MITOCHONDRIAL GENOME DIVERSITY IN SOYBEAN - REPEATS AND REARRANGEMENTS

Mitochondrial (mt) genome organization in soybean was examined at the molecular level. This study builds upon previous reports that four soy bean cytoplasmic groups, Bedford, Arksoy, Lincoln, and soja-forage, ar e differentiated by polymorphisms detected with a 2.3 kb Hind III mtDN A probe [12]. The variation detected results from DNA alterations in a region within and around a 4.8 kb repeat. The Bedford-type cytoplasm is the only cytoplasm that contains copies of a 4.8 kb repeat in four different genomic environments, evidence that it is recombinationally active. The Lincoln- and Arksoy-type cytoplasms each contain two copie s of the repeat, as well as unique fragments that appear to result fro m rare recombination events outside, but near, the repeat. The soja-fo rage-type cytoplasm contains no complete copies of the repeat, but doe s contain a unique truncated version of the repeat. Sequence analysis indicates that the truncation is a result of recombination across a 9 bp repeated sequence, CCCCTCCCC. The structural rearrangements that ha ve occurred in the region surrounding the 4.8 kb repeat may provide a means to dissect species relationships and evolution within the subgen us soja.