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Title: Targeted overexpression of the Escherichaia coli MinC protein in higher plants results in abnormal chloroplasts

Author
item TAVVA, VENKATA - UNIV. OF KENTUCKY
item COLLINS, GLENN - UNIV. OF KENTUCKY
item Dinkins, Randy

Submitted to: Molecular Genetics and Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2004
Publication Date: 4/1/2006
Citation: Tavva, V.S., Collins, G.B., Dinkins, R.D. 2006. Targeted overexpression of the Escherichaia coli MinC protein in higher plants results in abnormal chloroplasts. Molecular Genetics and Genomics. 25:314-348.

Interpretive Summary: One of the goals of this work has been to identify some of the genes involved in chloroplast development. It is now an accepted hypothesis that plastids arose through endosymbiosis between a cyanobacterial ancestor and an eukaryotic host cell. We, and others, have shown that chloroplast division utilizes some of the same type of proteins that are required in prokaryotic cell division, including proteins similar to the min operon in bacteria, namely the MinD and MinE proteins. Noticeably absent from the completed annotated genome of the higher plant Arabidopsis thaliana is a MinC homologue of the min operon. We sought to determine whether the bacterial MinC could interact with the higher plant chloroplast division machinery and specifically disrupting chloroplast division. The results indicate that over expression of the bacterial MinC proteins results in abnormal chloroplast development, suggesting that a functional MinC homologue should be present in the higher plant genome.

Technical Abstract: Higher plant chloroplast division utilizes some of the same type of proteins that are required in prokaryotic cell division, including proteins similar to the min operon in bacteria, namely the MinD and MinE proteins. Noticeably absent from the completed annotated genome of the higher plant Arabidopsis thaliana is a MinC homologue of the min operon. A higher plant functional MinC homologue that would interfere with FtsZ polymerization, has yet to be identified. We sought to determine whether the bacterial MinC could interact with the higher plant chloroplast division machinery and specifically disrupting chloroplast division. The Escherichia coli MinC gene was isolated and inserted behind the Arabidopsis thaliana rbcS transit peptide sequence for chloroplast targeting. This TP-EcMinC gene was then transformed into Arabidopsis and tobacco driven by the CaMV 35S2 constitutive promoter. Of the more than fifty Arabidopsis and tobacco transgenic plants analyzed, over eighty percent did not display any abnormal chloroplast morphology, however abnormally large chloroplasts were observed in the remainder of the plants. Unlike the mechanism observed in bacteria where inhibition of cell division by MinC is concentration dependent, expression levels, as measured by northern blots and quantitative real-time RT-PCR, were not directly correlated with the abnormal phenotypes. Transgene silencing also did not appear to cause the differential phenotypes, although post-transcriptional or translational regulation cannot be ruled out. Our results suggest that a functional MinC homologue should be present in the higher plant genome. .