Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei, Taiwan.
Plant Biol (Stuttg). 2013 Sep;15(5):832-40. doi: 10.1111/j.1438-8677.2012.00685.x. Epub 2012 Nov 5.
The gene, indole-3-butyric acid (IBA)-RESPONSE (IBR) 3, is thought to participate in peroxisomal β-oxidation of IBA to indole-3-acetic acid. Here we show that IBR3 may also play a role in Arabidopsis thaliana defence response to microbial pathogens. IBR3 is up-regulated during infection by virulent Pseudomonas syringae pv. tomato (Pst) DC3000 bacteria. Although mutant ibr3-4 did not show a pathogen phenotype, lines overexpressing IBR3 demonstrated enhanced susceptibility to Pst DC3000. Increased susceptibility phenotypes of IBR3 overexpressors were correlated with defective SA defence signalling and impairment of pattern-triggered immunity (PTI) activation. Notably, reactive oxygen species production was reduced in IBR3 overexpressors after treatment with the microbe-associated molecular patterns flg22 and efl26. Later PTI responses, such as accumulation of FRK1 transcripts and callose deposition were also reduced in transgenics overexpressing IBR3 after inoculation with the Type III secretion system deficient bacterial mutant Pst DC3000 hrcC or treatment with flg22 or elf26. Importantly, overexpression of IBR3 did not affect indole-3-acetic acid content or auxin-responsive gene expression. These results suggest a novel role for IBR3 in A. thaliana defence response against bacterial pathogens.
基因吲哚-3-丁酸（IBA）-响应（IBR）3 被认为参与 IBA 向吲哚-3-乙酸的过氧化物体β-氧化。在这里，我们表明 IBR3 也可能在拟南芥对微生物病原体的防御反应中发挥作用。在感染强毒力的丁香假单胞菌 pv.番茄（Pst）DC3000 细菌时，IBR3 上调。尽管 ibr3-4 突变体没有表现出病原体表型，但过表达 IBR3 的系表现出对 Pst DC3000 的敏感性增加。IBR3 过表达系的敏感性增加表型与 SA 防御信号缺陷和模式触发免疫（PTI）激活受损相关。值得注意的是，在用微生物相关分子模式 flg22 和 efl26 处理后，IBR3 过表达系中的活性氧产生减少。在过表达 IBR3 的转基因植物中，PTI 反应的后期，如 FRK1 转录物的积累和胼胝质的沉积，在接种 III 型分泌系统缺陷的细菌突变体 Pst DC3000 hrcC 或用 flg22 或 elf26 处理后也减少。重要的是，过表达 IBR3 不影响吲哚-3-乙酸含量或生长素响应基因的表达。这些结果表明 IBR3 在拟南芥对细菌病原体的防御反应中具有新的作用。
