Royal Society Publishing

Recombination is Associated with Polymorphism of the Mitochondrial Genomes of Maize and Sorghum

D. R. Pring, B. G. Gengenbach, R. P. Wise

Abstract

Extensive recombination events characterize higher-plant mitochondrial DNAs. Numerous recombination events resulted in the appearance of an unusual mitochondrial open reading frame, urf13-T, which encodes a 13 kDa polypeptide in the male-sterile T cytoplasm of maize. Maize lines with T cytoplasm are unusually susceptible to two fungal pathogens which produce host-selective toxins. Mutants derived from tissue culture expressing male fertility and toxin-insensitivity are characterized by truncation or deletion of urf13-T. These events result from a frameshift associated with a tandem 5 base pair repeat, placing a premature stop codon in frame, or from a recombination event, apparently limited to tissue culture, resulting in the deletion of urf13-T. Neither class of mutants produces the 13 kDa gene product. Repeated sequences that participate in recombination in sorghum appear to be randomly distributed among male-fertile or male-sterile cytoplasms. Processes involved in the evolution of mitochondrial DNAs in higher plants therefore include the generation and deletion of configurations through recombination.

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