A SINGLE-GENE (EU4) ENCODES THE TISSUE-UBIQUITOUS UREASE OF SOYBEAN

We sought to determine the genetic basis of expression of the ubiquito us (metabolic) urease of soybean. This isozyme is termed the metabolic urease because its loss, in eu4/eu4 mutants, leads to accumulation of urea, whereas loss df the embryo-specific urease isozyme does not. Th e eu4 lesion eliminated the expression of the ubiquitous urease in veg etative and embryonic tissues. RFLP analysis placed urease clone LC4 n ear, or within, the Eu4 locus. Sequence comparison of urease proteins (ubiquitous and embryo-specific) and clones (LC4 and LS1) indicated th at LC4 and LS1 encode ubiquitous and embryo-specific ureases, respecti vely. That LC4 is transcribed into poly(A)(+) RNA in all tissues was i ndicated by the amplification of its transcript by an LC4-specific PCR primer. (The LS1-specific primer, on the other hand, amplified poly(A )(+) RNA only from developing embryos expressing the embryo-specific u rease.) These observations are consistent with Eu4 being the ubiquitou s urease structural gene contained in the LC4 clone. In agreement with this notion, the mutant phenotype of eu4/eu4 callus was partially cor rected by the LC4 urease gene introduced by particle bombardment.