National Engineering Laboratory for Forest Tree Breeding, Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants of Ministry of Education, College of Biological Science and Technology, Beijing Forestry University, Beijing 100083, PR China.
J Exp Bot. 2013 Aug;64(11):3411-24. doi: 10.1093/jxb/ert186.
Bioactive gibberellins (GAs) are involved in many developmental aspects of the life cycle of plants, acting either directly or through interaction with other hormones. Accumulating evidence suggests that GAs have an important effect on root growth; however, there is currently little information on the specific regulatory mechanism of GAs during adventitious root development. A study was conducted on tobacco (Nicotiana tabacum) plants for altered rates of biosynthesis, catabolism, and GA signalling constitutively or in specific tissues using a transgenic approach. In the present study, PtGA20ox, PtGA2ox1, and PtGAI were overexpressed under the control of the 35S promoter, vascular cambium-specific promoter (LMX5), or root meristem-specific promoter (TobRB7), respectively. Evidence is provided that the precise localization of bioactive GA in the stem but not in the roots is required to regulate adventitious root development in tobacco. High levels of GA negatively regulate the early initiation step of root formation through interactions with auxin, while a proper and mobile GA signal is required for the emergence and subsequent long-term elongation of established primordia. The results demonstrated that GAs have an inhibitory effect on adventitious root formation but a stimulatory effect on root elongation.
生物活性赤霉素（GAs）参与植物生命周期的许多发育方面，直接或通过与其他激素相互作用发挥作用。越来越多的证据表明，GA 对根生长有重要影响；然而，目前关于 GA 在不定根发育过程中的具体调节机制的信息很少。本研究采用转基因方法，对烟草（Nicotiana tabacum）植物进行了改变生物合成、分解代谢和 GA 信号转导的速率的研究，这些改变是组成型的或在特定组织中进行的。在本研究中，PtGA20ox、PtGA2ox1 和 PtGAI 分别在 35S 启动子、血管形成层特异性启动子（LMX5）或根分生组织特异性启动子（TobRB7）的控制下过表达。有证据表明，生物活性 GA 在茎中的精确定位而不是在根中，是调节烟草不定根发育所必需的。GA 水平的升高通过与生长素的相互作用，负调控根形成的早期起始步骤，而适当和可移动的 GA 信号是已建立原基出现和随后的长期伸长所必需的。结果表明，GA 对不定根形成有抑制作用，但对根伸长有促进作用。
