Xia J H, Saglio P
Station de Physiologie Végétale, INRA, Centre de Recherches de Bordeaux, B.P. 81, 33883 Villenave d'Ornon Cedex, France.
Plant Physiol. 1990 Jun;93(2):453-9. doi: 10.1104/pp.93.2.453.
The relationship between changes in H(+) flux and sugar transport in maize Zea mays L. DEA root tips have been investigated using two methods for controlling the cellular nucleotide level: (a) incubation in the presence of a glucose analog, the 2-deoxyglucose, which decreased the ATP level to less than 15% of its initial value within 60 minutes without changing the ADP and AMP levels; (b) an hypoxic treatment which also decreased the ATP level but with a concomitant rise in ADP and AMP. In both cases the rate of hexose transport was not modified until ATP had dropped to 70% of its initial value; then it decreased with the cellular ATP level. The residual uptake rate at very low ATP concentrations still represented 50% of the maximum rate with the dGlc treatment but only the diffusion rate in anoxia. H(+) efflux was abolished in anoxia but not by the 2-deoxyglucose treatment, in spite of a lower cellular ATP concentration. Our results are consistent with an inhibition of H(+)-ATPase activity in anoxia by the high levels of cellular ADP and AMP, and provide in vivo evidence that sugar uptake is dependent upon the proton motive force rather than cellular ATP concentration. The absence of stimulation of H(+) extrusion by ferricyanide in either normoxic or hypoxic conditions suggests that a redox system does not appear to contribute to H(+) secretion under the conditions of this investigation.
利用两种控制细胞核苷酸水平的方法，研究了玉米（Zea mays L.）根尖端中H⁺通量变化与糖转运之间的关系：（a）在葡萄糖类似物2-脱氧葡萄糖存在下孵育，该物质在60分钟内将ATP水平降至初始值的15%以下，而不改变ADP和AMP水平；（b）缺氧处理，该处理也降低了ATP水平，但同时伴随着ADP和AMP的升高。在这两种情况下，直到ATP降至初始值的70%之前，己糖转运速率都没有改变；然后它随着细胞ATP水平的下降而降低。在极低ATP浓度下的残余摄取率，在dGlc处理中仍占最大速率的50%，但在缺氧条件下仅为扩散速率。尽管细胞ATP浓度较低，但缺氧时H⁺外流被消除，而2-脱氧葡萄糖处理则没有。我们的结果与缺氧时细胞内高水平的ADP和AMP对H⁺-ATPase活性的抑制作用一致，并提供了体内证据表明糖摄取依赖于质子动力而非细胞ATP浓度。在常氧或缺氧条件下，铁氰化物均未刺激H⁺外流，这表明在本研究条件下，氧化还原系统似乎对H⁺分泌没有贡献。
