摘要： 植物先天免疫的分子基础是位于植物细胞膜的受体蛋白对病原菌特有分子模式的特异识别。脂多糖（LPS）是革兰氏阴性菌细胞壁的核心组分，可以被动物细胞质膜的TLR4复合物识别。为了探索植物细胞识别LPS的受体，用动物TLR4氨基酸序列比对拟南芥蛋白数据库，发现拟南芥AtGHR1氨基酸序列同TLR4高度类似。利用β-葡萄糖苷酸酶（GUS）报告基因和绿色荧光蛋白标记技术，发现AtGHR1在叶片和根尖中强表达，其编码蛋白位于细胞质膜。在AtGHR1基因缺失突变体atghr1叶子上，含有LPS的病原菌Pst DC3000繁殖的数量显著高于在拟南芥野生植物叶子上的数量，说明atghr1比野生植物更感病。LPS处理诱导H₂O₂和细胞质Ca²⁺浓度的升高，但是在拟南芥野生植物和突变体atghr1幼苗之间没有显著性区别。在atghr1突变体保卫细胞内，利用NO荧光探针对LPS诱导的NO爆发进行实时检测，发现NO依赖的荧光信号显著低于野生植物。转录组芯片研究发现，在表达水平上受LPS调控的基因中，有部分依赖AtGHR1的存在。这些数据表明，AtGHR1是拟南芥感应LPS必需基因，部分参与拟南芥对LPS的先天免疫反应；在AtGHR1以外，还有其他未知基因参与这一过程。

关键词: 拟南芥, 脂多糖, 先天免疫, AtGHR1

Abstract: Molecular basis of plant innate immunity depends on specific recognization of pathogen specific molecular pattern by the plant plasma membrane localized receptor. Lipopolysaccharide (LPS) is a core component within cell walls of Gram-negative bacteria and is perceived by the Toll-Like Receptor4 (TLR4) complex in the plasma membrane of animal cells. By searching Arabidopsis protein database with TLR4 amino acid sequence, we found that in Arabidopsis AtGHR1 had the highest amino acid sequence similarity with human TLR4. With GUS and green fluorescent protein labeling techniques, AtGHR1 had high expression in the leaf and root tip and its protein localizes in the plasma membrane. LPS containing bacterial pathogen Pst DC3000 had significant higher growth on the atghr1 gene knock out mutant than that on the wild type. It implied that atghr1 was more susceptible to the pathogen than the wild type. There was no significant difference between wild type and atghr1 of the LPS induced H₂O₂ and cytosolic Ca²⁺ rise. With NO fluorescent probe, it was found that LPS-induced NO generation was much weaker in the atghr1 than that in wild type. With transcriptional microarray, a part of LPS-regulated gene expression was dependent on AtGHR1. These data demonstrated that AtGHR1 was one of necessary genes for plant cell sensing LPS and partially took part in the Arabidopsis innate immunity response to LPS;there are other unknown genes involved in this process.

Key words: Arabidopsis, Lipopolysaccharide, Innate immunity, AtGHR1

中图分类号: 

• S432.03

• Q78