Nordström Anders, Tarkowski Petr, Tarkowska Danuse, Norbaek Rikke, Astot Crister, Dolezal Karel, Sandberg Göran
Umeå Plant Science Centre, Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden.
Proc Natl Acad Sci U S A. 2004 May 25;101(21):8039-44. doi: 10.1073/pnas.0402504101. Epub 2004 May 14.
One of the most long-lived models in plant science is the belief that the long-distance transport and ratio of two plant hormones, auxin and cytokinin, at the site of action control major developmental events such as apical dominance. We have used in vivo deuterium labeling and mass spectrometry to investigate the dynamics of homeostatic cross talk between the two plant hormones. Interestingly, auxin mediates a very rapid negative control of the cytokinin pool by mainly suppressing the biosynthesis via the isopentenyladenosine-5'-monophosphate-independent pathway. In contrast, the effect of cytokinin overproduction on the entire auxin pool in the plant was slower, indicating that this most likely is mediated through altered development. In addition, we were able to confirm that the lateral root meristems are likely to be the main sites of isopentenyladenosine-5'-monophosphate-dependent cytokinin synthesis, and that the aerial tissue of the plant surprisingly also was a significant source of cytokinin biosynthesis. Our demonstration of shoot-localized synthesis, together with data demonstrating that auxin imposes a very rapid regulation of cytokinin biosynthesis, illustrates that the two hormones can interact also on the metabolic level in controlling plant development, and that the aerial part of the plant has the capacity to synthesize its own cytokinin independent of long-range transport from the root system.
植物科学领域最具持久性的模型之一是,人们认为两种植物激素(生长素和细胞分裂素)在作用部位的长距离运输及比例控制着诸如顶端优势等主要发育事件。我们利用体内氘标记和质谱技术研究了这两种植物激素之间稳态相互作用的动态过程。有趣的是,生长素主要通过抑制经由不依赖于异戊烯基腺苷 - 5'- 单磷酸的途径的生物合成,对细胞分裂素库进行非常快速的负调控。相比之下,细胞分裂素过量产生对植物中整个生长素库的影响较慢,这表明这很可能是通过发育改变介导的。此外,我们能够证实侧根分生组织可能是依赖于异戊烯基腺苷 - 5'- 单磷酸的细胞分裂素合成的主要部位,而且植物的地上组织令人惊讶地也是细胞分裂素生物合成的重要来源。我们对地上部位合成的证明,以及生长素对细胞分裂素生物合成施加非常快速调控的数据表明,这两种激素在控制植物发育的代谢水平上也能相互作用,并且植物地上部分有能力独立于从根系的长距离运输来合成自身的细胞分裂素。