Guan L M, Scandalios J G
Department of Genetics, North Carolina State University, Raleigh, NC 27695-7614, USA.
Free Radic Biol Med. 2000 Apr 15;28(8):1182-90. doi: 10.1016/s0891-5849(00)00212-4.
The effect of wounding on catalase expression was examined in embryos and leaves of maize. All three Cat genes are upregulated in response to wounding in immature embryos. Cat expression also increased in response to jasmonic acid (JA), raising the possibility that JA and wounding may share a common signal transduction pathway in upregulating Cat mRNA in immature embryos. In young leaves, only Cat1 and Cat3 transcripts increase in response to wounding, but JA does not play a role. Cat1 and Cat3 transcript accumulation also increases in response to wounding in both wild-type and mutant leaves deficient in abscisic acid (ABA), implying that Cat1 and Cat3 induction in response to wounding is not mediated by ABA in leaves. Transient assays using the Cat1 promoter fused with the reporter gene Gus, showed that the DNA sequence motif responsible for Cat1 upregulation by wounding overlaps with the ABA-responsive element (ABRE, G-box) in the Cat1 promoter. The exact nature of the signals triggering the Cat responses to wounding is not clear at this point, but some evidence indicates that reactive oxygen species (ROS) play a role in this response. In fact, we have found that endogenous H(2)O(2) levels increase in wounded leaves. Thus, wounding may indirectly induce the production of H(2)O(2) in leaves, triggering the antioxidant response.
在玉米的胚胎和叶片中研究了创伤对过氧化氢酶表达的影响。在未成熟胚胎中，所有三个过氧化氢酶基因（Cat）均因创伤而上调。过氧化氢酶的表达也因茉莉酸（JA）而增加，这增加了一种可能性，即茉莉酸和创伤可能在未成熟胚胎中上调过氧化氢酶信使核糖核酸（Cat mRNA）时共享一条共同的信号转导途径。在幼叶中，只有Cat1和Cat3转录本因创伤而增加，但茉莉酸不起作用。在缺乏脱落酸（ABA）的野生型和突变型叶片中，Cat1和Cat3转录本积累也因创伤而增加，这意味着叶片中创伤诱导的Cat1和Cat3不是由脱落酸介导的。使用与报告基因Gus融合的Cat1启动子进行的瞬时分析表明，负责创伤上调Cat1的DNA序列基序与Cat1启动子中的脱落酸反应元件（ABRE，G盒）重叠。目前尚不清楚触发过氧化氢酶对创伤反应的信号的确切性质，但一些证据表明活性氧（ROS）在这种反应中起作用。事实上，我们发现受伤叶片中的内源性过氧化氢（H₂O₂）水平会升高。因此，创伤可能间接诱导叶片中过氧化氢的产生，触发抗氧化反应。
