P-31 植物の運動・光屈性に関わる鍵化学物質の構造と作用機構(ポスター発表の部)

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The phenomenon of plant seedlings bending toward light, to optimize the exposure of their photosynthetic organs, is called "phototropism". We have hitherto reported evidence that the differential flank growth that causes phototoropic curvature is regulated by a local gradient induced at the site of illumination, of blue light-induced growth inhibitors interfering with the action of evenly distributed auxin (Bruinsma-Hasegawa theory, 1990). To date, different plant species turn out to produce different and very specific growth inhibitors as candidates for phototropism-regulating substances. In this study, we report a role of inhibitors in the phototropism of Zea mays L., and structures of blue light-induced growth inhibitors from Helianthus annuus L. and Arabidopsis thaliana. We have already isolated two photo-induced growth inhibitory substances related to phototropism, DIMBOA and MBOA from maize (Z. mays L.) coleoptiles. β-Glucosidase inhibitor (TG) treatment caused a pronounced decrease in the phototropic curvature of Z. mays. A significant decrease in DIMBOA and MBOA levels with TG was occurred in the illuminated halves of the coleoptiles. Blue light promoted the accumulation of H_2O_2 in the illuminated sides and DIMBOA application induced the accumulation of H_2O_2 in the applied halves. β-Glucosidase transcriptional level was transiently up-regulated in the illuminated halves in response to blue light. A new potent growth inhibitor, helian, was isolated from blue light-illuminated sunflower (H. annuus L.) hypocotyls and the structure was determined by 2D NMR, MS, and chemical means. Helian showed plant growth-inhibitory activity at 1.2×10^<-5>M. The amount of helian was higher in the illuminated halves than in the shaded ones in phototropically stimulated sunflower hypocotyls. Using the wild-type and the nph3-101 mutant of A. thaliana that shows no phototropic response, we compared endogenous chemical substances in phototropically stimulated whole hypocotyls and the dark controls. From light-grown wild-type hypocotyls an inhibitor was isolated and identified as indole-3-acetonitrile (IAN). The IAN concentration in the phototropically stimulated wild-type hypocotyls was about 3 times larger than in the dark-control. However its content in the mutant hypocotyls did not change. IAN inhibited the hypocotyls growth of the nph3-101 to the same extent as in the wild-type. Finally, the plausible mechanism of phototropism in higher plants is described in Figure 9.
天然有機化合物討論会の論文
2006-09-15

P-31 植物の運動・光屈性に関わる鍵化学物質の構造と作用機構(ポスター発表の部)

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