Bergmann C W, Ito Y, Singer D, Albersheim P, Darvill A G, Benhamou N, Nuss L, Salvi G, Cervone F, De Lorenzo G
Complex Carbohydrate Research Center, University of Georgia, Athens 30602-4712.
Plant J. 1994 May;5(5):625-34. doi: 10.1111/j.1365-313x.1994.00625.x.
Polygalacturonase-inhibiting protein (PGIP) is a cell wall-associated protein that specifically binds to and inhibits the activity of fungal endopolygalacturonases. The Phaseolus vulgaris gene encoding PGIP has been cloned and characterized. Using a fragment of the cloned pgip gene as a probe in Northern blot experiments, it is demonstrated that the pgip mRNA accumulates in suspension-cultured bean cells following addition of elicitor-active oligogalacturonides or fungal glucan to the medium. Rabbit polyclonal antibodies specific for PGIP were generated against a synthetic peptide designed from the N-terminal region of PGIP; the antigenicity of the peptide was enhanced by coupling to KLH. Using the antibodies and the cloned pgip gene fragment as probes in Western and Northern blot experiments, respectively, it is shown that the levels of PGIP and its mRNA are increased in P. vulgaris hypocotyls in response to wounding or treatment with salicylic acid. Using gold-labeled goat-anti-rabbit secondary antibodies in EM studies, it has also been demonstrated that, in bean hypocotyls infected with Colletotrichum lindemuthianum, the level of PGIP preferentially increases in those cells immediately surrounding the infection site. The data support the hypothesis that synthesis of PGIP constitutes an active defense mechanism of plants that is elicited by signal molecules known to induce plant defense genes.
多聚半乳糖醛酸酶抑制蛋白（PGIP）是一种与细胞壁相关的蛋白，它能特异性结合并抑制真菌内切多聚半乳糖醛酸酶的活性。编码PGIP的菜豆基因已被克隆和鉴定。在Northern杂交实验中，用克隆的pgip基因片段作为探针，结果表明，向培养基中添加具有诱导活性的寡聚半乳糖醛酸或真菌葡聚糖后，悬浮培养的菜豆细胞中pgip mRNA会积累。针对从PGIP N端区域设计的合成肽产生了对PGIP特异的兔多克隆抗体；该肽与钥孔血蓝蛋白偶联后抗原性增强。分别用这些抗体和克隆的pgip基因片段作为探针进行Western杂交和Northern杂交实验，结果表明，菜豆下胚轴中PGIP及其mRNA的水平在受到创伤或用水杨酸处理后会升高。在电子显微镜研究中使用金标记的羊抗兔二抗，还证明了在感染菜豆炭疽菌的菜豆下胚轴中，PGIP水平在紧邻感染部位的那些细胞中优先升高。这些数据支持了这样一种假说，即PGIP的合成构成了植物的一种主动防御机制，该机制由已知能诱导植物防御基因的信号分子引发。
