Study On Protein Components And Microstructure Of The Japonica Restorer Line M119with High Protein Content

Protein content is the important factor in rice nutritional quality. Increasing protein content and improving nutritional quality of rice is one of the most important breeding objectives. By cross-breeding and screened through many generations, a, japonica restorer line （named m119） with extremely high protein content （the highest in japonica restorer line） was bred successfully, whose protein content （wet base） reached13.30%in brown rice and12.32%in milled rice. In order to reveal the differences between high protein cultivars and common ones, m119was investigated in the aspects of protein components, nutritional quality, specific protein, microstructure, functional factors, and compared with its Sib-line m90and famous japonica rice-Koshihikari in the aspects mentioned above, which provided valid data for developing high-protein rice products and protein quality breeding.By the analysis of Kjeldahl and SDS-PAGE, we concluded that the increased protein in m119mostly accumulated in milled rice, which suggested that the increase of protein content was neither proportion nor synchronization in rice grain; ml19possessed high proportion of glutelin fraction which riches in lysine, and have a more balanced ratio of amino acid.Hypothetical protein Os1₂7675, Os08g0127900and early embryogenesis protein were identified by mass spectrometry in m119specific protein associated with high-protein traits, and our results demonstrated that these proteins indeed existed in m119embryo, and the sequences were similar with globulin in other species, as well as the function.A specific band was observed in restorer line in SDS-PAGE patterns, which can be used as label for restorer gene, and based on the label, a new breeding method called’half grain’was established originally, which can remarkably shorten the breeding cycle and reduce the breeding cost.The cross-sections of brown rice were observed by SEM and CLSM, although the significant difference between the three varieties in protein content, there was no significant difference of endosperm cell in size, shape and distribution. However the aleurone layer in back of the grain was becoming thicker with the increasing of the protein content, the distribution density of protein body was positive correlated with the protein content in rice grain, compound starch granules in m119were surrounded by a large number of protein body.The eating quality of Koshihikari, m90and m119were successively decreasing identified by sensory evaluation and RVA pasting profile, but all the three were better than market rice. Further study about the impact of protein on the rice cooking and eating quality, from CLSM images of soaked grain fracture, the three cultivars with different protein contents also varied in fracture roughness, the higher the protein content was, the rougher the fracture was, which meant less water was absorbed and indirectly reflected the cooking quality. Microstructure of the cooked rice was observed by SEM and CLSM, the compound starch granules in m119were surrounded by a large number of honeycomb-like protein body, which limited the absorption and gelatinization of starch granules and eventually led to the reduce of cooking and eating quality.m119was developed into germinated brown rice, whose y-aminobutyric acid content was93.2975mg/100g and much higher than the average level of y-aminobutyric acid in non-glutinous rice, making it have a high nutritional value and good market prospect.