Modulation of the hormone setting by Rhodococcus fascians results in ectopic KNOX activation in Arabidopsis
Modulation of the hormone setting by Rhodococcus fascians results in ectopic KNOX activation in Arabidopsis
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DOI：
10.1104/pp.107.113969
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发表时间：
2008-03-01
期刊：
影响因子：
7.4
通讯作者：
Vereecke, Danny
中科院分区：
文献类型：
--
作者：
Depuydt, Stephen;Dolezal, Karel;Vereecke, Danny
生物营养放线菌筋膜红球菌对植物发育具有深远的影响，其症状的一个常见方面是受感染的叶子变形。在拟南芥中，感染后形成的锯齿状叶缘类似于异位表达 KNOTTED 样同源框 (KNOX) 基因的转基因植物的叶子表型。通过转录谱分析，我们证明 I 类 KNOX 基因在有症状的叶子中转录。功能分析表明，BREVIPEDICELLUS/KNOTTED-LIKE1 和主要的 SHOOT MERISTEMLESS 对于观察到的叶片解剖至关重要。然而，这些结果也将 KNOX 基因定位在由 R. fascians 感染触发的信号级联下游。拟南芥响应调节器 5 的激活速度要快得多，以及控制细胞分裂素 (CK) 水平的稳态和反馈机制的建立，支持由于病原体的分泌而在受感染植物中过度表达这种激素，从而将 CK 响应置于级联中的较高位置。激素测量显示测试的 CK 净减少，表明细菌的分泌和植物的降解处于平衡，或者如 35S:CKX 植物的强烈反应所示，表明其他 CK 正在发挥作用。在相互作用的早期时间点，赤霉素 2-氧化酶的激活可能会产生有利于分生组织活动的局部激素环境，从而引起叶片锯齿。研究结果在症状发展、植物防御的逃避以及R. fascians建立特定生态位的背景下进行了讨论。
The biotrophic actinomycete Rhodococcus fascians has a profound impact on plant development and a common aspect of the symptomatology is the deformation of infected leaves. In Arabidopsis ( Arabidopsis thaliana), the serrated leaf margins formed upon infection resemble the leaf phenotype of transgenic plants with ectopic expression of KNOTTED-like homeobox (KNOX) genes. Through transcript profiling, we demonstrate that class-I KNOX genes are transcribed in symptomatic leaves. Functional analysis revealed that BREVIPEDICELLUS/KNOTTED-LIKE1 and mainly SHOOT MERISTEMLESS were essential for the observed leaf dissection. However, these results also positioned the KNOX genes downstream in the signaling cascade triggered by R. fascians infection. The much faster activation of ARABIDOPSIS RESPONSE REGULATOR5 and the establishment of homeostatic and feedback mechanisms to control cytokinin (CK) levels support the overrepresentation of this hormone in infected plants due to the secretion by the pathogen, thereby placing the CK response high up in the cascade. Hormone measurements show a net decrease of tested CKs, indicating either that secretion by the bacterium and degradation by the plant are in balance, or, as suggested by the strong reaction of 35S:CKX plants, that other CKs are at play. At early time points of the interaction, activation of gibberellin 2-oxidase presumably installs a local hormonal setting favorable for meristematic activity that provokes leaf serrations. The results are discussed in the context of symptom development, evasion of plant defense, and the establishment of a specific niche by R. fascians.