Phloem Import and Storage Metabolism Are Highly Coordinated by the Low Oxygen Concentrations within Developing Wheat Seeds1
Phloem Import and Storage Metabolism Are Highly Coordinated by the Low Oxygen Concentrations within Developing Wheat Seeds1
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DOI：
10.1104/pp.104.040980
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发表时间：
2004-07
期刊：
影响因子：
7.4
通讯作者：
Joost T. van Dongen;G. Roeb;M. Dautzenberg;A. Froehlich;Hélène Vigeolas;P. Minchin;P. Geigenberger
中科院分区：
文献类型：
--
作者：
Joost T. van Dongen;G. Roeb;M. Dautzenberg;A. Froehlich;Hélène Vigeolas;P. Minchin;P. Geigenberger
研究了小麦种子内氧浓度对贮藏代谢的影响及其与韧皮部营养物质输入的关系。在环境氧（21%）下发育的小麦种子被发现是缺氧的（2.1%）。通过降低或增加外部氧浓度来改变氧供应引起内部氧张力的平行变化。然而，内部浓度的降低比例小于外部氧的降低。这表明，减少氧气供应诱导短期适应性反应，以减少种子的耗氧量。当外部氧减少到8%时，内部氧减少到约0.5%，导致通过呼吸产生的能量减少。相反，增加外部氧浓度高于环境水平增加了氧含量以及种子的能量状态，表明在正常条件下，氧气供应强烈限制发育中的小麦种子的能量代谢。种子贮藏代谢的中间代谢产物没有受到实质性的影响时，氧气增加或减少。然而，在低于环境的外部氧浓度（8%）的碳到淀粉和蛋白质的代谢通量，通过注射14 C-Suc到种子中，分别减少了17%和32%，而没有显着的效果，观察到在超环境（40%）氧。所观察到的减少生物合成通量的存储化合物的建议是一个适应性反应的一部分，以减少能源消耗，防止过量的氧气消耗时，氧气供应是有限的。韧皮部运输向耳朵暴露于低（8%）氧气显着减少1小时内，而暴露耳朵高氧气（40%）没有显着影响。这与同化物的分布已经通过从植物去除较低的源叶而改变的情况形成对比，导致较少的同化物运输到穗，有利于运输到植物的较低部分。在这些条件下，有两个强烈竞争的水槽，高氧（40%）确实导致韧皮部运输到穗的强烈增加。结果表明，在小麦种子发育过程中，库代谢受低氧浓度的影响，决定了同化物通过韧皮部的输入速率。
We studied the influence of the internal oxygen concentration in seeds of wheat (Triticum aestivum) on storage metabolism and its relation to phloem import of nutrients. Wheat seeds that were developing at ambient oxygen (21%) were found to be hypoxic (2.1%). Altering the oxygen supply by decreasing or increasing the external oxygen concentration induced parallel changes in the internal oxygen tension. However, the decrease in internal concentration was proportionally less than the reduction in external oxygen. This indicates that decreasing the oxygen supply induces short-term adaptive responses to reduce oxygen consumption of the seeds. When external oxygen was decreased to 8%, internal oxygen decreased to approximately 0.5% leading to a decrease in energy production via respiration. Conversely, increasing the external oxygen concentration above ambient levels increased the oxygen content as well as the energy status of the seeds, indicating that under normal conditions the oxygen supply is strongly limiting for energy metabolism in developing wheat seeds. The intermediate metabolites of seed storage metabolism were not substantially affected when oxygen was either increased or decreased. However, at subambient external oxygen concentrations (8%) the metabolic flux of carbon into starch and protein, measured by injecting 14C-Suc into the seeds, was reduced by 17% and 32%, respectively, whereas no significant effect was observed at superambient (40%) oxygen. The observed decrease in biosynthetic fluxes to storage compounds is suggested to be part of an adaptive response to reduce energy consumption preventing excessive oxygen consumption when oxygen supply is limited. Phloem transport toward ears exposed to low (8%) oxygen was significantly reduced within 1 h, whereas exposing ears to elevated oxygen (40%) had no significant effect. This contrasts with the situation where the distribution of assimilates has been modified by removing the lower source leaves from the plant, resulting in less assimilates transported to the ear in favor of transport to the lower parts of the plant. Under these conditions, with two strongly competing sinks, elevated oxygen (40%) did lead to a strong increase in phloem transport to the ear. The results show that sink metabolism is affected by the prevailing low oxygen concentrations in developing wheat seeds, determining the import rate of assimilates via the phloem.