Ascorbic acid accumulates as a defense response to Turnip mosaic virus in resistant Brassica rapa cultivars.
Ascorbic acid accumulates as a defense response to Turnip mosaic virus in resistant Brassica rapa cultivars.
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DOI：
10.1093/jxb/erw223
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发表时间：
2016-07
影响因子：
6.9
通讯作者：
Inukai T
中科院分区：
文献类型：
--
作者：
Fujiwara A;Togawa S;Hikawa T;Matsuura H;Masuta C;Inukai T
抗坏血酸积累是油菜对TuMV的潜在抗性反应，通过氧化和循环途径的改变介导。我们最初观察到，含有芜菁花叶病毒（TuMV）抗性基因Rnt1-1的油菜品种在感染TuMV后积累了高水平的内源性抗坏血酸（AS）和脱氢抗坏血酸（DHA）。我们假设AS+DHA （TAA）水平的升高可能对rnt1 -1介导的抗性有贡献，并在B. rapa和拟南芥植物上进行了一系列实验。在易感品种上添加l-半乳糖（AS合成的关键底物）可使TAA水平提高约2倍，并在一定程度上增强病毒抗性。为了证实TAA水平与病毒抗性之间存在正相关，我们分析了AS通路中的两个拟南芥敲除突变体（ao和vtc1）；ao和vtc1植株的TAA含量分别显著升高和降低。虽然ao植株对TuMV的抗性增强，但vtc1植株比对照更敏感，这支持了我们的假设。当我们分析TuMV感染后AS通路相关基因的表达谱时，我们发现观察到的TAA增加主要是由于AS氧化减少和AS循环激活引起的。研究结果表明，茉莉酸（jasmonic acid， JA）可能在TAA积累过程中起重要作用。综上所述，研究人员推断，油菜植株中TAA积累的增加至少部分是由ja依赖的信号通路介导的，并且可能对病毒抗性有重要作用。
Ascorbic acid accumulation is a potential resistance response to TuMV in Brassica rapa that is mediated via alterations in oxidation and recycling pathways. We initially observed that Brassica rapa cultivars containing the Turnip mosaic virus (TuMV) resistance gene, Rnt1-1, accumulated a high level of endogenous ascorbic acid (AS) and dehydroascobic acid (DHA) when infected with TuMV. We here hypothesized a possible contribution of an elevated level of AS+DHA (TAA) to the Rnt1-1-mediated resistance, and conducted a series of experiments using B. rapa and Arabidopsis plants. The application of l-galactose (the key substrate in AS synthesis) to a susceptible cultivar could increase the TAA level ~2-fold, and simultaneously lead to some degree of enhanced viral resistance. To confirm some positive correlation between TAA levels and viral resistance, we analyzed two Arabidopsis knockout mutants (ao and vtc1) in the AS pathways; the TAA levels were significantly increased and decreased in ao and vtc1 plants, respectively. While the ao plants showed enhanced resistance to TuMV, vtc1 plants were more susceptible than the control, supporting our hypothesis. When we analyzed the expression profiles of the genes involved in the AS pathways upon TuMV infection, we found that the observed TAA increase was mainly brought about by the reduction of AS oxidation and activation of AS recycling. We then investigated the secondary signals that regulate endogenous TAA levels in response to viral infection, and found that jasmonic acid (JA) might play an important role in TAA accumulation. In conclusion, we reason that the elevated TAA accumulation in B. rapa plants would be at least partly mediated by the JA-dependent signaling pathway and may significantly contribute to viral resistance.