Department of Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Plant Physiol. 2010 Feb;152(2):736-46. doi: 10.1104/pp.109.150896. Epub 2009 Dec 9.
Oscillatory tip growth in pollen tubes depends on prodigious amounts of energy. We have tested the hypothesis that oscillations in the electron transport chain lead to growth oscillations in lily (Lilium formosanum). Using three respiratory inhibitors, oligomycin, antimycin A, and cyanide, we find that pollen tube growth is much less sensitive to respiratory inhibition than respiration is. All three block respiration at concentrations severalfold lower than necessary to inhibit growth. Mitochondrial NAD(P)H and potentiometric JC-1 fluorescence, employed as markers for electron transport chain activity, rise rapidly in response to oligomycin, as expected. Pollen tube growth stops for several minutes before resuming. Subsequent growth has a lower mean rate, but continues to oscillate, albeit with a longer period. NAD(P)H fluorescence no longer exhibits coherent oscillations, and mitochondria no longer congregate directly behind the apex: they distribute evenly throughout the cell. Postinhibition growth relies on aerobic fermentation for energy production as revealed by an increase in ethanol in the media. These data suggest that oscillatory growth depends not on a single oscillatory pacemaker but rather is an emergent property arising from a number of stable limit cycles.
花粉管的震荡式尖端生长依赖于巨大的能量供应。我们检验了一个假说，即电子传递链中的震荡会导致百合（Lilium formosanum）花粉管的生长震荡。我们使用三种呼吸抑制剂（寡霉素、抗霉素 A 和氰化物）发现，花粉管生长对呼吸抑制的敏感性远低于呼吸本身。这三种抑制剂在抑制生长所需浓度的几倍以下就会完全抑制呼吸。线粒体 NAD(P)H 和 JC-1 荧光强度（作为电子传递链活性的标志物）如预期的那样，在受到寡霉素刺激后迅速升高。花粉管生长停止几分钟后才恢复。随后的生长具有较低的平均速率，但仍在继续震荡，尽管周期较长。NAD(P)H 荧光不再表现出连贯的震荡，线粒体也不再直接聚集在尖端后面：它们在整个细胞中均匀分布。抑制后生长依赖于有氧发酵来产生能量，这可以通过培养基中乙醇的增加来证明。这些数据表明，震荡式生长不是依赖于单一的震荡节奏器，而是源自多个稳定的极限环的涌现特性。
