Evidence for down-regulation of ethanolic fermentation and K+ effluxes in the coleoptile of rice seedlings during prolonged anoxia
Evidence for down-regulation of ethanolic fermentation and K+ effluxes in the coleoptile of rice seedlings during prolonged anoxia
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DOI：
10.1093/jexbot/52.360.1507
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发表时间：
2001-07-01
影响因子：
6.9
通讯作者：
Greenway, H
中科院分区：
文献类型：
--
作者：
Colmer, TD;Huang, SB;Greenway, H
乙醇发酵是耐缺氧水稻胚芽组织中主要的分解代谢途径，通过葡萄糖喂养在切除和“老化”的组织中进行操纵。经外源葡萄糖处理的胚芽在缺氧条件下存活了60 h，这可以从再曝气时根系和芽对K+和磷酸盐的吸收和生长的旺盛速率中得到证明。相比之下，没有外源性葡萄糖的胚芽组织在缺氧12小时后开始出现K+和磷酸盐的净损失，在缺氧60小时后重新通气时，这些损失没有完全恢复。乙醇产量(pmol g（-1) FW h(-1)）从缺氧前12小时的约7.5下降到48-60小时后的5或2.2，分别在有无外源葡萄糖的情况下。由于净葡萄糖摄取量为2.6 μ mol g(-1) FW h(-1)，缺氧菌体中碳水化合物浓度仅发生轻微变化。乙醇发酵，因此ATP的生产，可能已经下调了初始阶段的适应缺氧后，在外源葡萄糖的胚囊。据评估，这些缺氧的胚芽鞘对能量的维持需求比未生长的充气叶片组织低3.4-7.6倍。所需的能源消耗经济中，有一小部分来自离子输运的减少；缺氧使这些胚囊对K+和磷酸盐的净吸收减少了70-90%。在缺氧条件下，K+的外排比在有外源性葡萄糖的充气胚囊中低10倍。利用单向外流方程，估计缺氧时细胞膜对K+的通透性比充气时低17倍，可能是由于K+通道主要关闭。
Ethanolic fermentation, the predominant catabolic pathway in anoxia-tolerant rice coleoptiles, was manipulated in excised and 'aged' tissues via glucose feeding. Coleoptiles with exogenous glucose survived 60 h of anoxia, as evidenced by vigorous rates of K+ and phosphate not uptake and growth of roots and shoots when re-aerated. In contrast, coleoptiles without exogenous glucose showed net losses of K+ and phosphates starting 12 h after anoxia was imposed and these did not recover fully when re-aerated after 60 h of anoxia. Ethanol production (pmol g(-1) FW h(-1)) declined from about 7.5 during the first 12 h of anoxia to 5 or 2.2 after 48-60 h, in coleoptiles with or without exogenous glucose, respectively. Carbohydrate concentrations changed only slightly in anoxic coleoptiles with exogenous glucose due to net glucose uptake at 2.6 mu mol g(-1) FW h(-1). Ethanolic fermentation, and therefore ATP production, may have been down-regulated after an initial period of acclimation to anoxia in coleoptiles with exogenous glucose. Maintenance requirements for energy were assessed to be 3.4-7.6-fold lower in these anoxic coleoptiles than published estimates for non-growing aerated leaf tissues. A modest part of the required economy in energy consumption would have been derived from diminished ion transport; anoxia reduced K+ and phosphate net uptake by 70-90% in these coleoptiles. K+ efflux was 10-fold lower in anoxic than in aerated coleoptiles with exogenous glucose. Using the unidirectional efflux equation, the membrane permeability to K+ was estimated to be 17-fold lower in anoxic than in aerated coleoptiles, presumably due to predominantly closed K+ channels.