Centro de Investigaciones Biológicas (CSIC), Madrid, Spain.
Plant Signal Behav. 2010 Feb;5(2):176-9. doi: 10.4161/psb.5.2.10966. Epub 2010 Feb 17.
Experiments performed in space have evidenced that, in root meristematic cells, the absence of gravity results in the uncoupling of cell growth and cell proliferation, two essential cellular functions that support plant growth and development, which are strictly coordinated under normal ground gravity conditions. In space, cell proliferation appears enhanced whereas cell growth is depleted. Since coordination of cell growth and proliferation is a major feature of meristematic cells, the observed uncoupling is a serious stress condition for these cells producing important alterations in the developmental pattern of the plant. Auxin plays a major role in these processes both by assuring the coupling of cell growth and proliferation under normal conditions and by exerting a decisive influence in the uncoupling under altered gravity conditions. Auxin is a mediator of the transduction of the gravitropic signal and its distribution in the root is altered subsequent to a change in the gravity conditions. This altered distribution may produce changes in the expression of specific growth coordinators leading to the alteration of cell cycle and protein synthesis. Therefore, available data indicate that the effects of altered gravity on cell growth and proliferation are the consequence of the transduction of the gravitropic signal perceived by columella cells, in the root tip.
在太空中进行的实验表明，在根分生组织细胞中，重力的缺失会导致细胞生长和细胞增殖的解耦，这是支持植物生长和发育的两个基本细胞功能，在正常地面重力条件下它们是严格协调的。在太空中，细胞增殖似乎增强了，而细胞生长则耗尽了。由于细胞生长和增殖的协调是分生组织细胞的主要特征，因此观察到的解耦是这些细胞的严重应激状态，会导致植物发育模式的重要改变。生长素在这些过程中起着主要作用，它通过在正常条件下确保细胞生长和增殖的偶联，并在改变重力条件下的解耦中发挥决定性影响。生长素是重力信号转导的介体，其在根中的分布在重力条件改变后发生改变。这种改变的分布可能会导致特定生长协调因子的表达发生变化，从而导致细胞周期和蛋白质合成的改变。因此，现有数据表明，改变重力对细胞生长和增殖的影响是根尖端柱形细胞感知到的重力信号转导的结果。
