Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Munich/Neuherberg, Germany.
Plant Physiol. 2009 Nov;151(3):1459-75. doi: 10.1104/pp.109.141994. Epub 2009 Sep 2.
Arabidopsis (Arabidopsis thaliana) NADPH oxidases have been reported to suppress the spread of pathogen- and salicylic acid-induced cell death. Here, we present dual roles of RBOHD (for respiratory burst oxidase homolog D) in an Arabidopsis-Alternaria pathosystem, suggesting either initiation or prevention of cell death dependent on the distance from pathogen attack. Our data demonstrate that a rbohD knockout mutant exhibits increased spread of cell death at the macroscopic level upon inoculation with the fungus Alternaria brassicicola. However, the cellular patterns of reactive oxygen species accumulation and cell death are fundamentally different in the AtrbohD mutant compared with the wild type. Functional RBOHD causes marked extracellular hydrogen peroxide accumulation as well as cell death in distinct, single cells of A. brassicicola-infected wild-type plants. This single cell response is missing in the AtrbohD mutant, where infection triggers spreading-type necrosis preceded by less distinct chloroplastic hydrogen peroxide accumulation in large clusters of cells. While the salicylic acid analog benzothiadiazole induces the action of RBOHD and the development of cell death in infected tissues, the ethylene inhibitor aminoethoxyvinylglycine inhibits cell death, indicating that both salicylic acid and ethylene positively regulate RBOHD and cell death. Moreover, A. brassicicola-infected AtrbohD plants hyperaccumulate ethylene and free salicylic acid compared with the wild type, suggesting negative feedback regulation of salicylic acid and ethylene by RBOHD. We propose that functional RBOHD triggers death in cells that are damaged by fungal infection but simultaneously inhibits death in neighboring cells through the suppression of free salicylic acid and ethylene levels.
拟南芥（Arabidopsis thaliana）NADPH 氧化酶已被报道可抑制病原体和水杨酸诱导的细胞死亡的扩散。在这里，我们提出了 RBOHD（呼吸爆发氧化酶同源物 D）在拟南芥-链格孢菌病理系统中的双重作用，表明细胞死亡的发生或预防取决于与病原体攻击的距离。我们的数据表明，在接种真菌Alternaria brassicicola 时，rbohD 敲除突变体在宏观水平上表现出细胞死亡的扩散增加。然而，与野生型相比，AtRbohD 突变体中活性氧物质积累和细胞死亡的细胞模式有根本的不同。功能性 RBOHD 导致明显的细胞外过氧化氢积累以及野生型植物中受感染的Alternaria brassicicola 单个细胞中的细胞死亡。这种单细胞反应在 AtRbohD 突变体中缺失，在 AtRbohD 突变体中，感染引发扩散型坏死，随后在大簇细胞中观察到不太明显的质体过氧化氢积累。虽然水杨酸类似物苯并噻二唑诱导 RBOHD 的作用和受感染组织中细胞死亡的发展，但是乙烯抑制剂氨基乙氧乙烯基甘氨酸抑制细胞死亡，表明水杨酸和乙烯都正向调节 RBOHD 和细胞死亡。此外，与野生型相比，受 Alternaria brassicicola 感染的 AtRbohD 植物中乙烯和游离水杨酸的含量更高，这表明 RBOHD 通过负反馈调节水杨酸和乙烯。我们提出功能性 RBOHD 通过抑制游离水杨酸和乙烯水平，在被真菌感染的细胞中引发死亡，但同时抑制邻近细胞中的死亡。
