Laboratory of Molecular Plant Pathology, School of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-713, Republic of Korea.
Mol Plant Microbe Interact. 2011 Jan;24(1):68-78. doi: 10.1094/MPMI-02-10-0030.
Pathogen-induced programmed cell death (PCD) is intimately linked with disease resistance and susceptibility. However, the molecular components regulating PCD, including hypersensitive and susceptible cell death, are largely unknown in plants. In this study, we show that pathogen-induced Capsicum annuum hypersensitive induced reaction 1 (CaHIR1) and leucine-rich repeat 1 (CaLRR1) function as distinct plant PCD regulators in pepper plants during Xanthomonas campestris pv. vesicatoria infection. Confocal microscopy and protein gel blot analyses revealed that CaLRR1 and CaHIR1 localize to the extracellular matrix and plasma membrane (PM), respectively. Bimolecular fluorescent complementation and coimmunoprecipitation assays showed that the extracellular CaLRR1 specifically binds to the PM-located CaHIR1 in pepper leaves. Overexpression of CaHIR1 triggered pathogen-independent cell death in pepper and Nicotiana benthamiana plants but not in yeast cells. Virus-induced gene silencing (VIGS) of CaLRR1 and CaHIR1 distinctly strengthened and compromised hypersensitive and susceptible cell death in pepper plants, respectively. Endogenous salicylic acid levels and pathogenesis-related gene transcripts were elevated in CaHIR1-silenced plants. VIGS of NbLRR1 and NbHIR1, the N. benthamiana orthologs of CaLRR1 and CaHIR1, regulated Bax- and avrPto-/Pto-induced PCD. Taken together, these results suggest that leucine-rich repeat and hypersensitive induced reaction proteins may act as cell-death regulators associated with plant immunity and disease.
病原体诱导的程序性细胞死亡（PCD）与疾病抗性和易感性密切相关。然而，在植物中，调节 PCD 的分子成分（包括过敏性和敏感性细胞死亡）在很大程度上尚不清楚。在这项研究中，我们表明，在辣椒疫霉菌感染期间，病原体诱导的辣椒过敏诱导反应 1（CaHIR1）和富含亮氨酸重复 1（CaLRR1）在辣椒植物中作为不同的植物 PCD 调节剂发挥作用。共聚焦显微镜和蛋白质凝胶印迹分析表明，CaLRR1 和 CaHIR1 分别定位于细胞外基质和质膜（PM）。双分子荧光互补和共免疫沉淀测定表明，细胞外 CaLRR1 特异性结合于辣椒叶片中位于 PM 的 CaHIR1。过表达 CaHIR1 可在辣椒和黄花烟植株中触发与病原体无关的细胞死亡，但在酵母细胞中则不会。CaLRR1 和 CaHIR1 的病毒诱导基因沉默（VIGS）分别显著增强和削弱了辣椒植株中过敏性和敏感性细胞死亡。CaHIR1 沉默植株中内源性水杨酸水平和病程相关基因转录物升高。NbLRR1 和 NbHIR1 的 VIGS，即 CaLRR1 和 CaHIR1 的黄花烟同源物，调节 Bax 和 avrPto-/Pto 诱导的 PCD。总之，这些结果表明富含亮氨酸重复和过敏诱导反应蛋白可能作为与植物免疫和疾病相关的细胞死亡调节剂发挥作用。
