Carle SA, Bates GW, Shannon TA
Department of Biological Science, Florida State University, Tallahassee, FL 32306-3015, USA
J Plant Growth Regul. 1998 Dec;17(4):221-230. doi: 10.1007/pl00007038.
The roles of auxin and cytokinin in cell cycle reactivation were studied during the first 48 h of culture of mesophyll protoplasts of Nicotiana tabacum. Using hormone delay and withdrawal studies we found that auxin was required by 0-4 h of culture, whereas cytokinin was not required until hour 10-12, which is 6-10 h before S phase. Cycloheximide blocks division, indicating that protein synthesis is required. In an effort to detect a molecular response to either hormone, we examined the expression of the cell cycle marker, cdc2. Cdc2 expression was detected by 12 h of culture, coincident with the timing of the cytokinin requirement and well before the entry into S. However, cdc2 was partially induced by either auxin or cytokinin alone, suggesting that cdc2 expression is not the primary target of either hormone. Our hormone delay experiments suggest that there are separate signal transduction pathways leading from auxin and from cytokinin to reactivation of the cell cycle and that these pathways converge before S. The underlying mechanisms for these distinct pathways remain to be elucidated. Key Words. Auxin-Cytokinin-Tobacco-Protoplast-Development-cdc2
在烟草叶肉原生质体培养的最初48小时内，研究了生长素和细胞分裂素在细胞周期重新激活中的作用。通过激素延迟和撤除实验，我们发现培养0 - 4小时需要生长素，而直到培养10 - 12小时才需要细胞分裂素，此时距离S期还有6 - 10小时。放线菌酮可阻断细胞分裂，这表明蛋白质合成是必需的。为了检测对这两种激素的分子反应，我们检测了细胞周期标记物cdc2的表达。培养12小时时检测到cdc2的表达，这与细胞分裂素需求的时间一致，且远在进入S期之前。然而，单独使用生长素或细胞分裂素均可部分诱导cdc2，这表明cdc2的表达不是这两种激素的主要作用靶点。我们的激素延迟实验表明，存在从生长素和细胞分裂素到细胞周期重新激活的独立信号转导途径，且这些途径在S期之前汇聚。这些不同途径的潜在机制仍有待阐明。关键词：生长素 - 细胞分裂素 - 烟草 - 原生质体 - 发育 - cdc2
