Submitted to: Journal of Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2000
Publication Date: N/A
Citation: N/A Interpretive Summary: Many plants become 'unstable' during growth and the symptoms are yellow or white sectors or leaves, flowers, or fruits. Sometimes this instability caused a small loss of part of the plants hereditary material. This loss or deletion may causes changes at the molecular level. In soybean we have identified a certain region in the plant's genetic material that is very unstable. Biochemical determinations indicate a loss or deletion of a small piece of genetic material. In the same area as the deletion, we have identified an unusual protein that might cause this instability. These deletions may result in beneficial but more likely detrimental effects on soybean growth and performance. This study will benefit soybean producers and consumers by providing vigorous soybean germplasm.
Technical Abstract: The mitochondrial malate dehydrogenase-1 (Mdh1) gene of soybean [Glycine max (L.) Merr.] spontaneously mutates to a null phenotype at a relatively high rate (Chen and Palmer, 1998). To determine the molecular basis for the instability of the Mdh1 gene, the gene was cloned and sequenced. The null phenotype correlated with the deletion of specific genomic restriction nfragments that encode the Mdh1 gene. The composition of the Mdh1 gene and its environs was compared with those of the more stable MDH 2 gene. Several possible causes of the observed instability were found, including duplications, repeats, and two regions with similarity to a soybean catalase. The most likely cause of instability, however, appeared to be a 1233-bp region with 58.9% identity to the Cyclops retrotransposons. Translation of a 714-bp segment of this region produced a peptide composed of 238 amino acid residues that showed 35 to 40% identity and 55 to 60% similarity to several putative Cyclops gag-pol proteins (group-specific antigen-polyprotein). This short peptide also contained a segment that corresponded to the protease active site of the gag-pol protein. Thus, in an appropriate genetic background, a retrotransposon, whether whole or fractured, could promote genetic rearrangements.