Analysis of rice mitochondrial genome organization using
pulsed-field gel electrophoresis

P Senthilkumar  and  K K Narayanan*,†

Centre for Biotechnology, SPIC Science Foundation, 111, Mount View, Mount Road, Chennai 600 032, India
†Present address: Monsanto/IISc R and D Centre, INBRI First Floor, No. 277, Chowdaiah Road,
18th Cross, Malleswaram, Bangalore 560 003, India

*Corresponding author (Fax, 91-80-344 4452; Email, narayanan61@hotmail.com).

Most of the plant mitochondrial (mt) genomes that have been mapped are believed to be organized as master circle molecules from which sub-genomic molecules arise through homologous recombination. We have
evidence to suggest that a major part of the rice mt genome is organized as independent, sub-genomic molecules or mt chromosomes, one of which has already been mapped. This study is aimed at the identification of the other molecular entities that comprise the genome.

Pulsed-field gel electrophoresis of the native rice mt DNA and Southern analysis with different mt gene probes have shown that in addition to the 117 kb mt chromosome, at least four more such molecules of sizes 130 kb, 95  kb, 70 kb and 56 kb account for most of the rice mt genome. A majority of the rice mt genes that encode products involved in oxidative phosphorylation are distributed among these five chromosomes. Partial restriction map of the 95 kb orf 25/cox 3 chromosome, indicating the sites for the enzymes BglII and HindIII has also been determined.

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