Analysis of Flowering Induced by L-Pipecolic Acid in Lemna

L-吡哌酸是从浮萍提取物中分离得到的一种诱花活性物质。随后的研究表明，L-吡喃甲酸对许多浮萍品系的开花都有一定的诱导作用。然而，L-吡喃甲酸诱导浮萍开花的机制仍有待确定。为了阐明L-吡啶甲酸诱导浮萍开花的机理，研究了L-吡喃甲酸的生物合成和代谢与浮萍开花的关系。此外，还对L-吡啶甲酸诱导的基因和蛋白质进行了分析，发现赖氨酸具有诱导浮萍开花的活性，并且赖氨酸分解代谢产物α-氨基己二酸的存在增强了赖氨酸对浮萍开花的影响。这些结果表明，浮萍的开花可能是由外源赖氨酸衍生的L-吡啶甲酸诱导的。氨基酸分析表明，外源赖氨酸可使L-吡啶甲酸的含量增加数倍。此外，我们还用氚标记的赖氨酸进行代谢研究，确证了赖氨酸转化为L-吡啶甲酸的能力。因此，本研究表明，赖氨酸转化为L-吡啶甲酸诱导浮萍开花。L-吡喃甲酸可通过添加该化合物诱导浮萍开花。利用该体系对L-吡啶甲酸诱导的基因和蛋白质进行了检测。L-吡喃甲酸处理使总核糖核酸有增加的趋势，但基因表达没有明显变化。此外，未发现L-吡啶甲酸诱导的特异性蛋白质。

Previosly L-Pipecolic acid was isolated as a flower-inducing substance from Lemna extracts. A subsequent study demonstrated that L-pipecolic acid is effective in inducing flowering of many strains of Lemna. The mechanism by which L-pipecolic acid induces flowering in Lemna remains, however, to be determined. In order to clarify the flowering mechanism induced by L-pipecolic acid in Lemna, biosynthesis and metabolism of L-pipecolic acid was investigated in relation to flowering. In addition, analysis of gene and protein specifically induced by L-pipecolic acid was carried out.Lysine was found to have flower-inducing activity in Lemna, and the effect of lysine on flowering was found to be enhanced in the presence of lysine catabolite, alpha-aminoadipic acid. These results suggested that the flowering of Lemna might be induced by L-pipecolic acid, derived from exogenously applied lysine. Amino-acid analysis indicated that the level of L-pipecolic acid increased several fold by exogenous application of lysine to the medium. In addition, the conversion of lysine to L-pipecolic acid was demonstrated definitively by metabolic study using deuterium labeled lysine. Thus, the present study indicates that conversion of lysine to L-pipecolic acid induces flowering of Lemna. L-Pipecolic acid can induce flowering of Lemna by the addition of this compound to the medium. Using this system, gene and protein induced by L-pipecolic acid were examined. Treatment of L-pipecolic acid tended to increase total RNA,however, no significant change of gene expression was found. Furthermore, no specific protein induced by L-pipecolic acid was found.