Regulation of sulfur nutrition in wild-type and transgenic poplar over-expressing γ-glutamylcysteine synthetase in the cytosol as affected by atmospheric H2S
Regulation of sulfur nutrition in wild-type and transgenic poplar over-expressing γ-glutamylcysteine synthetase in the cytosol as affected by atmospheric H2S
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DOI：
10.1104/pp.124.1.461
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发表时间：
2000-09-01
期刊：
影响因子：
7.4
通讯作者：
Rennenberg, H
中科院分区：
文献类型：
--
作者：
Herschbach, C;van der Zalm, E;Rennenberg, H
本研究的目的是检验白杨，即硫酸盐的吸收是由需求驱动的控制，这种调节是由韧皮部运输谷胱甘肽作为一个芽到根的信号介导的。因此，硫营养在（a）在转基因白杨中的硫酸盐需求增加过表达γ-谷氨酰半胱氨酸（γ-EC）合成酶的细胞质和（B）在短期暴露于H2S的硫酸盐需求减少进行了研究。H2S叶片吸收增加半胱氨酸，γ-EC，谷胱甘肽浓度在叶，木质部汁液，韧皮部渗出物，和根，无论是在野生型和转基因白杨。观察到的硫酸盐木质部负荷减少后，H2S暴露的野生型白杨可以很好地解释了较高的谷胱甘肽浓度在韧皮部。在转基因白杨谷胱甘肽和γ-EC的浓度增加，不仅在叶，木质部汁液，根，但也在韧皮部分泌物中，无论H2S暴露。尽管增强韧皮部分配谷胱甘肽和其在根中的积累，硫酸盐吸收强烈增强。这一发现是矛盾的假设，谷胱甘肽分配在韧皮部减少硫酸盐的吸收和运输的拍摄。相关性分析提供了间接证据表明，硫酸盐与谷胱甘肽的比例在韧皮部可以控制硫酸盐的吸收和加载到木质部，无论是当硫酸盐的需求量增加，当它减少。
This study with poplar (Populus tremula x Populus alba) cuttings was aimed to test the hypothesis that sulfate uptake is regulated by demand-driven control and that this regulation is mediated by phloem-transported glutathione as a shoot-to-root signal. Therefore, sulfur nutrition was investigated at (a) enhanced sulfate demand in transgenic poplar over-expressing gamma-glutamylcysteine (gamma-EC) synthetase in the cytosol and (b) reduced sulfate demand during short-term exposure to H2S. H2S taken up by the leaves increased cysteine, gamma-EC, and glutathione concentrations in leaves, xylem sap, phloem exudate, and roots, both in wild-type and transgenic poplar. The observed reduced xylem loading of sulfate after H2S exposure of wild-type poplar could well be explained by a higher glutathione concentration in the phloem. In transgenic poplar increased concentrations of glutathione and gamma-EC were found not only in leaves, xylem sap, and roots but also in phloem exudate irrespective of H2S exposure. Despite enhanced phloem allocation of glutathione and its accumulation in the roots, sulfate uptake was strongly enhanced. This finding is contradictory to the hypothesis that glutathione allocated in the phloem reduces sulfate uptake and its transport to the shoot. Correlation analysis provided circumstantial evidence that the sulfate to glutathione ratio in the phloem may control sulfate uptake and loading into the xylem, both when the sulfate demand of the shoot is increased and when it is reduced.