Evidence that the two sucrose synthetase genes in maize are related

Summary Evidence is presented that the sucrose synthetase coding sequence at the Shrunken locus is distantly related to the sequence encoding a second, minor sucrose synthetase present in maize endosperm. Three doubly mutant sh bz strains lacking at least part of the Sh coding sequence produce an antigenically cross-reactive protein having the same electrophoretic mobility as the Sh-encoded, 92-kD sucrose synthetase monomer, but differing in primary structure. An mRNA is present in endosperm of mutants with deletions at the Sh locus that is weakly homologous to the Sh coding sequence and encodes a 92-kD protein precipitable with antiserum to sucrose synthetase. We conclude that the genes encoding the two different proteins are related.