THE TRANSKETOLASE GENE FAMILY OF THE RESURRECTION PLANT CRATEROSTIGMA-PLANTAGINEUM - DIFFERENTIAL EXPRESSION DURING THE REHYDRATION PHASE
THE TRANSKETOLASE GENE FAMILY OF THE RESURRECTION PLANT CRATEROSTIGMA-PLANTAGINEUM - DIFFERENTIAL EXPRESSION DURING THE REHYDRATION PHASE
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DOI：
10.1002/j.1460-2075.1995.tb07037.x
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发表时间：
1995-02-01
期刊：
影响因子：
11.4
通讯作者：
BARTELS, D
中科院分区：
文献类型：
--
作者：
BERNACCHIA, G;SCHWALL, G;BARTELS, D
转酮醇酶是戊糖磷酸还原和氧化途径的关键酶，负责糖磷酸中间体的合成。在这里，我们报告的第一个转酮醇酶基因的分子分析植物。从耐脱水复苏植物Craterostigma plantagineum中分离出三类不同的转酮醇酶编码cDNA克隆。一类由转录本tkt 3代表的组成型表达在所有测试的生理条件下的叶和根。通过对纯化的转酮醇酶的生化分析和蛋白质测序，表明tkt 3以三种酶活性异构体表达。一个有趣的发现是，其他两个转酮醇酶的转录本，tkt 7和tkt 10的积累，优先与脱水植物的复水过程;而tkt 10只在叶中表达，tkt 7检测到在叶和根。这一观察结果表明，这些转酮酶在糖的转化中可能起作用，糖的转化是再水化过程中的主要现象。尽管在复水叶中有丰富的tkt 7和tkt 10转录本，但不能分离出蛋白质。这部分是由于翻译控制机制作用于mRNA向多核糖体的加载。
Transketolases, key enzymes of the reductive and oxidative pentose phosphate pathways, are responsible for the synthesis of sugar phosphate intermediates. Here we report the first molecular analysis of transketolase genes from plants. Three distinct classes of transketolase-encoding cDNA clones were isolated from the desiccation-tolerant resurrection plant Craterostigma plantagineum. One class represented by the transcript tkt3 is constitutively expressed in leaves and roots under all physiological conditions tested. By biochemical analysis and protein sequencing of purified transketolase, it was shown that tkt3 is expressed in three enzymatically active isoforms. An intriguing discovery was that accumulation of the two other transketolase transcripts, tkt7 and tkt10, is preferentially associated with the rehydration process of the desiccated plant; whereas tkt10 is only expressed in leaves, tkt7 was detected in leaves and roots. This observation suggests a possible role for these transketolases in the conversion of sugars, which are a major phenomenon in the rehydration process. Despite an abundant level of tkt7 and tkt10 transcripts in rehydrating leaves, proteins could not be isolated. This is due in part to a translational control mechanism acting on the loading of mRNAs to polysomes.