Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization and Hunan Provincial Key Laboratory of Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University, Changsha, Hunan 410128, China.
Plant Physiol. 2012 May;159(1):239-50. doi: 10.1104/pp.111.192617. Epub 2012 Mar 1.
The components in plant signal transduction pathways are intertwined and affect each other to coordinate plant growth, development, and defenses to stresses. The role of ubiquitination in connecting these pathways, particularly plant innate immunity and flowering, is largely unknown. Here, we report the dual roles for the Arabidopsis (Arabidopsis thaliana) Plant U-box protein13 (PUB13) in defense and flowering time control. In vitro ubiquitination assays indicated that PUB13 is an active E3 ubiquitin ligase and that the intact U-box domain is required for the E3 ligase activity. Disruption of the PUB13 gene by T-DNA insertion results in spontaneous cell death, the accumulation of hydrogen peroxide and salicylic acid (SA), and elevated resistance to biotrophic pathogens but increased susceptibility to necrotrophic pathogens. The cell death, hydrogen peroxide accumulation, and resistance to necrotrophic pathogens in pub13 are enhanced when plants are pretreated with high humidity. Importantly, pub13 also shows early flowering under middle- and long-day conditions, in which the expression of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 and FLOWERING LOCUS T is induced while FLOWERING LOCUS C expression is suppressed. Finally, we found that two components involved in the SA-mediated signaling pathway, SID2 and PAD4, are required for the defense and flowering-time phenotypes caused by the loss of function of PUB13. Taken together, our data demonstrate that PUB13 acts as an important node connecting SA-dependent defense signaling and flowering time regulation in Arabidopsis.
植物信号转导途径中的成分相互交织，相互影响，以协调植物的生长、发育和对胁迫的防御。泛素化在连接这些途径中的作用，特别是植物先天免疫和开花，在很大程度上是未知的。在这里，我们报告了拟南芥（Arabidopsis thaliana）植物 U -box 蛋白 13（PUB13）在防御和开花时间控制中的双重作用。体外泛素化测定表明，PUB13 是一种活性 E3 泛素连接酶，完整的 U-box 结构域是 E3 泛素连接酶活性所必需的。通过 T-DNA 插入破坏 PUB13 基因导致自发性细胞死亡、过氧化氢和水杨酸（SA）的积累以及对生物营养性病原体的抗性增强，但对坏死性病原体的敏感性增加。pub13 中的细胞死亡、过氧化氢积累和对坏死性病原体的敏感性在高湿度预处理时增强。重要的是，pub13 在中长日照条件下也表现出早期开花，其中 SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 和 FLOWERING LOCUS T 的表达被诱导，而 FLOWERING LOCUS C 的表达被抑制。最后，我们发现参与 SA 介导的信号通路的两个成分，SID2 和 PAD4，是 PUB13 功能丧失引起的防御和开花时间表型所必需的。总之，我们的数据表明，PUB13 作为一个重要的节点，连接 SA 依赖的防御信号和拟南芥开花时间的调节。
