Dewitte W, Chiappetta A, Azmi A, Witters E, Strnad M, Rembur J, Noin M, Chriqui D
Laboratory for Plant Biochemistry and Physiology, Department of Biology, University of Antwerp, B-2610 Antwerp, Belgium (W.D., E.W., H.V.O.).
Plant Physiol. 1999 Jan;119(1):111-22. doi: 10.1104/pp.119.1.111.
This study considered cytokinin distribution in tobacco (Nicotiana tabacum L.) shoot apices in distinct phases of development using immunocytochemistry and quantitative tandem mass spectrometry. In contrast to vegetative apices and flower buds, we detected no free cytokinin bases (zeatin, dihydrozeatin, or isopentenyladenine) in prefloral transition apices. We also observed a 3-fold decrease in the content of cytokinin ribosides (zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine) during this transition phase. The group concluded that organ formation (e.g. leaves and flowers) is characterized by enhanced cytokinin content, in contrast to the very low endogenous cytokinin levels found in prefloral transition apices, which showed no organogenesis. The immunocytochemical analyses revealed a differing intracellular localization of the cytokinin bases. Dihydrozeatin and isopentenyladenine were mainly cytoplasmic and perinuclear, whereas zeatin showed a clear-cut nuclear labeling. To our knowledge, this is the first time that this phenomenon has been reported. Cytokinins do not seem to act as positive effectors in the prefloral transition phase in tobacco shoot apices. Furthermore, the differences in distribution at the cellular level may be indicative of a specific physiological role of zeatin in nuclear processes.
本研究利用免疫细胞化学和定量串联质谱法，考察了细胞分裂素在烟草（Nicotiana tabacum L.）茎尖不同发育阶段的分布情况。与营养顶端和花芽不同，我们在花前过渡顶端未检测到游离细胞分裂素碱基（玉米素、二氢玉米素或异戊烯基腺嘌呤）。我们还观察到在这个过渡阶段，细胞分裂素核糖苷（玉米素核糖苷、二氢玉米素核糖苷和异戊烯基腺苷）的含量下降了3倍。该研究团队得出结论，与花前过渡顶端极低的内源性细胞分裂素水平（此阶段无器官发生）相反，器官形成（如叶片和花朵）的特征是细胞分裂素含量增加。免疫细胞化学分析揭示了细胞分裂素碱基在细胞内的定位不同。二氢玉米素和异戊烯基腺嘌呤主要位于细胞质和核周，而玉米素则显示出明显的核标记。据我们所知，这是首次报道这种现象。在烟草茎尖的花前过渡阶段，细胞分裂素似乎并非起积极作用的因子。此外，细胞水平上分布的差异可能表明玉米素在核过程中具有特定的生理作用。
