Shevchik V E, Boccara M, Vedel R, Hugouvieux-Cotte-Pattat N
Laboratoire de Génétique Moléculaire des Microorganismes, UMR-CNRS 5577, INSA, Villeurbanne, France.
Mol Microbiol. 1998 Sep;29(6):1459-69. doi: 10.1046/j.1365-2958.1998.01028.x.
Erwinia chrysanthemi causes soft rot on various plants. The maceration of plant tissues is mainly due to the action of endopectate lyases. The E. chrysanthemi strain 3937 produces eight endopectate lyases (PelA, PelB, PelC, PelD, PelE, PelI, PelL and PelZ) that are secreted by the Out pathway. The necrotic response elicited by the wild-type E. chrysanthemi strain on tobacco leaves is due to an extracellular protein secreted by the Out machinery. Purification of the active factor revealed that it corresponds to a pectate lyase presenting immunological cross-reaction with PelI. Analysis of pelI and out mutants indicated that the necrosis-inducing pectate lyase results from a post-translational modification of PelI occurring extracellularly both in culture media and in planta. This modification consists of the cleavage of 97 N-terminal amino acids by the extracellular proteases of E. chrysanthemi. The enzymatic properties of the maturated form, PelI-3, are not, or only weakly, modified. However, this maturation gives rise to a small size and basic form that is active as a defence elicitor in plants.
菊欧文氏菌会在多种植物上引发软腐病。植物组织的浸解主要归因于内切果胶酸裂解酶的作用。菊欧文氏菌3937菌株可产生8种内切果胶酸裂解酶（PelA、PelB、PelC、PelD、PelE、PelI、PelL和PelZ），这些酶通过外排途径分泌。野生型菊欧文氏菌菌株在烟草叶片上引发的坏死反应是由外排机制分泌的一种细胞外蛋白所致。对活性因子的纯化表明，它对应一种与PelI呈现免疫交叉反应的果胶酸裂解酶。对pelI和外排突变体的分析表明，诱导坏死的果胶酸裂解酶是PelI在培养基和植物体内细胞外发生翻译后修饰的结果。这种修饰包括菊欧文氏菌的细胞外蛋白酶切割97个N端氨基酸。成熟形式的PelI-3的酶学性质未发生改变，或仅发生了微弱改变。然而，这种成熟产生了一种小尺寸的碱性形式，它作为植物中的防御激发子具有活性。
