Diversity of Phenotypes of Endosperm Storage Proteins of Rice 57H Mutants and Their Classification

Seed storage proteins are mainly composed of glutelins, prolamins and globulins. The proteins are synthesized and compartmented during seed development. Compartmentation of the proteins results in their accumulation. This study was performed to present a novel perspective for overall understanding of genetic mechanism regulating the protein compartmentation in rice endosperm. SDS-PAGE and immunoblot analyses of the storage proteins showed that rice 57H mutants containing the high amount of 57kD glutelin precursor had the various phenotypes of endosperm storage proteins, in comparison with the wild type of cultivar. The mutants were classified into 3 types on the basis of the diversity of their phenotypes. The typeⅠ of glup4, glup6, Glup5 and esp2 mutants all showed not only the deposition of the glutelin precursor and the inhibited deposition of the mature types of 40kD and 20kD glutelin subunits, but also the decreased depositions of 26kD globulin and b species of 13kD prolamins. The type Ⅱ of Glup1 and glup2 mutants showed the decreased depositions of 26kD globulin in addition to the glutelin precursor deposition. The type Ⅲ of glup3 mutant only showed the glutelin precursor deposition following the inhibited deposition of the glutelin subunits. These results indicate that 57H mutations have various effects on the accumulation of the storage proteins, and thus are the essentially genetic systems concerning the protein compartmentation. The possible effects of the genetic systems on the post-translational compartmentation and nutritional properties of rice storage proteins are discussed in this paper.