Hasselt University, Environmental Biology, Centre for Environmental Sciences, Agoralaan Building D, B-3590 Diepenbeek, Belgium.
Plant Physiol Biochem. 2013 Feb;63:272-80. doi: 10.1016/j.plaphy.2012.12.005. Epub 2012 Dec 26.
Lipoxygenases (LOXes, EC 1.13.11.12) are involved in growth, development and responses to stress. Earlier results suggested a role in stress generation, signalling and/or responses when Arabidopsis thaliana is exposed to cadmium (Cd), and expression of the cytosolic LOX1 was highly upregulated in the roots after Cd exposure. To investigate the involvement of LOX1 in early metal stress responses, three-week-old wild-type and lox1-1 mutant A. thaliana plants were acutely (24 h) exposed to realistic Cd concentrations (5 and 10 μM) and several oxidative stress and signalling related parameters were studied at transcriptional and biochemical levels. Transcription of several genes encoding ROS producing and scavenging enzymes failed to be induced up to wild-type levels after Cd exposure. Expression of 9-LOX enzymes was inhibited in lox1-1 mutant roots due to lack of functional LOX1 and downregulated LOX5 expression, and the lox1-1 mutation also interfered with the expression of genes involved in jasmonate biosynthesis. LOX1 and RBOHD may be involved in stress signalling from roots to shoots, as the induction of APX2 expression, which is dependent on RBOHD activity, was disrupted in lox1-1 while RBOHD failed to be upregulated. A different pattern of H(2)O(2) production and ascorbate and glutathione levels in lox1-1 mutants after Cd exposure may have indirectly influenced gene expression patterns. Although indirect effects of the lox1-1 mutation on gene expression complicate the determination of exact sensing - signalling - response pathways, the results presented here outline a more refined LOX1 functioning in Cd-induced stress responses that could be used in studies determining the exact involvement of LOX1 in these pathways.
脂氧合酶（LOXes，EC 1.13.11.12）参与生长、发育和应激反应。早期的研究结果表明，在拟南芥暴露于镉（Cd）时，LOXes 参与了胁迫的产生、信号转导和/或响应，并且细胞质 LOX1 的表达在 Cd 暴露后在根部高度上调。为了研究 LOX1 在早期金属胁迫响应中的作用，用现实的 Cd 浓度（5 和 10 μM）对三星期大的野生型和 lox1-1 突变体拟南芥进行急性（24 小时）暴露，并在转录和生化水平上研究了几个与氧化应激和信号转导相关的参数。暴露于 Cd 后，几种产生和清除 ROS 的酶的基因转录未能被诱导至野生型水平。由于缺乏功能性 LOX1，lox1-1 突变体根中的 9-LOX 酶表达被抑制，LOX5 表达下调，并且 lox1-1 突变也干扰了参与茉莉酸生物合成的基因的表达。LOX1 和 RBOHD 可能参与了从根部到茎部的胁迫信号转导，因为依赖于 RBOHD 活性的 APX2 表达的诱导在 lox1-1 中被破坏，而 RBOHD 未能被上调。在 lox1-1 突变体中，Cd 暴露后 H2O2 产生和抗坏血酸和谷胱甘肽水平的不同模式可能间接地影响了基因表达模式。尽管 lox1-1 突变对基因表达的间接影响使确切的感应-信号转导-响应途径的确定变得复杂，但这里提出的结果概述了 LOX1 在 Cd 诱导的胁迫响应中更精细的作用，可用于研究确定 LOX1 在这些途径中的确切作用。
