Yoda Hiroshi, Fujimura Kazuki, Takahashi Hideyuki, Munemura Ikuko, Uchimiya Hirofumi, Sano Hiroshi
Research and Education Center for Genetic Information, Nara Institute of Science and Technology, Nara, 630-0192, Japan.
Plant Mol Biol. 2009 May;70(1-2):103-12. doi: 10.1007/s11103-009-9459-0. Epub 2009 Feb 4.
The hypersensitive response (HR) is a powerful resistance system that plants have developed against pathogen attack. There are two major pathways for HR induction; one is through recognition of the pathogen by a specific host protein, and is known as the host HR. The other is through common biochemical changes upon infection--the nonhost HR. We previously demonstrated that hydrogen peroxide derived from polyamine degradation by polyamine oxidase triggers the typical host HR in tobacco plants upon infection with tobacco mosaic virus. However, it remains to be determined whether or not polyamines are involved in the nonhost HR in tobacco, and in the host HR in other plant species. When tobacco plants were infected with Pseudomonas cichorii, a representative nonhost pathogen, transcripts for six genes encoding enzymes for polyamine metabolism were simultaneously induced, and polyamines were accumulated in apoplasts. Hydrogen peroxide was concomitantly produced and hypersensitive cell death occurred at infected sites. Silencing of polyamine oxidase by the virus-induced gene silencing method resulted in suppression of hydrogen peroxide production and in disappearance of visible hypersensitive cell death with an increase in bacterial growth. Our results indicated that polyamines served as the source of hydrogen peroxide during the nonhost HR in tobacco plants. Further analysis revealed that polyamines were accumulated in apoplasts of Arabidopsis thaliana infected with Pseudomonas syringae, and of rice infected with Magnaporthe grisea, both causing the typical host HR. As in tobacco, it is conceivable that the same mechanism operates for nonhost HR in these plants. Our present observations thus suggested that polyamines are commonly utilized as the source of hydrogen peroxide during host- and nonhost HRs in higher plants.
过敏反应（HR）是植物针对病原体攻击所形成的强大抗性系统。诱导HR有两条主要途径；一条是通过特定宿主蛋白识别病原体，即宿主HR。另一条是通过感染后的常见生化变化——非宿主HR。我们之前证明，烟草花叶病毒感染烟草植株时，多胺氧化酶降解多胺产生的过氧化氢会触发典型的宿主HR。然而，多胺是否参与烟草的非宿主HR以及其他植物物种的宿主HR仍有待确定。当烟草植株被非宿主病原体代表菊苣假单胞菌感染时，编码多胺代谢酶的六个基因的转录本同时被诱导，并且多胺在质外体中积累。同时产生了过氧化氢，感染部位发生了过敏细胞死亡。通过病毒诱导基因沉默方法使多胺氧化酶沉默，导致过氧化氢产生受到抑制，可见的过敏细胞死亡消失，细菌生长增加。我们的结果表明，在烟草植株的非宿主HR过程中，多胺作为过氧化氢的来源。进一步分析发现，在被丁香假单胞菌感染的拟南芥以及被稻瘟病菌感染的水稻的质外体中多胺都有积累，这两种情况都会引发典型的宿主HR。与烟草一样，可以想象这些植物的非宿主HR也有相同的机制在起作用。因此，我们目前的观察结果表明，在高等植物的宿主和非宿主HR过程中，多胺通常被用作过氧化氢的来源。
