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Abstract Detail


Protein Targeting and Vesicular Trafficking

Zhong, Rong [1], Thompson, Jennifer [2], Lamppa, Gayle [2].

Characterization of A Chloroplast Import Deficient Mutant cid4.

We have developed a novel transgene-based genetic screen in Arabidopsis thaliana to explore the regulation and specificity of protein transport into the chloroplast. A parental plant line expressed transgenes for an herbicide resistant form of 5-enolpyruvylshikimate 3-phosphate synthase (EPSP*) and GFP fused to a ferredoxin transit peptide. Because EPSP*, a key enzyme in shikimate pathway, is imported into the chloroplast to perform its function, a loss of efficient import of EPSP* leads to herbicide sensitivity. Using the two reporters, our screen has identified six chloroplast import deficient (cid) mutants, induced by EMS, showing a loss of herbicide tolerance and GFP mislocalization to the nucleus. We chose cid4 for characterization because it is due to a single recessive mutation and exhibits a strong phenotype. In soil, cid4 displayed dark leaves, small stature, delayed growth, and reduced silique number. Leaf cells of cid4 were disorganized and rounded with large vacuoles and more intercellular space. cid4 chloroplasts had more grana stacks, starch granules and lipid droplets than wild type. On MS media without sucrose, 90% of the cid4 plants exhibited retarded growth and died. In contrast, wild-type plants survived. The mutation was mapped to the north arm of chromosome I between markers F16J7-TRB and M59, an interval of 2,027 kb. The known proteins of Toc and Tic (outer and inner translocons), SPP and TPP (chloroplast peptidases) and cia2 (transcription factor) are not located in the cid4 mutation region, indicating that the loss of efficient import is due to an unknown step or component, yet to be defined. Identification of the cid4 gene and phenotypic characterization will broaden our understanding of the mechanism of protein import.


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1 - The University of Chicago, Department of Molecular Genetics and Cell Biology, 920 E. 58th St., Chicago, IL, 60637, USA
2 - The University of Chicago, Department of Molecular Genetics and Cell Biology

Keywords:
chloroplast protein transport.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P22018
Abstract ID:603


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