L-ascorbic acid and L-galactose are sources for oxalic acid and calcium oxalate in Pistia stratiotes
L-ascorbic acid and L-galactose are sources for oxalic acid and calcium oxalate in Pistia stratiotes
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DOI：
10.1016/s0031-9422(99)00448-3
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发表时间：
2000-02-01
期刊：
影响因子：
3.8
通讯作者：
Franceschi, VR
中科院分区：
文献类型：
--
作者：
Keates, SE;Tarlyn, NM;Franceschi, VR
无菌水浮莲用[C-14]草酸、L-[1-C-14]抗坏血酸、L-[6-C-14]抗坏血酸、D-[1-C-14]异抗坏血酸、L-[1-C-14]半乳糖或[1-C-14]乙醇酸盐脉冲追踪标记植物。比较了标记植物中L-抗坏血酸（阿萨）、游离草酸（OxA）和草酸钙（CaOx）的比放射性。将叶组织样品固定用于显微放射自显影，并通过共聚焦显微镜检查。结果证明了阿萨作为OxA的前体及其结晶沉积产物CaOx在P. stratiotes的异细胞中的生物合成作用，并支持了惠勒、Jones和Smirnoff（惠勒，G.L.，琼斯硕士，Br Smirnoff，N.（1998年）。高等植物维生素C的生物合成途径。Nature，393，365-369），L-半乳糖是植物中D-葡萄糖转化为阿萨的关键中间体。D-[1-C-14]异抗坏血酸（阿萨的一种非对映体类似物）也被层状原杆菌用作OxA及其钙盐沉积产物在异细胞中的前体。标记的OxA在异细胞中迅速掺入CaOx，但显微放射自显影显示，OxA中的碳也显著掺入生长细胞的其他组分中，这与OxA是相对稳定的代谢终产物的教条相反。乙醇酸盐是合成OxA和CaOx形成的不良底物，进一步确立了阿萨作为合成OxA的直接前体，用于晶体异细胞中的钙沉淀。(C)2000爱思唯尔科技有限公司版权所有。
Axenic Pistia stratiotes L. plants were pulse-chase labeled with [C-14]oxalic acid, L-[1-C-14]ascorbic acid, L-[6-C-14]ascorbic acid, D-[1-C-14]erythorbic acid, L-[1-C-14]galactose, or [1-C-14]glycolate. Specific radioactivities of L-ascorbic acid (AsA), free oxalic acid (OxA) and calcium oxalate (CaOx) in labeled plants were compared. Samples of leaf tissue were fixed for microautoradiography and examined by confocal microscopy. Results demonstrate a biosynthetic role for AsA as precursor of OxA and its crystalline deposition product, CaOx, in idioblast cells of P. stratiotes and support the recent discovery of Wheeler, Jones and Smirnoff (Wheeler, G.L., Jones M.A., Br Smirnoff, N. (1998). The biosynthetic pathway of Vitamin C in higher plants. Nature, 393, 365-369) that L-galactose is a key intermediate in the conversion of D-glucose to AsA in plants. D-[1-C-14]Erythorbic acid (a diastereomeric analog of AsA) is utilized also by P. stratiotes as a precursor of OxA and its calcium salt deposition product in idioblasts. Labeled OxA is rapidly incorporated into CaOx in idioblasts, but microautoradiography shows there is also significant incorporation of carbon from OxA into other components of growing cells, contrary to the dogma that OxA is a relatively stable end product of metabolism. Glycolate is a poor substrate for synthesis of OxA and CaOx formation, further establishing AsA as the immediate precursor in the synthesis of OxA used for calcium precipitation in crystal idioblasts. (C) 2000 Elsevier Science Ltd. All rights reserved.