Rice glutelins consist of acidic (α) and basic (β) subunits which are further separated into three polypeptide components assigned as α-1, α-2, and α-3 sub-unit components and β-1, β-2 and β-3 subunit components. Nine rice mutant lines with a decreased amount of the glutelin α-2 subunit component (α-2L) were obtained by screening about 6,800 potential mutant lines derived from the fertilized egg treatment with N-methyl-N-nitrosourea (MNU) using the SDS-PAGE method. The mutants were classified into three types of the increased α-1 subunit (α-1H/α-2L), the decreased β-2 subunit (β-2L/α-2L) and the increased α-3 subunit (α-3H/α-2L) represented by EM278, CM1707 and EM659, respectively. Iso-electric focus (IEF) analysis revealed that all of the mutants had an extremely low amount of a polypeptide with a 6.71 pI value, whereas a polypeptide with either a 6.50 pI value or with a 6.90 pI value increased significantly in α-1H/α-2L mutants or in α-3H/α-2L mutants, respectively. The β-2L/α-2L mutants had a decreased amount of a basic polypeptide with a 8.74 pI value. Genetic analysis revealed that the three types of mutants were controlled by a single incomplete dominant gene respectively, and the three are alleles. The gene was temporarily named glu4, which was found to be located on chromosome 1 linked with the eg and spl6 genes. Two-dimensional electrophoresis analysis revealed that the glu4 encoded polypeptides of pI 6.71/α-2 and pI 8.74/β-2. Amino acid sequence analysis suggested that the mutated acidic polypeptide was the product of a GluA subfamily gene. Northern and RT-PCR analyses revealed that glu4 corresponded to the GluA-1 gene.
All Science Journal Classification (ASJC) codes
- Agronomy and Crop Science