Rapala-Kozik Maria, Kowalska Ewa, Ostrowska Katarzyna
Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
J Exp Bot. 2008;59(15):4133-43. doi: 10.1093/jxb/ern253. Epub 2008 Oct 21.
The responses of plants to abiotic stress involve the up-regulation of numerous metabolic pathways, including several major routes that engage thiamine diphosphate (TDP)-dependent enzymes. This suggests that the metabolism of thiamine (vitamin B1) and its phosphate esters in plants may be modulated under various stress conditions. In the present study, Zea mays seedlings were used as a model system to analyse for any relation between the plant response to abiotic stress and the properties of thiamine biosynthesis and activation. Conditions of drought, high salt, and oxidative stress were induced by polyethylene glycol, sodium chloride, and hydrogen peroxide, respectively. The expected increases in the abscisic acid levels and in the activities of antioxidant enzymes including catalase, ascorbate peroxidase, and glutathione reductase were found under each stress condition. The total thiamine compound content in the maize seedling leaves increased under each stress condition applied, with the strongest effects on these levels observed under the oxidative stress treatment. This increase was also found to be associated with changes in the relative distribution of free thiamine, thiamine monophosphate (TMP), and TDP. Surprisingly, the activity of the thiamine synthesizing enzyme, TMP synthase, responded poorly to abiotic stress, in contrast to the significant enhancement found for the activities of the TDP synthesizing enzyme, thiamine pyrophosphokinase, and a number of the TDP/TMP phosphatases. Finally, a moderate increase in the activity of transketolase, one of the major TDP-dependent enzymes, was detectable under conditions of salt and oxidative stress. These findings suggest a role of thiamine metabolism in the plant response to environmental stress.
植物对非生物胁迫的响应涉及众多代谢途径的上调，包括几条涉及硫胺二磷酸（TDP）依赖性酶的主要途径。这表明植物中硫胺素（维生素B1）及其磷酸酯的代谢可能在各种胁迫条件下受到调节。在本研究中，以玉米幼苗作为模型系统，分析植物对非生物胁迫的响应与硫胺素生物合成及激活特性之间的关系。分别用聚乙二醇、氯化钠和过氧化氢诱导干旱、高盐和氧化胁迫条件。在每种胁迫条件下，均发现脱落酸水平以及包括过氧化氢酶、抗坏血酸过氧化物酶和谷胱甘肽还原酶在内的抗氧化酶活性出现预期的增加。在所施加的每种胁迫条件下，玉米幼苗叶片中的硫胺素化合物总含量均增加，在氧化胁迫处理下观察到对这些水平的影响最为强烈。还发现这种增加与游离硫胺素、硫胺素单磷酸（TMP）和TDP的相对分布变化有关。令人惊讶的是，与TDP合成酶硫胺素焦磷酸激酶以及多种TDP/TMP磷酸酶活性的显著增强形成对比的是，硫胺素合成酶TMP合酶的活性对非生物胁迫反应不佳。最后，在盐胁迫和氧化胁迫条件下，可检测到主要的TDP依赖性酶之一转酮醇酶的活性适度增加。这些发现表明硫胺素代谢在植物对环境胁迫的响应中发挥作用。
