Exogenous ornithine is an effective precursor and the δ-ornithine amino transferase pathway contributes to proline accumulation under high N recycling in salt-stressed cashew leaves
Exogenous ornithine is an effective precursor and the δ-ornithine amino transferase pathway contributes to proline accumulation under high N recycling in salt-stressed cashew leaves
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DOI：
10.1016/j.jplph.2011.08.001
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发表时间：
2012-01-01
影响因子：
4.3
通讯作者：
Gomes Silveira, Joaquim Albenisio
中科院分区：
文献类型：
--
作者：
Almeida da Rocha, Iza Marineves;Vitorello, Victor Alexandre;Gomes Silveira, Joaquim Albenisio
三角鸟氨酸氨基转移酶（OAT）途径在脯氨酸合成中的作用仍然存在争议，并在受盐胁迫的腰果植物叶片中进行了评估。研究了与脯氨酸合成有关的酶活性和代谢物浓度，以及外源鸟氨酸和谷氨酸诱导脯氨酸积累的能力。脯氨酸积累与OAT活性的相关性最好，增加了4倍，并且NADH氧化与OAT和δ(1)-吡啶-5-羧酸还原酶（P5CR）的活性相耦合，表明通过OAT/P5C合成脯氨酸的潜力。总的来说，GS的活动。GOGAT和氨化GDH在盐度下基本保持不变。P5CR的活性对NaCl没有反应，而δ(1)-吡咯-5-羧酸脱氢酶则受到盐度的显著抑制。我们认为，如果P5C从线粒体输出到细胞质是可能的，那么P5CR随后将其转化为脯氨酸可能是重要的。在一项时间过程实验中，脯氨酸积累与氨基酸代谢紊乱有关，氨、游离氨基酸、谷氨酰胺、精氨酸和鸟氨酸浓度的大幅增加表明了这一点。相反，谷氨酸浓度仅在前24小时内适度增加。外源饲喂鸟氨酸作为前体，可以非常有效地诱导完整植株和叶盘中脯氨酸的积累，其中脯氨酸浓度比谷氨酸饲喂或盐处理的植株高几倍。我们的数据表明，脯氨酸积累可能是盐诱导的N循环增加的结果，导致鸟氨酸和其他与脯氨酸合成和OAT活性有关的代谢物水平增加。在这种代谢环境下，OAT途径可能对盐胁迫腰果叶片脯氨酸积累有重要贡献。(C) 2011爱思唯尔有限公司版权所有。
The role of the delta-ornithine amino transferase (OAT) pathway in proline synthesis is still controversial and was assessed in leaves of cashew plants subjected to salinity. The activities of enzymes and the concentrations of metabolites involved in proline synthesis were examined in parallel with the capacity of exogenous ornithine and glutamate to induce proline accumulation. Proline accumulation was best correlated with OAT activity, which increased 4-fold and was paralleled by NADH oxidation coupled to the activities of OAT and Delta(1)-pyrroline-5-carboxylate reductase (P5CR), demonstrating the potential of proline synthesis via OAT/P5C. Overall, the activities of GS. GOGAT and aminating GDH remained practically unchanged under salinity. The activity of P5CR did not respond to NaCl whereas Delta(1)-pyrroline-5-carboxylate dehydrogenase was sharply repressed by salinity. We suggest that if the export of P5C from the mitochondria to the cytosol is possible, its subsequent conversion to proline by P5CR may be important. In a time-course experiment, proline accumulation was associated with disturbances in amino acid metabolism as indicated by large increases in the concentrations of ammonia, free amino acids, glutamine, arginine and ornithine. Conversely, glutamate concentrations increased moderately and only within the first 24 h. Exogenous feeding of ornithine as a precursor was very effective in inducing proline accumulation in intact plants and leaf discs, in which proline concentrations were several times higher than glutamate-fed or salt-treated plants. Our data suggest that proline accumulation might be a consequence of salt-induced increase in N recycling, resulting in increased levels of ornithine and other metabolites involved with proline synthesis and OAT activity. Under these metabolic circumstances the OAT pathway might contribute significantly to proline accumulation in salt-stressed cashew leaves. (C) 2011 Elsevier GmbH. All rights reserved.