Napieraj Natalia, Janicka Małgorzata, Augustyniak Beata, Reda Małgorzata
Department of Plant Molecular Physiology, Faculty of Biological Science, University of Wrocław, Kanonia 6/8, 50-328 Wrocław, Poland.
Department of Genetic Biochemistry, Faculty of Biotechnology, University of Wrocław, Przybyszewskiego 63/77, 51-148 Wrocław, Poland.
Metabolites. 2023 Sep 21;13(9):1030. doi: 10.3390/metabo13091030.
Polyamines (PAs) are small aliphatic compounds that participate in the plant response to abiotic stresses. They also participate in nitric oxide (NO) production in plants; however, their role in this process remains unknown. Therefore, the study aimed to investigate the role of putrescine (Put) in NO production in the roots of cucumber seedlings subjected to salt stress (120 mM NaCl) for 1 and 24 h. In salinity, exogenous Put can regulate NO levels by managing NO biosynthesis pathways in a time-dependent manner. In cucumber roots exposed to 1 h of salinity, exogenous Put reduced NO level by decreasing nitrate reductase (NR)-dependent NO production and reduced nitric oxide synthase-like (NOS-like) activity. In contrast, during a 24 h salinity exposure, Put treatment boosted NO levels, counteracting the inhibitory effect of salinity on the NR and plasma membrane nitrate reductase (PM-NR) activity in cucumber roots. The role of endogenous Put in salt-induced NO generation was confirmed using Put biosynthesis inhibitors. Furthermore, the application of Put can modulate the NR activity at the genetic and post-translational levels. After 1 h of salt stress, exogenous Put upregulated and expression and downregulated expression. Put also decreased the NR activation state, indicating a reduction in the level of active dephosphorylated NR (dpNR) in the total enzyme pool. Conversely, in the roots of plants subjected to 24 h of salinity, exogenous Put enhanced the NR activation state, indicating an enhancement of the dpNR form in the total NR pool. These changes were accompanied by a modification of endogenous PA content. Application of exogenous Put led to an increase in the amount of Put in the roots and reduced endogenous spermine (Spm) content in cucumber roots under 24 h salinity. The regulatory role of exogenous Put on NO biosynthesis pathways may link with plant mechanisms of response to salt stress.
多胺（PAs）是参与植物对非生物胁迫响应的小分子脂肪族化合物。它们也参与植物中一氧化氮（NO）的产生；然而，它们在这个过程中的作用仍然未知。因此，本研究旨在探究腐胺（Put）在盐胁迫（120 mM NaCl）处理1小时和24小时的黄瓜幼苗根系NO产生中的作用。在盐胁迫条件下，外源Put可以通过以时间依赖的方式调控NO生物合成途径来调节NO水平。在暴露于1小时盐胁迫的黄瓜根系中，外源Put通过降低依赖硝酸还原酶（NR）的NO产生以及降低一氧化氮合酶样（NOS样）活性来降低NO水平。相反，在暴露于24小时盐胁迫期间，Put处理提高了NO水平，抵消了盐胁迫对黄瓜根系中NR和质膜硝酸还原酶（PM-NR）活性的抑制作用。使用Put生物合成抑制剂证实了内源性Put在盐诱导的NO生成中的作用。此外，Put的应用可以在基因和翻译后水平调节NR活性。盐胁迫1小时后，外源Put上调 和 表达并下调 表达。Put还降低了NR的激活状态，表明总酶库中活性去磷酸化NR（dpNR）水平降低。相反，在经受24小时盐胁迫的植物根系中，外源Put增强了NR激活状态，表明总NR库中dpNR形式增加。这些变化伴随着内源性PA含量的改变。外源Put的应用导致根系中Put含量增加，并降低了24小时盐胁迫下黄瓜根系内源性精胺（Spm）含量。外源Put对NO生物合成途径的调节作用可能与植物对盐胁迫的响应机制有关。
