Enhanced cytosolic NADP-ME2 activity in A-thaliana affects plant development, stress tolerance and specific diurnal and nocturnal cellular processes
Enhanced cytosolic NADP-ME2 activity in A-thaliana affects plant development, stress tolerance and specific diurnal and nocturnal cellular processes
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DOI：
10.1016/j.plantsci.2015.09.015
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发表时间：
2015-11-01
期刊：
影响因子：
5.2
通讯作者：
Gerrard Wheeler, Mariel C.
中科院分区：
文献类型：
--
作者：
Badia, Mariana B.;Arias, Cintia L.;Gerrard Wheeler, Mariel C.
拟南芥具有四种NADP依赖的苹果酸酶（NADP-ME 1-4）用于可逆的苹果酸脱羧，NADP-ME 2是唯一的胞质异构体，其广泛表达并负责大部分总活性。在这项工作中，我们进一步研究了它的生理功能，通过表征拟南芥植物组成型过表达NADP-ME 2。与野生型相比，这些植物表现出减少莲座丛和根的大小，延迟开花时间和增加对甘露醇和聚乙二醇的敏感性。NADP-ME 2活性的增加导致其他ME和苹果酸脱氢酶亚型的表达减少，并产生氧化还原失衡，其特征与分析当天的时间点相反。在正常生长条件下，过表达的植物也呈现出较高的C-4有机酸和糖含量。然而，与野生型相比，这些代谢物在过表达植物中的积累在渗透胁迫暴露后基本上不太明显。此外，在转基因植物中观察到较低水平的几种氨基酸和植物保护剂化合物。因此，NADP-ME 2表达的获得在A. thaliana，反映了这种酶及其底物和产物在植物体内平衡中的相关性。(C)2015爱思唯尔爱尔兰有限公司版权所有。
Arabidopsis thaliana has four NADP-dependent malic enzymes (NADP-ME 1-4) for reversible malate decarboxylation, with NADP-ME2 being the only cytosolic isoform ubiquitously expressed and responsible for most of the total activity. In this work, we further investigated its physiological function by characterizing Arabidopsis plants over-expressing NADP-ME2 constitutively. In comparison to wild type, these plants exhibited reduced rosette and root sizes, delayed flowering time and increased sensitivity to mannitol and polyethylene glycol. The increased NADP-ME2 activity led to a decreased expression of other ME and malate dehydrogenase isoforms and generated a redox imbalance with opposite characteristics depending on the time point of the day analyzed. The over-expressing plants also presented a higher content of C-4 organic acids and sugars under normal growth conditions. However, the accumulation of these metabolites in the over-expressing plants was substantially less pronounced after osmotic stress exposure compared to wild type. Also, a lower level of several amino acids and osmoprotector compounds was observed in transgenic plants. Thus, the gain of NADP-ME2 expression has profound consequences in the modulation of primary metabolism in A. thaliana, which reflect the relevance of this enzyme and its substrates and products in plant homeostasis. (C) 2015 Elsevier Ireland Ltd. All rights reserved.