Biochemical and molecular characterization of a rice glutelin allele for the GluA-1 gene

The rice (Oryza sativa L.) mutant of glu4a, lacking the glutelin α-2 subunit while the α-1 subunit increased (α-1H/α-2L), was used in this study. Two-dimensional electrophoresis analysis revealed that the mutant lacked the polypeptide pI6.71/α-2 encoded by glu4 while forming a new polypeptide of pI6.50/α-1. Experiments were conducted to identify the relationships between the mutated polypeptides of the mutant and to illustrate the mutation mechanism of the allele. Peptide mapping and amino-acid sequence analyses revealed that the newly formed glu4a encoded polypeptide pI6.50/α-1 of high homology with the deleted pI6.71/α-2 polypeptide which was encoded by glu4 (GluA-1). The nucleotide sequence revealed that the iso-electric point variation of the pI6.50/α-1 polypeptide was caused by a point mutation with nucleotide replacement at the variable region of the gene. These results suggested the possibility of altering glutelin quality by using single gene mutation.