Protein targeting into mitochondria in tobacco BY-2 cell visualized by green fluorescent protein (GFP). Red color: fluorescence of mitochondrial-specific dye. Yellow color: merged image of fluorescences from GFP and the mitochondrial-specific dye. Scale bar = 50um. (This work is the collaboration with Lab. Plant Mol. Genet., Univ. Tokyo and Lab. Mol. Biodiversity, Natl. Inst. Agrobiol. Sci.)

Prof. Dr. Nakao Kubo

Graduate School of Life and Environmental Sciences, Kyoto Prefectural University

Biotechnology Research Department, Kyoto Prefectural Agriculture, Forestry and Fisheries Technology Center
74 Oji, Kitainayazuma, Seika, Soraku,
Kyoto 619-0244, JAPAN
Fax: +81-774-93-3528
E-mail: nkubo kpu.ac.jp

As you may know, "MITOCHONDRION" is one of the cellular organelles, whose
main role is production of energy by oxidative phosphorylation. According to the
endosymbiont hypothesis, this organelle is thought to be derived from some symbiotic
bacteria which were entered into the host cell.

Current mitochondria have original genome, so-called "mitochondrial genome" or
"mitochondrial DNA". However, there are limited number of genes and most
mitochondrial proteins are encoded by the nuclear genes. It has been proposed that
these nuclear-encoded mitochondrial genes have been transferred from the
mitochondria to the nucleus during evolution. In general, the nuclear-encoded
genes have targeting signals which are involved in protein import to the mitochondrial
compartment. However, the origin and the mechanism of acquisition of these
targeting signals are not clearly understood.

In order to elucidate this question, we have been searching the nuclear genes which
had been transferred from the mitochondrion to the nucleus in relatively recent past.
To date, we have isolated a number of genes from the nuclear genomes in higher
plants, determined the origin of the targeting signals, and proposed mechanisms to
explain their acquisition.

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