gated Ca2+ channel blocker and a function as a growth inhibitor for phytopathogenic fungi. These results and other information obtained on the function of the new peptide and the mechanism of artificial hatching are used to understand the mechanism of diapause and dormancy of insects and to develop their biotechnology.

II. Goals in the COE Program
Our focus will be on the relationship between the temperature and biomolecular responses of insects. We will analyze the universal molecular transformation of the signals for diapause awakening and reproduction, which are triggered by a long-term exposure to the cold temperatures in nature. We believe that the imidazole compound-binding proteins we have identified in the artificial hatching method for A. yamamai should be an effective tool to understand the mechanism that transforms the physical exposure to the low temperature into the biological molecular reactions. In addition, understanding the molecular-level strategy of G. atrocyanea to avoid the heat during the summer and low temperatures during the winter should show us the biological potential under harmful temperature stresses and give us suggestions for their development.

III. Related website
http://news7a1.atm.iwate-u.ac.jp/~insect/

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