Evolutionary, molecular and genetic analyses of Tic22 homologues in Arabidopsis thaliana chloroplasts.
Evolutionary, molecular and genetic analyses of Tic22 homologues in Arabidopsis thaliana chloroplasts.
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DOI：
10.1371/journal.pone.0063863
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Jarvis P
中科院分区：
文献类型：
--
作者：
Kasmati AR;Töpel M;Khan NZ;Patel R;Ling Q;Karim S;Aronsson H;Jarvis P
Tic 22蛋白先前在豌豆中被鉴定为叶绿体蛋白输入装置的推定组分。它是一种位于内膜的外周蛋白，位于膜间隙。在拟南芥中，有两个Tic 22同源物，称为atTic 22-III和atTic 22-IV，两者都被预测定位于叶绿体中。这两种蛋白质定义了在所有陆地植物中保守的进化枝，它们似乎自4亿年前分离以来以相似的速度进化，表明功能保守。atTIC 22-IV基因的表达比atTIC 22-III高几倍，但基因表现出相似的表达谱，并在整个发育过程中表达。缺乏atTic 22-IV的敲除突变体明显正常，而缺乏atTic 22-III的那些表现出中度失绿。缺乏这两种亚型的双突变体更强烈的褪绿，特别是在早期发展，但可行的和肥沃的。双突变体的叶绿体小，相对于野生型欠发达，并显示出低效的前体蛋白的进口。这些数据表明，这两个Tic 22异构体在叶绿体蛋白输入中起冗余作用，并且它们的功能是非必需的，但仍然是正常叶绿体生物发生所必需的，特别是在植物发育早期。
The Tic22 protein was previously identified in pea as a putative component of the chloroplast protein import apparatus. It is a peripheral protein of the inner envelope membrane, residing in the intermembrane space. In Arabidopsis, there are two Tic22 homologues, termed atTic22-III and atTic22-IV, both of which are predicted to localize in chloroplasts. These two proteins defined clades that are conserved in all land plants, which appear to have evolved at a similar rates since their separation >400 million years ago, suggesting functional conservation. The atTIC22-IV gene was expressed several-fold more highly than atTIC22-III, but the genes exhibited similar expression profiles and were expressed throughout development. Knockout mutants lacking atTic22-IV were visibly normal, whereas those lacking atTic22-III exhibited moderate chlorosis. Double mutants lacking both isoforms were more strongly chlorotic, particularly during early development, but were viable and fertile. Double-mutant chloroplasts were small and under-developed relative to those in wild type, and displayed inefficient import of precursor proteins. The data indicate that the two Tic22 isoforms act redundantly in chloroplast protein import, and that their function is non-essential but nonetheless required for normal chloroplast biogenesis, particularly during early plant development.
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