Menga Valeria, Trono Daniela
Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria, Centro di Ricerca Cerealicoltura e Colture Industriali, S.S. 673, Km 25,200, 71122 Foggia, Italy.
Plants (Basel). 2020 Sep 18;9(9):1233. doi: 10.3390/plants9091233.
In plants, lipoxygenases (LOXs) are involved in various processes, such as growth, development, and response to stress cues. In the present study, the expression pattern of six durum wheat LOX-encoding genes (, , , , and ) under hyperosmotic stress was investigated. With osmotic (0.42 M mannitol) and salt (0.21 M NaCl) stress imposed at the early stages of seedling growth, a strong induction of the gene expression in the shoots paralleled an equally strong increase in the LOX activity. Enhanced levels of malondialdehyde (MDA) and increased rates of superoxide anion generation were also observed as a result of the stress imposition. Sequence analysis of the TdLOX2 encoded by the gene revealed that it belonged to the type-1 9-LOX group. When overexpressed in , TdLOX2 exhibited normal enzyme activity, high sensitivity to specific LOX inhibitors, with 76% and 99% inhibition by salicylhydroxamic and propyl gallate, respectively, and a preference for linoleic acid as substrate, which was converted exclusively to its corresponding 13-hydroperoxide. This unexpected positional specificity could be related to the unusual TV/K motif that in TdLOX2 replaces the canonical TV/R motif of 9-LOXs. Treatment of seedlings with propyl gallate strongly suppressed the increase in LOX activity induced by the hyperosmotic stress; the MDA accumulation was also reduced but less markedly, whereas the rate of superoxide anion generation was even more increased. Overall, our findings suggest that the up-regulation of the gene is a component of the durum wheat response to hyperosmotic stress and that TdLOX2 may act by counteracting the excessive generation of harmful reactive oxygen species responsible for the oxidative damages that occur in plants under stress.
在植物中，脂氧合酶（LOXs）参与多种过程，如生长、发育以及对胁迫信号的响应。在本研究中，对六个硬粒小麦LOX编码基因（、、、、和）在高渗胁迫下的表达模式进行了研究。在幼苗生长早期施加渗透胁迫（0.42 M甘露醇）和盐胁迫（0.21 M NaCl）时，茎中基因表达的强烈诱导与LOX活性的同等强烈增加平行。由于胁迫的施加，还观察到丙二醛（MDA）水平升高和超氧阴离子生成速率增加。对基因编码的TdLOX2进行序列分析表明，它属于1型9-LOX组。当在中过表达时，TdLOX2表现出正常的酶活性，对特定的LOX抑制剂高度敏感，水杨羟肟酸和没食子酸丙酯分别抑制76%和99%，并且优先选择亚油酸作为底物，亚油酸仅被转化为其相应的13-氢过氧化物。这种意外的位置特异性可能与不寻常的TV/K基序有关，在TdLOX2中该基序取代了9-LOXs的典型TV/R基序。用没食子酸丙酯处理幼苗强烈抑制了高渗胁迫诱导的LOX活性增加；MDA积累也有所减少，但不太明显，而超氧阴离子生成速率甚至进一步增加。总体而言，我们的研究结果表明，基因的上调是硬粒小麦对高渗胁迫响应的一个组成部分，并且TdLOX2可能通过抵消负责植物在胁迫下发生氧化损伤的有害活性氧的过度产生而起作用。
