Poór Péter, Patyi Gábor, Takács Zoltán, Szekeres András, Bódi Nikolett, Bagyánszki Mária, Tari Irma
Department of Plant Biology, University of Szeged, Közép fasor 52, Szeged, 6726, Hungary.
Department of Microbiology, University of Szeged, Közép fasor 52, Szeged, 6726, Hungary.
J Plant Res. 2019 Mar;132(2):273-283. doi: 10.1007/s10265-019-01085-y. Epub 2019 Feb 13.
The growth regulator, salicylic acid (SA) plays an important role in the induction of cell death in plants. Production of reactive oxygen species (ROS) by mitochondrial electron transport chain (mtETC), cytochrome c (cyt c) release from mitochondria and loss of mitochondrial integrity can be observed during cell death execution in plant tissues. The aim of this work was to study the putative role of hexokinases (HXKs) in the initiation of cell death using tomato (Solanum lycopersicum L.) leaves and mitochondria isolated from plants exposed to a sublethal, 0.1 mM and a cell death-inducing, 1 mM concentrations of SA. Both treatments enhanced ROS and nitric oxide (NO) production in the leaves, which contributed to a concentration-dependent loss of membrane integrity. Images prepared by transmission electron microscopy showed swelling and disorganisation of mitochondrial cristae and vacuolization of mitochondria after SA exposure. Using post-embedding immunohistochemistry, cyt c release from mitochondria was also detected after 1 mM SA treatment. Both SA treatments decreased the activity and transcript levels of HXKs in the leaves and the total mtHXK activity in the mitochondrial fraction. The role of mitochondrial hexokinases (mtHXKs) in ROS and NO production of isolated mitochondria was investigated by the addition of HXK substrate, glucose (Glc) and a specific HXK inhibitor, N-acetylglucosamine (NAG) to the mitochondrial suspension. Both SA treatments enhanced ROS production by mtETC in the presence of succinate and ADP, which was slightly inhibited by Glc and increased significantly by NAG in control and in 0.1 mM SA-treated mitochondria. These changes were not significant at 1 mM SA, which caused disorganisation of mitochondrial membranes. Thus the inhibition of mtHXK activity can contribute to the mitochondrial ROS production, but it is not involved in NO generation in SA-treated leaf mitochondria suggesting that SA can promote cell death by suppressing mtHXK transcription and activity.
生长调节剂水杨酸（SA）在植物细胞死亡诱导过程中发挥着重要作用。在植物组织细胞死亡过程中，可以观察到线粒体电子传递链（mtETC）产生活性氧（ROS）、细胞色素c（cyt c）从线粒体释放以及线粒体完整性丧失。本研究旨在利用番茄（Solanum lycopersicum L.）叶片和从暴露于亚致死浓度（0.1 mM）和诱导细胞死亡浓度（1 mM）SA的植物中分离得到的线粒体，研究己糖激酶（HXKs）在细胞死亡起始过程中的假定作用。两种处理均增强了叶片中ROS和一氧化氮（NO）的产生，这导致了浓度依赖性的膜完整性丧失。透射电子显微镜制备的图像显示，SA处理后线粒体嵴肿胀、紊乱，线粒体空泡化。采用包埋后免疫组织化学方法，还检测到1 mM SA处理后cyt c从线粒体释放。两种SA处理均降低了叶片中HXKs的活性和转录水平以及线粒体部分的总mtHXK活性。通过向线粒体悬浮液中添加HXK底物葡萄糖（Glc）和特异性HXK抑制剂N-乙酰葡糖胺（NAG），研究了线粒体己糖激酶（mtHXKs）在分离线粒体ROS和NO产生中的作用。在琥珀酸和ADP存在的情况下，两种SA处理均增强了mtETC产生的ROS，在对照和0.1 mM SA处理的线粒体中，Glc对其有轻微抑制作用，NAG则使其显著增加。在1 mM SA时，这些变化不显著，因为1 mM SA导致线粒体膜紊乱。因此，mtHXK活性的抑制可能有助于线粒体ROS的产生，但它不参与SA处理的叶片线粒体中NO的生成，这表明SA可以通过抑制mtHXK转录和活性来促进细胞死亡。
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