Effect of hexokinase activity on tomato root metabolism during prolonged hypoxia
Effect of hexokinase activity on tomato root metabolism during prolonged hypoxia
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DOI：
10.1111/j.1365-3040.2007.01640.x
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发表时间：
2007-04-01
影响因子：
7.3
通讯作者：
Brouquisse, Renaud
中科院分区：
文献类型：
--
作者：
Gharbi, Imene;Ricard, Berenice;Brouquisse, Renaud
番茄（Solanum lycopersicum）根对缺氧的耐受性依赖于蔗糖和蔗糖合成酶的诱导。与玉米相反，根己糖激酶（HXK）活性在缺氧过程中没有增加，葡萄糖不能维持糖酵解流量。在本文中，我们问是否会改变在根中的缺氧代谢的转基因番茄植物过表达的植物（拟南芥）或酵母（酿酒酵母）HXK和这种修改是否可能与改善能量代谢，从而根耐缺氧。水培生长的番茄植株，其芽始终保持在空气中，通过停止空气鼓泡进行7天的低氧处理。一个组合的技术，包括H-1-核磁共振光谱，RT-PCR和酶分析被用来获得一个广泛的图片缺氧根代谢。在常氧条件下，HXK的过表达只在AtHXK 1转基因植物的根中导致更高的ADP和AMP水平。在低氧处理过程中，在水培槽中的氧气水平迅速下降到5 kPa内的第一个2 d，然后在整个7 d的实验中保持在5 kPa。在水面以下5和20厘米处的氧气水平相似。腺苷酸能量状态的下降后2 d的低氧处理，进一步减少7 d的非转基因（WT）和ScHXK 2的根，但不是在AtHXK 1转基因植物。与AtHXK 1根相比，WT和ScHXK 2根中蔗糖合成酶活性在低氧处理7 d时增加到100%以上。WT和转基因植物之间的差异进行了讨论，相对于低（缺氧），但不是零（缺氧）氧的代谢反应。
Hypoxically induced tolerance to anoxia in roots of tomato (Solanum lycopersicum) was previously shown to depend on sucrose and the induction of sucrose synthase. In contrast to maize, root hexokinase (HXK) activities did not increase during hypoxia and glucose was unable to sustain glycolytic flux under anoxia. In this paper, we asked whether hypoxic metabolism in roots would be altered in transgenic tomato plants overexpressing either a plant (Arabidopsis) or a yeast (Saccharomyces cerevisiae) HXK and whether such modifications could be related to improved energy metabolism and consequently root tolerance under anoxia. Tomato plants grown hydroponically with shoots always maintained in air were submitted to a 7 d hypoxic treatment applied by stopping air bubbling. A combination of techniques including H-1-nuclear magnetic resonance spectroscopy, RT-PCR and enzyme analyses was used to obtain a broad picture of hypoxic root metabolism. In normoxic conditions, HXK overexpression resulted in higher ADP and AMP levels only in roots of AtHXK1 transgenic plants. During hypoxic treatment, oxygen levels in the hydroponic tank decreased rapidly to 5 kPa within the first 2 d and then remained at 5 kPa throughout the 7 d experiment. Oxygen levels were similar at 5 and 20 cm below the water surface. A decline of the adenylate energy status was observed after 2 d of hypoxic treatment, with a further decrease by 7 d in roots of non-transgenic (WT) and ScHXK2, but not in AtHXK1 transgenic plants. Sucrose synthase activity increased to comparably higher levels at 7 d of hypoxic treatment in WT and ScHXK2 compared with AtHXK1 roots. Differences between WT and the transgenic plants are discussed with respect to the metabolic response to low (hypoxia) but not zero (anoxia) oxygen.