Changes in carbohydrate levels and their metabolic enzymes in leaves, phloem sap and mesocarp during cucumber (Cucumis sativus L.) fruit development
Changes in carbohydrate levels and their metabolic enzymes in leaves, phloem sap and mesocarp during cucumber (Cucumis sativus L.) fruit development
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DOI：
10.1016/j.scienta.2009.01.023
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发表时间：
2009-06-17
影响因子：
4.3
通讯作者：
Zhang, Zhen-Xian
中科院分区：
文献类型：
--
作者：
Hu, Li-Ping;Meng, Fan-Zhen;Zhang, Zhen-Xian
在黄瓜（Cucumis sativus L.）果实发育过程中，从开花前2天到开花后20天，对叶片（源）、韧皮部汁液（流）和中果皮组织（库）中的碳水化合物水平和代谢酶活性进行了检测。在所有三个取样器官中，总糖水平都有所增加，而随着果实发育，叶片和中果皮组织中的淀粉水平下降。葡萄糖和果糖是成熟叶片中可溶性糖库的主要成分。水苏糖是韧皮部汁液提取物中最重要的成分，其次是蔗糖和棉子糖。然而，中果皮组织中积累的主要糖类是葡萄糖和果糖，而不是水苏糖或蔗糖。叶片中蔗糖合成酶（蔗糖磷酸合成酶加上合成方向的蔗糖合酶）的活性超过了蔗糖降解酶（酸性转化酶、中性转化酶加上降解方向的蔗糖合酶）的活性，这可能导致用于棉子糖和水苏糖生物合成的蔗糖库。虽然碱性α - 半乳糖苷酶I型活性下降，但水苏糖合酶活性在开花后迅速增加，直到12天后才开始下降。中果皮组织中蔗糖降解酶的活性总是远高于蔗糖合成酶的活性。因此，中果皮组织中不会发生蔗糖积累。在中果皮组织中，水苏糖合酶活性稳定下降，碱性α - 半乳糖苷酶I型活性在下降之前有适度增加。还讨论了可溶性糖水平与相关酶活性之间的关系。（c）2009爱思唯尔有限公司。保留所有权利。
Levels of carbohydrates and activities of metabolic enzymes were examined in leaves (source), phloem sap (flow) and mesocarp tissues (sink) in the course Of cucumber (Cucumis sativus L.) fruit development, from 2 days before anthesis to 20 days after anthesis. While total sugar levels increased in all the three sampling organs, starch levels declined in leaves and mesocarp tissues as fruit development progressed. Glucose and fructose were the primary contributors to the soluble sugar pools in mature leaves. Stachyose was found as the most important component of the phloem sap extracts, followed by sucrose and raffinose. However, the primary sugars accumulated in mesocarp tissues were glucose and fructose, not stacliyose or sucrose. Activities of sucrose synthesizing enzymes (sucrose phosphate synthase Plus sucrose synthase in the synthesizing direction) exceeded that of sucrose degrading enzymes (acid invertase, neutral invertase plus sucrose synthase in the degrading direction) in leaves, which might cause a Sucrose pool utilized in raffinose and stachyose biosynthesis. While alkaline a-galactosidase form I activity declined, stachyose synthase activity showed a rapid increase until 12 days after anthesis and only subsequently decreased in leaves. Activities of sucrose degrading enzymes were always much higher than that of sucrose synthesizing enzymes in mesocarp tissues. Thus, sucrose accumulation could not occur in mesocarp tissues. While stachyose synthase activity steadily decreased, alkaline a-galactosidase form I activity showed a moderate increase before decrease in mesocarp tissues. The relationship between levels of soluble sugars and activities of relative enzymes was also discussed. (c) 2009 Elsevier B.V. All rights reserved.