Non-structural carbohydrates and catalytic activities of sucrose metabolizing enzymes in trunks of two Juglans species and their role in heartwood formation
Non-structural carbohydrates and catalytic activities of sucrose metabolizing enzymes in trunks of two Juglans species and their role in heartwood formation
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DOI：
10.1515/hf.2001.022
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发表时间：
2001-01-01
期刊：
影响因子：
2.4
通讯作者：
Hampp, R
中科院分区：
文献类型：
--
作者：
Magel, E;Abdel-Latif, A;Hampp, R
研究了黑核桃和王核桃杂交种的树干中非结构碳水化合物、蔗糖合成和降解酶的存在及其与心材形成的相关性。淀粉和蔗糖的含量在最年轻的边材中最高，随着组织年龄的增加而降低，并且在心材中不存在。边材中单糖葡萄糖和果糖的含量较低，心材中不含果糖。杂交种树干边材心材边界处的葡萄糖短暂增加。然而，在黑胡桃木茎中，葡萄糖开始在过渡区内积聚，并在心材中达到相当多的量。核桃木的冷适应特点是可溶性糖的积累。蔗糖磷酸合酶（SPS，EC 2.4.1.14）速率的提高使得蔗糖形成成为可能。仲冬淀粉-糖的相互转化伴随着蔗糖合酶（SuSy，EC 2.4.1.13；黑胡桃）或酸性转化酶（EC 3.2.2.26；杂交）活性的增加。在正在形成心材的组织中，从夏末到初冬，蔗糖分解增强。蔗糖分解以酸性转化酶为主，蔗糖合酶的贡献较小。参与蔗糖裂解产物代谢的UDP-葡萄糖焦磷酸化酶(EC 2.7.7.9)的催化活性遵循这种季节性趋势，并且从夏末到初冬表现出较高的活性。这些数据进一步证明了早期提出的假设（Hauch 和 Magel，1998），即心材类黄酮的原位合成依赖于初级（蔗糖）和次级代谢之间的相互作用。然而，类黄酮仅占核桃心材的一小部分，而大部分心材酚类物质似乎来自酚类前体的转化。因此，这些最近的发现与早期的数据一起被视为存在不止一种类型的心材形成的证据。
In trunks of Juglans nigra and the hybrid J. major x J. regia the presence of non-structural carbohydrates, sucrose synthesizing and degrading enzymes, and their correlation with heartwood formation was investigated. Contents of starch and sucrose were highest in the youngest sapwood, decreased with increasing age of the tissue, and were absent in the heartwood. Pools of the monosaccharides glucose and fructose were low in the sapwood, and fructose was absent from the heartwood. Glucose transiently increased at the sapwood heartwood boundary in trunks of the hybrid. In black walnut stems, however, glucose started to accumulate within the transition zone and reached considerable amounts in the heartwood. Cold-adaptation in walnut wood was characterized by accumulation of soluble sugars. Sucrose formation was enabled by enhanced rates of sucrose-phosphate synthase (SPS, EC 2.4.1.14). Mid-winter starch-sugar interconversion was accompanied by increases in the activity of sucrose synthase (SuSy, EC 2.4.1.13; black walnut), or acid invertases (EC 3.2.2.26; hybrid). In the tissues under going heartwood formation, sucrose breakdown was enhanced from late summer until early winter. Sucrolysis was dominated by acid invertases with minor contribution of sucrose synthase. The catalytic activity of UDP-glucose pyrophosphorylase (EC 2.7.7.9), involved in the metabolization of the sucrose cleavage products, followed this seasonal trend and showed elevated activities from late summer until early winter. These data are further proof for the earlier made hypothesis (Hauch and Magel 1998) that the in situ synthesis of heartwood flavonoids relies on an interaction between primary (sucrose) and secondary metabolism. Flavonoids, however, constitute only a minor fraction in the heartwood of walnut and the bulk of heartwood phenolics seem to derive from transformation of phenolic precursors. Therefore, these recent findings together with earlier data are taken as evidence that mon than one type of heartwood formation exists.