Morita-Yamamuro Chizuko, Tsutsui Tomokazu, Sato Masanao, Yoshioka Hirofumi, Tamaoki Masanori, Ogawa Daisuke, Matsuura Hideyuki, Yoshihara Teruhiko, Ikeda Akira, Uyeda Ichiro, Yamaguchi Junji
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Kita-ku N10-W8, Sapporo, 060-0810 Japan.
Plant Cell Physiol. 2005 Jun;46(6):902-12. doi: 10.1093/pcp/pci095. Epub 2005 Mar 30.
To clarify the processes involved in plant immunity, we have isolated and characterized a single recessive Arabidopsis mutant, cad1 (constitutively activated cell death 1), which shows a phenotype that mimics the lesions seen in the hypersensitive response (HR). This mutant shows spontaneously activated expression of pathogenesis-related (PR) genes, and leading to a 32-fold increase in salicylic acid (SA). Inoculation of cad1 mutant plants with Pseudomonas syringae pv tomato DC3000 shows that the cad1 mutation results in the restriction of bacterial growth. Cloning of CAD1 reveals that this gene encodes a protein containing a domain with significant homology to the MACPF (membrane attack complex and perforin) domain of complement components and perforin proteins that are involved in innate immunity in animals. Furthermore, cell death is suppressed in transgenic cad1 plants expressing nahG, which encodes an SA-degrading enzyme. We therefore conclude that the CAD1 protein negatively controls the SA-mediated pathway of programmed cell death in plant immunity.
为了阐明植物免疫所涉及的过程，我们分离并鉴定了一个单一的隐性拟南芥突变体cad1（组成型激活细胞死亡1），该突变体表现出一种类似于过敏反应（HR）中所见损伤的表型。这个突变体显示出病程相关（PR）基因的自发激活表达，并导致水杨酸（SA）增加32倍。用丁香假单胞菌番茄致病变种DC3000接种cad1突变体植物表明，cad1突变导致细菌生长受限。CAD1的克隆揭示，该基因编码一种蛋白质，该蛋白质含有一个与补体成分和穿孔素蛋白的MACPF（膜攻击复合物和穿孔素）结构域具有显著同源性的结构域，这些补体成分和穿孔素蛋白参与动物的先天免疫。此外，在表达nahG（编码一种SA降解酶）的转基因cad1植物中，细胞死亡受到抑制。因此，我们得出结论，CAD1蛋白在植物免疫中负调控SA介导的程序性细胞死亡途径。
