Isolation of photocontrolled gibberellin 3beta-hydroxylase in lettuce seeds.

赤霉素介导了莴苣种子萌发的光诱导。对^3 H-GAs的投喂实验表明，光可激活GA合成活性的最后一步，即GA_3 β-羟基化<20>为GA_1。本研究旨在从莴苣种子中分离3-羟化酶并直接测定其活性变化，莴苣种子匀浆中含有大量酚类物质，酶活性较低，难以分离。此外，生菜种子供应短缺。从光抑制下胚轴生长的角度出发，从多个菜豆品种中筛选出一个矮生菜豆品种“绿色破折号”。白色光对下胚轴生长的抑制率在播种后5 ~ 10天内与年龄无关。光效应在0.4Wm ~ 2时接近饱和<-2>。当光照时间小于12小时时，抑制率与光照时间的对数呈线性关系，GA_3处理使受光抑制的下胚轴生长恢复到黑暗水平。而GA_3对暗培养的影响不大。另一方面，GA合成抑制剂的应用仅在黑暗中高度抑制生长。这些结果表明，光对赤霉素诱导下胚轴长度的影响是明显的。应用GA合成抑制剂所造成的生长抑制可通过应用GA_3而恢复。在此期间，光照苗完全恢复所需的GA_3浓度比黑暗苗高10倍左右。这些结果表明，光诱导下胚轴中GA含量降低，降低了下胚轴对GA的敏感性。

Gibberellin was mediated in the photoinduction of lettuce seeds germination. Feeding experiments of ^3H-GAs suggested that the final step of active GA synthesis, namely, 3beta-hydroxylation of GA_<20> to GA_1 was activated by light. The purpose of this research was isolate the 3 hydroxylase from lettuce seeds and to determine the change of activity directly.Enzyme activity of the lettuce seeds homogenate was too low to isolate it caused by the existence of plenty amount of phenolic compounds. Besides, the supply of lettuce seeds was shorted. Therefore, we must change the plant materials from lettuce to Phaseolus virgules.One dwarf variety of P. vergules named "Green dash" was selected from several variety on the viewpoint of photoinhibition of hypocotyl growth. Inhibition rate of hypocotyl growth by white light was age independent between 5 to 10 days after sowing. Effect of light was nearly saturated at 0.4Wm^<-2>. Inhibition rate was linear to the logarithm of irradiation period when it was shorter than 12 hr. Application of GA_3 recover the photoinhibited hypocotyl growth to the dark level. However, growth in the dark was little effected by GA_3. On the other hand, application of GA synthesis inhibitor highly suppress only the growth in the dark. These results suggested that the effect of light was visualize in the length of hypocotyl mediated by gibberellin. Growth inhibition obligated by the application of GA synthesis inhibitor was recovered by the application of GA_3. In this time, about 10 times higher concentration of GA_3 was required for the light grown seedling than dark grown one for full recovery. These results suggested that light induced the reduction of GA level in the hypocotyl and reduced the sensitivity of hypocotyl to GAs.