TRYPTOPHAN MUTANTS IN ARABIDOPSIS - THE CONSEQUENCES OF DUPLICATED TRYPTOPHAN SYNTHASE BETA GENES
TRYPTOPHAN MUTANTS IN ARABIDOPSIS - THE CONSEQUENCES OF DUPLICATED TRYPTOPHAN SYNTHASE BETA GENES
复制标题
DOI：
10.1105/tpc.3.4.345
复制
发表时间：
1991-04-01
期刊：
影响因子：
11.6
通讯作者：
FINK, GR
中科院分区：
文献类型：
--
作者：
LAST, RL;BISSINGER, PH;FINK, GR
十字花科植物拟南芥有两个密切相关的非等位基因色氨酸合成酶-β基因(TSB1和TSB2)，每个基因都含有四个内含子和一个叶绿体前导序列。这两个基因都是转录的，尽管TSB1在叶组织中产生90%的色氨酸合成酶-βmRNA。一个需要色氨酸的突变体Trp2-1已被鉴定为具有约10%的野生型色氨酸合成酶-β活性。Trp2-1突变由TSB1转基因补充，并与TSB1基因的多态性有关，强烈表明Trp2-1是TSB1的突变。Trp2-1突变体是有条件的：它们在标准光照下生长需要色氨酸，但在非常弱的光照条件下不需要。据推测，在弱光下，低表达的基因TSB2能够支持生长。遗传冗余可能是植物中许多芳香族氨基酸生物合成酶的常见现象，因为另外两个基因(TRP1和TRP3)缺陷的突变体也表现出条件性色氨酸营养不良。两条色氨酸途径的存在对氨基酸和次生代谢物生物合成的组织特异性调控具有重要影响。
The cruciferous plant Arabidopsis thaliana has two closely related, nonallelic tryptophan synthase-beta-genes (TSB1 and TSB2), each containing four introns and a chloroplast leader sequence. Both genes are transcribed, although TSB1 produces > 90% of tryptophan synthase-beta mRNA in leaf tissue. A tryptophan-requiring mutant, trp2-1, has been identified that has about 10% of the wild-type tryptophan synthase-beta activity. The trp2-1 mutation is complemented by the TSB1 transgene and is linked genetically to a polymorphism in the TSB1 gene, strongly suggesting that trp2-1 is a mutation in TSB1. The trp2-1 mutants are conditional: they require tryptophan for growth under standard illumination but not under very low light conditions. Presumably, under low light the poorly expressed gene, TSB2, is capable of supporting growth. Genetic redundancy may be common to many aromatic amino acid biosynthetic enzymes in plants because mutants defective in two other genes (TRP1 and TRP3) also exhibit a conditional tryptophan auxotrophy. The existence of two tryptophan pathways has important consequences for tissue-specific regulation of amino acid and secondary metabolite biosynthesis.