Evolutionary, Molecular and Genetic Analyses of Tic22 Homologues in Arabidopsis thaliana Chloroplasts

PLoS One

Henrik Aronsson¹  Nadir Zaman Khan¹  Sazzad Karim¹  Qihua Ling²  Ramesh Patel²  Paul Jarvis²  Ali Reza Kasmati²  Mats Töpel² 

[1]University of Gothenburg, Department of Biological and Environmental Sciences, Gothenburg, Sweden

[2]University of Leicester, Department of Biology, Leicester, United Kingdom

关键词: Chloroplasts;    Arabidopsis thaliana;    Sequence analysis;    Amino acid sequence analysis;    Sequence alignment;    Phenotypes;    Plant genomics;    Phylogenetic analysis;   

DOI  :  10.1371/journal.pone.0063863

学科分类：医学（综合）

来源: Public Library of Science

【 摘 要 】

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.

【 授权许可】

CC BY