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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Dual targeting properties of the N-terminal signal sequence of Arabidopsis thaliana THI1 protein to mitochondria and chloroplasts

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Author(s):
Chabregas, Sabrina M. ; Luche, Douglas D. ; Farias, Leonardo P. ; Ribeiro, Alberto F. ; Van Sluys, Marie-Anne ; Menck, Carlos F. M. [6] ; Silva-Filho, Marcio C. [7]
Total Authors: 7
Document type: Journal article
Source: Plant Molecular Biology; v. 46, n. 6, p. 639-650, 2001.
Field of knowledge: Biological Sciences - Biochemistry
Abstract

Thi1 has been recently isolated from Arabidopsis thaliana and is probably involved in both thiamine biosynthesis and as protection of organellar DNA from damage. Studies of thiamine biosynthesis in plants suggests a plastid location for the pathway, which is in agreement with the predicted THI1 N-terminal chloroplastic transit peptide (TP). On the other hand, thiamine is synthesized in mitochondria in yeast cells. Interestingly, A. thaliana thi1 cDNA complements a yeast strain disrupted for the homologous gene. Analysis of THI1 amino acid sequence revealed the presence of a putative amphiphilic -helix, which is typical for mitochondrial presequences, located downstream of the chloroplast transit peptide. To define the putative role of the two predicted targeting sequences in tandem, we produced two chimeric genes encompassing the chloroplastic THI1 TP and either 4 or 27 (including the putative mitochondrial presequence) N-terminal residues of the mature THI1, both linked to the reporter (gusA) gene. Analysis of GUS distribution in subcellular fractions of transgenic plants revealed that in the construct retaining only 4 residues of mature THI1, GUS was found in the chloroplastic fraction. Extension of the THI1 transit peptide to 27 residues of the mature protein allowed import and processing of GUS into both mitochondria and chloroplasts. Direct analysis by immunogold-labeling with an anti-THI1 polyclonal antibody identified THI1 in both organelles in Arabidopsis. We also provide evidence that the precursors of both organellar isoforms are encoded by a single nuclear transcript. Thus, THI1 is targeted simultaneously to mitochondria and chloroplasts by a post transcriptional mechanism. (AU)

FAPESP's process: 98/11119-7 - Repair of damaged DNA and biological consequences
Grantee:Carlos Frederico Martins Menck
Support Opportunities: Research Projects - Thematic Grants