The Effect Of Alteration Of Zein Characters On Agronomic Traits And Digestibility Of Endospermic PB In Maize

Maize seed is important protein resource and widely used in the fields of agriculture, food, medicine and so on. Zein is the main component of storage protein in maize seed, which is playing decisive role in the nutritional quality of maize protein. Zein is composed of 27kD γ,21-27kD α,17-18kD β, 10-14.4kD δ components encoded by the multigene family. They are synthesized on the rough ER and finally accumulated into the ER-derived globular protein body (PB) in the developing endosperm cell. Compared with rice gluten, soy globulin, zein contains high amount of hydrophobic amino acid, sulfur amino acid and low volume of amino acid. Therefore, it is difficult to dissolve and digest and poor balance of amino acids and other nutritional deficiencies. It is necessary to develop varieties of mutant genetic resources of zein. The aim is to carry out the study on breeding of nutritional value on maize protein.The laboratory obtained series of genetic resources of lack of y, specific expression of α0, high molecular weight of β, lack of δ, named as yz-Lack、 aoz-SE、βz-HW、δz-Lack respectively. In order to reveal the influence of variation on agronomic traits of maize and nutritional quality of zein and provide reference for genetic breeding research of maize protein nutritional quality, this study was conducted on the correlation analysis of zein and agronomic traits of maize inbred and the in vitro digestion analysis of PB in the endosperm of zein mutants. The results are as follows:1. The analytical results of agronomic traits and zein traits indicated that: (1) Maize inbred lines had obvious diversity on grain weight single plant, plant height and panicle height. The endosperm traits had greater difference. The ear characters and grain weight single plant had great correlation; (2) βz-HW had significant difference in panicle length, panicle row, row grain number and grain weight single plant. yz-Lack showed significant difference in plant height and panicle height. aoz-SE had significant difference in panicle height and panicle length. δz-Lack showed significant difference in panicle length and panicle row. These results could provide reference for the research on the relationship between agronomic traits and the properties of zein in maize.2. The suitable method was developed to obtain the largest amounts of PB by optimizing the key link of purification for PB in the developing maize endosperm. The obtained PB amount based on the method is about 25 times to the reported method. By optimizing the digestion condition of pepsin, it was established to the most active in vitro digestion condition of 1.0mg/ml pepsin and 50min digestion time. These results could provide technical support for the accurate evaluation of the nutritional quality of zein.3. The digestion analysis of PB in the endosperm of four zeins showed that:compared with the wild type maize inbred lines (PC130), the digestibility for PB of βz-HW was less significantly decreased, the digestibility for PB of yz-Lack was significantly decreased, the digestibility for PB of aoz-SE and δz-Lack was significantly increased. These results suggested that the change of traits on components of zein had varies of degrees of impact on the nutritive value of maize protein. It could arise from the changes of component interaction to PB in the mutant endosperm and the change of accumulation state of PB.The genetic breeding of maize nutritional quality must be in the research on the overall research materials of expression of zein characters of genetic regulation and evaluation of nutritional quality and comprehensive analysis of agronomic traits and yield potential assessment. The results of this study have important theoretical and practical significance on agronomic traits, zein traits and nutritional quality to the target of diversification of breeding on maize protein nutrition quality.