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Interallelic complementation at the ubiquitous urease coding locus of soybean.
Ariel Goldraij1, Lesa J Beamer, Joe C Polacco
1Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.
Plant Physiology
|August 13, 2003
Summary
Soybean mutant aj6 lacks leaf urease activity due to a specific genetic lesion. This study identifies aj6 and eu4 as mutations in the ubiquitous urease structural gene, revealing insights into urease function and compensation mechanisms.
Area of Science:
- Plant Molecular Biology
- Enzymology
- Genetics
Background:
- Soybean urease exists in embryo-specific and ubiquitous forms.
- Mutant aj6 exhibits absent ubiquitous urease activity in leaves and callus, with urea accumulation.
- Previous studies identified urease mutants at Eu1, Eu2, and Eu3 loci.
Purpose of the Study:
- To characterize the genetic basis of the soybean aj6 mutation.
- To determine if aj6 is an allele of known urease loci (Eu1-Eu3).
- To investigate the structural gene for ubiquitous urease and its relationship with mutant eu4.
Main Methods:
- Genetic crosses and segregation analysis (F1, F2 generations).
- Urease activity assays in various plant tissues.
- Cloning of ubiquitous urease coding sequences using reverse transcriptase-polymerase chain reaction (RT-PCR).
- Sequence analysis of open reading frames (ORFs) from wild-type and mutant plants.
Main Results:
- aj6 is not allelic to Eu1, Eu2, or Eu3 loci.
- aj6 mutation causes loss of ubiquitous urease activity in seeds.
- Crosses with eu4/eu4 (ubiquitous urease structural gene mutant) show heteroallelic interaction and partial urease activity restoration.
- aj6/aj6 ORF has an R201C substitution; eu4/eu4 ORF has a G468E substitution.
- Both aj6 and eu4 mutations affect the ubiquitous urease structural gene.
Conclusions:
- aj6 and eu4 are confirmed as mutants in the ubiquitous urease structural gene.
- Distinct amino acid substitutions in different domains can be partially compensated within the urease heterotrimer.
- The study elucidates the structural and functional aspects of soybean ubiquitous urease.