Oxalate accumulation and regulation is independent of glycolate oxidase in rice leaves

• Published in: Journal of experimental botany Vol. 57; no. 9; pp. 1899 - 1908
• Main Authors: Xu, Hua-Wei, Ji, Xiu-Mei, He, Zheng-Hui, Shi, Wei-Ping, Zhu, Guo-Hui, Niu, Jian-Kang, Li, Bao-Sheng, Peng, Xin-Xiang
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.06.2006; Oxford Publishing Limited (England)
• Subjects: (s)-2-hydroxy-acid oxidase; Alcohol Oxidoreductases - metabolism; ammonium nitrogen; antisense DNA; biochemical pathways; Biological and medical sciences; Calcium; Catalysis; Cell physiology; chemical constituents of plants; DNA, Antisense; DNA, Plant; enzyme activity; estradiol; Fundamental and applied biological sciences. Psychology; Gene Expression; Glycolate oxidase; Glycolates; Glyoxylates; Kinetics; Leaves; messenger RNA; Molecular and cellular biology; nitrate nitrogen; Nitrates; Nitrogen - physiology; organic acids and salts; Oryza - genetics; Oryza - metabolism; Oryza sativa; oxalate accumulation; Oxalates; Oxalates - metabolism; oxalic acid; Oxidases; Plant Leaves - metabolism; Plants; Plants, Genetically Modified - metabolism; protein synthesis; Quaternary ammonium compounds; Research Paper; Rice; Signal transduction; transgenic plants; rice; Glycolate oxidase; oxalate accumulation; Fruit; Gene; Enzyme; (S)-2-Hydroxy-acid oxidase; Plant leaf; Transgenic plant; Oxidoreductases; Organic acids
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/erj131

Cellular oxalate, widely distributed in many plants, is implicated to play important roles in various functions and is also known to affect food qualities adversely in fruits and vegetables. How oxalate is regulated in plants is currently not well understood. Glycolate oxidase (GLO) has long been considered as an important player in oxalate accumulation in plants. To gain further insight into the biochemical and molecular mechanisms, the possible roles of GLO in the process were studied. Drastically different levels of oxalate could be achieved by treating rice with various nitrogen forms (nitrate versus ammonium). While nitrate stimulated oxalate accumulation, ammonium reduced its level. Such treatments resulted in similar pattern changes for some other related organic acids, such as glycolate, oxaloacetate, and malate. By feeding plants with exogenous glycolate it was possible almost completely to restore the ammonium-decreased oxalate level. Under the two treatments few differences were observed for GLO mRNA levels, protein levels, and in vitro activities. Both Km for glycolate/glyoxylate and Ki for oxalate remained almost the same for GLO purified from either nitrate- or ammonium-fed leaves. A further in vivo study, with transgenic plants carrying an estradiol-inducible GLO antisense gene, showed that, while the estradiol-induced antisense expression remarkably reduced both GLO protein levels and activities, oxalate levels were not significantly altered in the estradiol-treated transgenic plants. Taken together, it is suggested that oxalate accumulation and regulation is independent of GLO in rice leaves.