The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA.
Mol Plant. 2013 May;6(3):802-16. doi: 10.1093/mp/sss091. Epub 2012 Sep 17.
Arabidopsis non-expressor of PR1 (NPR1) is a transcription co-activator that plays a central role in regulating the transcriptional response to plant pathogens. The NPR family consists of NPR1 and five NPR1-like genes. The NPR1 paralog NPR3 has recently been shown to function as a receptor of the plant hormone salicylic acid and to mediate proteosomal degradation of NPR1. The function of NPR3 protein during early flower development was revealed through a detailed molecular-genetic analysis including promoter transcriptional fusion analysis, phenotype characterization of npr3-3 mutants/overexpressors, and whole-plant fitness analysis. The physical interaction between NPR3 and NPR1/TGA2 was explored using bimolecular fluorescence complementation analysis in onion epidermal cells. Here, we show that NPR3 expression was strongest in the petals and sepals of developing flowers and declined after flower opening. Consistently with this observation, an npr3 knockout mutant displayed enhanced resistance to Pseudomonas syringae infection of immature flowers, but not leaves. Developing npr3 flowers exhibited increased levels of basal and induced PR1 transcript accumulation. However, the npr3 mutant showed lower fitness compared to Col-0 in the absence of pathogen. Moreover, NPR3 was shown to interact with NPR1 and TGA2 in vivo. Our data suggest that NPR3 is a negative regulator of defense responses during early flower development and it may function through the association with both NPR1 and TGA2.
拟南芥非表达 PR1（NPR1）是一种转录共激活因子，在调节植物病原体的转录反应中发挥核心作用。NPR 家族由 NPR1 和五个 NPR1 样基因组成。最近的研究表明，NPR1 旁系 NPR3 作为植物激素水杨酸的受体发挥作用，并介导 NPR1 的蛋白体降解。通过包括启动子转录融合分析、npr3-3 突变体/过表达体的表型特征分析和全植物适应性分析在内的详细分子遗传分析，揭示了 NPR3 蛋白在早期花发育过程中的功能。使用双分子荧光互补分析在洋葱表皮细胞中探索了 NPR3 和 NPR1/TGA2 之间的物理相互作用。在这里，我们表明 NPR3 的表达在发育中的花朵的花瓣和萼片中最强，并在花朵开放后下降。与这一观察结果一致，npr3 敲除突变体对未成熟花朵的丁香假单胞菌感染表现出增强的抗性，但对叶片没有。发育中的 npr3 花朵表现出基础和诱导 PR1 转录物积累的增加水平。然而，与 Col-0 相比，在没有病原体的情况下，npr3 突变体的适应性较低。此外，NPR3 被证明在体内与 NPR1 和 TGA2 相互作用。我们的数据表明，NPR3 是早期花发育过程中防御反应的负调节剂，它可能通过与 NPR1 和 TGA2 的关联起作用。
