Centro de Engenharia Biológica, Departamento de Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal.
Physiol Plant. 2009 Dec;137(4):485-97. doi: 10.1111/j.1399-3054.2009.01250.x. Epub 2009 May 5.
Biotic and abiotic stresses can lead to modifications in the lipid composition of cell membranes. Although mitochondria appear to be implicated in stress responses, little is known about the membrane lipid changes that occur in these organelles in plants. Besides cytochrome c oxidase, plant mitochondria have an alternative oxidase (AOX) that accepts electrons directly from ubiquinol, dissipating energy as heat. AOX upregulation occurs under a variety of stresses and its induction by salicylic acid (SA) has been observed in different plant species. AOX was also suggested to be used as a functional marker for cell reprogramming under stress. In the present study, we have used etiolated soybean (Glycine max (L.) Merr. cv Cresir) seedlings to study the effects of SA treatment on the lipid composition and the respiratory properties of hypocotyl mitochondria. AOX expression was studied in detail, as a reporter protein, to evaluate whether modifications in mitochondrial energy metabolism were occurring. In mitochondria extracted from SA-treated seedlings, AOX capacity and protein contents increased. Both AOX1 and AOX2b transcripts accumulated in response to SA, but with different kinetics. A reduction in external NADH oxidation capacity was observed, whereas succinate respiration remained unchanged. The phospholipid composition of mitochondria remained similar in control and SA-treated plants, but a reduction in the relative amount of linolenic acid was observed in phosphatidylcholine, phosphatidylethanolamine and cardiolipin. The possible causes of the fatty acid modifications observed, and the implications for mitochondrial metabolism are discussed.
生物和非生物胁迫会导致细胞膜脂质组成发生变化。尽管线粒体似乎与应激反应有关，但对于植物中线粒体中发生的膜脂变化知之甚少。除细胞色素 c 氧化酶外，植物线粒体还具有一种替代氧化酶（AOX），它可以直接从泛醌接受电子，将能量以热量的形式耗散。AOX 的上调发生在多种胁迫下，并且在不同的植物物种中已经观察到水杨酸（SA）诱导其诱导。AOX 也被建议作为胁迫下细胞重编程的功能标记。在本研究中，我们使用黄化大豆（Glycine max（L.）Merr. cv Cresir）幼苗来研究 SA 处理对下胚轴线粒体脂质组成和呼吸特性的影响。作为报告蛋白，详细研究了 AOX 表达，以评估线粒体能量代谢是否发生变化。在从 SA 处理的幼苗中提取的线粒体中，AOX 能力和蛋白含量增加。AOX1 和 AOX2b 转录本均响应 SA 而积累，但动力学不同。观察到外部 NADH 氧化能力降低，而琥珀酸呼吸保持不变。对照和 SA 处理植物中线粒体的磷脂组成相似，但在磷脂酰胆碱、磷脂酰乙醇胺和心磷脂中观察到亚油酸相对含量减少。讨论了观察到的脂肪酸修饰的可能原因及其对线粒体代谢的影响。
