Amino acid residues conferring herbicide tolerance in tobacco acetolactate synthase
Amino acid residues conferring herbicide tolerance in tobacco acetolactate synthase
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DOI：
10.1006/bbrc.2000.3958
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发表时间：
2000-12-20
影响因子：
3.1
通讯作者：
Choi, JD
中科院分区：
文献类型：
--
作者：
Chong, CK;Choi, JD
乙酰乳酸合酶 (ALS) 是植物和微生物中缬氨酸、亮氨酸和异亮氨酸生物合成途径中的常见酶。 ALS 是几类结构上不相关的除草剂的靶位点，包括磺酰脲类、咪唑啉酮类和三唑并嘧啶类。为了鉴定烟草 ALS 中赋予除草剂耐受性的残基，对三个残基 Ala121、Pro187 和 Ser652 进行了定点诱变。突变体A121T对Londax（磺酰脲类）和Cadre（咪唑啉酮）表现出强抗性，而突变体S652T仅对Cadre具有抗性。 S652N突变消除了FAD的结合亲和力，并使该酶失活。 Ala121 和 Ser652 与 Thr 的双重突变产生了对 Londax、Cadre 和 TP（三唑并嘧啶磺酰胺）高度耐受的突变体，但具有与野生型相似的酶特性。用 Ser 取代 Pro187 导致该酶对氧化和断裂高度敏感。这些结果表明，两个残基Ala121和Ser652是赋予烟草ALS除草剂抗性的有效残基，并且Thr对Ala121和Ser652的双重突变可以赋予对Londax、Cadre和TP更强的耐受性。 (C) 2000 年学术出版社。
Acetolactate synthase (ALS) is the common enzyme in the biosynthetic pathways leading to valine, leucine, and isoleucine in plants and microorganisms. ALS is the target site of several classes of structurally unrelated herbicides including sulfonylureas, imidazolinones, and triazolopyrimidines. To identify the residues conferring herbicide tolerance in tobacco ALS, site-directed mutagenesis for three residues, Ala121, Pro187 and Ser652, was performed. Mutant A121T showed strong resistance to Londax (a sulfonylurea) and Cadre (an imidazolinone), while mutant S652T was resistant only to Cadre. The S652N mutation abolished the binding affinity of FAD, and inactivated the enzyme. Double mutation of Ala121 and Ser652 with Thr yielded a mutant highly tolerant to Londax, Cadre, and TP (a triazolopyrimidine sulfonamide), but has enzymatic properties similar to those of wild-type. Substitution of Pro187 with Ser resulted in the enzyme highly susceptible to oxidation and fragmentation. These results suggest that two residues Ala121 and Ser652 are potent residues conferring herbicide resistance in tobacco ALS, and that double mutation of Ala121 and Ser652 by Thr can confer stronger tolerance to Londax, Cadre, and TP. (C) 2000 Academic Press.