A point mutation in the ethylene-inducing xylanase elicitor inhibits the β-1-4-endoxylanase activity but not the elicitation activity
A point mutation in the ethylene-inducing xylanase elicitor inhibits the β-1-4-endoxylanase activity but not the elicitation activity
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DOI：
10.1104/pp.121.2.345
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发表时间：
1999-10-01
期刊：
影响因子：
7.4
通讯作者：
Avni, A
中科院分区：
文献类型：
--
作者：
Furman-Matarasso, N;Cohen, E;Avni, A
乙烯诱导的木聚糖酶（EIX）在某些烟草（Nicotiana tabacum）和番茄栽培品种中除了其木聚糖降解活性之外还增强植物防御反应。然而，目前尚不清楚诱导是通过酶活性释放的细胞壁片段还是通过木聚糖酶蛋白直接与植物细胞相互作用而发生的。我们克隆了编码EIX蛋白的基因，并在昆虫细胞中过表达。为了确定两种活性之间的关系，进行木聚糖酶活性位点中的氨基酸取代。用谷氨酰胺（Gln）、天冬氨酸（Asp）或甘氨酸（Cly）取代谷氨酸-86或-177抑制β-1-4-内切木聚糖酶活性。具有Asp-86或Gln-177的突变体也丧失了诱导过敏反应和乙烯生物合成的能力。然而，具有Gln-86、Gly-86、Asp-177或Gly-177的突变体保留了诱导乙烯生物合成和过敏反应的能力。我们的数据表明，EIX激发子的木聚糖酶活性可以从激发过程中分离出来，因为一些突变体缺乏前者，但保留了后者。
Ethylene-inducing xylanase (EIX) elicits plant defense responses in certain tobacco (Nicotiana tabacum) and tomato cultivars in addition to its xylan degradation activity. It is not clear, however, whether elicitation occurs by cell wall fragments released by the enzymatic activity or by the xylanase protein interacting directly with the plant cells. We cloned the gene encoding EIX protein and overexpressed it in insect cells. To determine the relationship between the two activities, substitution of amino acids in the xylanase active site was performed. Substitution at glutamic acid-86 or -177 with glutamine (Gln), aspartic acid (Asp), or glycine (Cly) inhibited the beta-1-4-endoxylanase activity. Mutants having Asp-86 or Gln-177 also lost the ability to induce the hypersensitive response and ethylene biosynthesis. However, mutants having Gln-86, Gly-86, Asp-177, or Gly-177 retained ability to induce ethylene biosynthesis and the hypersensitive response. Our data show that the xylanase activity of EIX elicitor can be separated from the elicitation process, as some of the mutants lack the former but retain the latter.