Character Identification And Genetic Analysis In Rice Endosperm Storage Protein Of Novel57H Mutants

Rice seed, the important resource of protein, is widely utilized in various yields. Glutelins and prolamins are the major proteins in rice seed. Glutelins are synthesized in the ER as57kDa precursor,, transferred to the vacuole through or bypassing the Golgi body, cleaved into the mature types of40kDa acidic and20kDa basic components, and eventually accumulated into the vacuolar protein body;13-14kDa prolamins are synthesized, and deposited into the ER-derived protein body in endosperm cell of the developing rice seed. The storage proteins are greatly responsible for the quality of rice proteins.57H mutants with the high amounts of glutelin precursor are useful genetic materials for studying mechanism concerning synthesis and accumulation of the storage proteins in rice. Four57H mutations resulting in the remarkable decrease of the mature glutelins have been involved in the storage protein accumulation. However, overall understanding of genetic mechanism concerning synthesis and accumulation of the storage proteins is a long-term systematic project, it is necessary to develop and analyze more diverse57H mutant.In the preliminary study in this laboratory, series of mutants with the high amounts of57kDa polypeptide were newly obtained from490rice germplasms.4mutants of them showed the obvious increase of57kDa polypeptide, in comparison with the wild type cultivar (Liaoyan6). In this study,2mutants of them were confirmed to have inheritable characters of both the57kDa polypeptide increase and the lack of13kDa polypeptide, the third mutant only showed the inheritable character of the57kDa polypeptide increase, the fourth mutant showed the inheritable character of the57kDa polypeptide increase and the remarkable decrease of40kDa and20kDa polypeptide, based on these, they are named as gph1, gph2, Gph3, gph4, respectively; SDS-PAGE and immunoblotting analyses of seed storage proteins showed the glutelins precursor increase and lack of13kDa prolamins in gphland gph2, the glutelin precursor increase in Gph3, and the remarkable decrease of the mature glutelins following the glutelin precursor increase in gph4, the results indicate that gphl, gph2and Gph3have the novel characters distinct with the reported57H mutant characters; To explore novel genetic information for57H mutation, genetic analysis was performed analyzing SDS-PAGE phenotypes of storage proteins in F1and F2seeds from the crossed between each of the novel mutants and each of the Liaoyan6and reported57H mutants, the results show that the gphl and Gph3characters result from mutation of a novel non-allelic gene, respectively, the former mutation is dominant and the latter mutation have dosage effect on the glutelin precursor increase. The two genes could concern regulation of synthesis and expression of the storage proteins, and affect accumulation state of the proteins. Positional cloning and functional analysis of the genes is expected to promote the overall understanding of genetic mechanism regulating synthesis and accumulation of storage proteins and the achieving of breeding objective for diversification of quality of rice proteins.