title: Interallelic complementation at the ubiquitous urease coding locus of soybean.
abstract: Soybean (Glycine max [L.] Merrill) mutant aj6 carries a single recessive lesion, aj6, that eliminates ubiquitous urease activity in leaves and callus while retaining normal embryo-specific urease activity. Consistently, aj6/aj6 plants accumulated urea in leaves. In crosses of aj6/aj6 by urease mutants at the Eu1, Eu2, and Eu3 loci, F(1) individuals exhibited wild-type leaf urease activity, and the F(2) segregated urease-negative individuals, demonstrating that aj6 is not an allele at these loci. F(2) of aj6/aj6 crossed with a null mutant lacking the Eu1-encoded embryo-specific urease showed that ubiquitous urease was also inactive in seeds of aj6/aj6. The cross of aj6/aj6 to eu4/eu4, a mutant previously assigned to the ubiquitous urease structural gene (R.S. Torisky, J.D. Griffin, R.L. Yenofsky, J.C. Polacco [1994] Mol Gen Genet 242: 404-414), yielded an F(1) having 22% +/- 11% of wild-type leaf urease activity. Coding sequences for ubiquitous urease were cloned by reverse transcriptase-polymerase chain reaction from wild-type, aj6/aj6, and eu4/eu4 leaf RNA. The ubiquitous urease had an 837-amino acid open reading frame (ORF), 87% identical to the embryo-specific urease. The aj6/aj6 ORF showed an R201C change that cosegregated with the lack of leaf urease activity in a cross against a urease-positive line, whereas the eu4/eu4 ORF showed a G468E change. Heteroallelic interaction in F(2) progeny of aj6/aj6 x eu4/eu4 resulted in partially restored leaf urease activity. These results confirm that aj6/aj6 and eu4/eu4 are mutants affected in the ubiquitous urease structural gene. They also indicate that radical amino acid changes in distinct domains can be partially compensated in the urease heterotrimer.
authors.affiliation: Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.
authors.forename: Ariel
authors.initials: A
authors.lastname: Goldraij
authors.forename: Lesa J
authors.initials: LJ
authors.lastname: Beamer
authors.forename: Joe C
authors.initials: JC
authors.lastname: Polacco
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D021902:Enterobacter aerogenes / Q000201:enzymology; D005816:Genetic Complementation Test; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D011487:Protein Conformation; D016415:Sequence Alignment; D013025:Glycine max / Q000201:enzymology* / Q000235:genetics*; D014508:Urea / Q000378:metabolism; D014510:Urease / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D014508:Urea; D014510:Urease