Zonia Laura, Munnik Teun
Institute of Experimental Botany, Na Pernikarce 15, 160 00 Prague 6, Czech Republic.
Plant Physiol. 2004 Feb;134(2):813-23. doi: 10.1104/pp.103.029454. Epub 2004 Jan 22.
Pollen tube cell volume changes rapidly in response to perturbation of the extracellular osmotic potential. This report shows that specific phospholipid signals are differentially stimulated or attenuated during osmotic perturbations. Hypo-osmotic stress induces rapid increases in phosphatidic acid (PA). This response occurs starting at the addition of 25% (v/v) water to the pollen tube cultures and peaks at 100% (v/v) water. Increased levels of PA were detected within 30 s and reached maximum by 15 to 30 min after treatment. The pollen tube apical region undergoes a 46% increase in cell volume after addition of 100% water (v/v), and there is an average 7-fold increase in PA. This PA increase appears to be generated by phospholipase D because concurrent transphosphatidylation of n-butanol results in an average 8-fold increase in phosphatidylbutanol. Hypo-osmotic stress also induces an average 2-fold decrease in phosphatidylinositol phosphate; however, there are no detectable changes in the levels of phosphatidylinositol bisphosphates. In contrast, salt-induced hyperosmotic stress from 50 to 400 mm NaCl inhibits phospholipase D activity, reduces the levels of PA, and induces increases in the levels of phosphatidylinositol bisphosphate isomers. The pollen tube apical region undergoes a 41% decrease in cell volume at 400 mm NaCl, and there is an average 2-fold increase in phosphatidylinositol 3,5-bisphosphate and 1.4-fold increase in phosphatidylinositol 4,5-bisphosphate. The phosphatidylinositol 3,5-bisphosphate increase is detected within 30 s and reaches maximum by 15 to 30 min after treatment. In summary, these results demonstrate that hypo-osmotic versus hyperosmotic perturbation and the resultant cell swelling or shrinking differentially activate specific phospholipid signaling pathways in tobacco (Nicotiana tabacum) pollen tubes.
花粉管细胞体积会因细胞外渗透势的扰动而迅速变化。本报告表明，在渗透扰动期间，特定的磷脂信号会受到不同程度的刺激或减弱。低渗胁迫会诱导磷脂酸（PA）迅速增加。这种反应在向花粉管培养物中添加25%（v/v）水时开始出现，并在添加100%（v/v）水时达到峰值。在处理后30秒内检测到PA水平升高，并在15至30分钟后达到最大值。添加100%水（v/v）后，花粉管顶端区域的细胞体积增加了46%，PA平均增加了7倍。这种PA的增加似乎是由磷脂酶D产生的，因为正丁醇的同时转磷脂酰化导致磷脂酰丁醇平均增加了8倍。低渗胁迫还会导致磷脂酰肌醇磷酸平均减少2倍；然而，磷脂酰肌醇二磷酸的水平没有可检测到的变化。相比之下，50至400 mM NaCl引起的盐诱导高渗胁迫会抑制磷脂酶D的活性，降低PA的水平，并诱导磷脂酰肌醇二磷酸异构体水平的增加。在400 mM NaCl时，花粉管顶端区域的细胞体积减少了41%，磷脂酰肌醇3,5-二磷酸平均增加了2倍，磷脂酰肌醇4,5-二磷酸增加了1.4倍。在处理后30秒内检测到磷脂酰肌醇3,5-二磷酸的增加，并在15至30分钟后达到最大值。总之，这些结果表明，低渗与高渗扰动以及由此产生的细胞肿胀或收缩会在烟草（Nicotiana tabacum）花粉管中差异激活特定的磷脂信号通路。
