The Characteristics Of Phenotype And The Expression Of Genes Involved In Starch Synthesis In Rice Progenies By Directional Selection

Rice eating and cooking quality are important quality properties and amylose and protein content is important factors which affected the cooking and eating quality. Amylose and protein content is related closely with yield character and the change of amylose and protein content will inevitably lead to the change in other traits.The process of rice grain filling was consistent with the biosynthesis and accumulation of amylose and protein. During grain filling, the activity of key enzymes involved in carbon and nitrogen metabolism and the expression of related gene is related closely with starch quality in grain.Therefore, the selecting of amylose and protein content can increase significantly grain quality and yield traits and genetic diversity in hybrid generation. In addition, the key enzymes and gene involved in carbon and nitrogen metabolism is investigated during the process of selecting of amylose and protein content. The genetic mechanism and molecular biology related to the formation of starch quality. Consequently, selecting amylose and protein content is in theoretical and practical significance in high quality and yield breeding.In our study, two crosses combination, Xixuan 1×Tong 769 and Dongnong 423×Fukei 180, were selected with four parents different in amylose and protein content. In our study, the effect of selecting of amylose and protein content on rice quality, yield, and genetic diversity were investigated in hybrid progenies. Moreover, the regulation of key enzymes and gene expression involved in carbon and nitrogen metabolism was illuminated in rice quality and yield formation. The results were as follows.1. The amylose and protein content were increasd and declined significantly and transgressive progenies were selected through the continuous directional selection of amylose and protein content. The correlation of amylose content, protein content and eating and cooking quality and yield traits changed with the difference of amylose content, protein content.In progenies with high amylose content, the correlation between amylose content and viscosity, decreased viscosity, peak viscosity and setback, taste meter value were not significant. In progenies with low amylose content, the correlation between amylose content and decreased viscosity and setback were significant respectively (-0.811**; 0.913**). In progenies with high protein content, the correlation between protein content and setback and decreased viscosity were significant (0.657*; -0.666*). The correlation between amylose content and peak viscosity, decreased viscosity and setback were significant respectively (-0.669*; -0.835**; 0.922**). In progenies with low protein content, the correlation between protein content and peak viscosity were significant (0.745*). The correlation between amylose content and peak viscosity, decreased viscosity, taste meter value, setback was not significant.In amylose with high amylose content, the correlation between amylose content and grain weight were significant respectively (0.629*), protein content and grain weight were significant respectively (-0.771**). However, in amylose with low amylose content, the correlation between amylose content and protein content and yield traits were not significant.In progenies with high protein content, the correlation between protein content and yield traits were not significant. However, the correlation between protein content and thousand seed weight were significant respectively (-0.812**) in progenies with low protein content.2. The results of SSR molecular marker showed that genetic diversity of 44 hybrid progenies and parents with different amylose and protein were analyzed with 120 SSR primers located on 12 chromosomes in rice. The results indicated that 659 alleles were detected with 108 SSR primers with polymorphism and 6.2 alleles were amplified on average.The results showed that high-polymorphic markers emerged mainly at chromosome 6 and 9 while low-polymorphic markers emerged at chromosome 3 and 7 in progenies with high amylose content. High-polymorphic markers emerged mainly at chromosome 7 and 10 while low-polymorphic emerged at chromosome 1 and 3 in progenies with low protein content. Amylose progeny had more genetic diversity than protein progeny in 2 combinations. CombinationⅡhad more genetic diversity than combinationⅠ.The analyse of genetic diversity in 2 combination showed that the maximum and minimum genetic similarity in combinationⅠwas similar with in combinationⅡ. Cluster analysis of parents and progenies indicated that progenies and parent with high amylose and protein content could cluster together. Progenies with low amylose and protein content could cluster with parents with low amylose and protein content.3. In our study, the changes of ADP-glucose pyrophosphorylase, soluble starch synthesis and starch branching enzyme activities in materials showed a similar tendency. The activities increased to a peak and declined during grain filling with a single-peak curve. The time to reach the peak for 3 enzymes was defferent. There was no difference on the time for ADP-glucose pyrophosphorylase to reach a peak between hybrid progenies. However, there was a significant difference on activities of soluble starch synthesis and starch branching enzyme among hybrid progenies. The time to reach the peak for soluble starch synthesis and starch branching enzyme in low-amylose content progenies was earlier than in high-amylose content progenies.The peak of enzyme activity was different among progenies with different amylose content. The peak of ADP-glucose pyrophosphorylase, soluble starch synthesis and starch branching enzyme activities in high-amylose content progenies were higher significantly than in low-amylose content progenies.During early filling stage, the activities of glutamine synthetase in the progenies with high protein content were higher significantly than in that with low protein content at the early stage of filling and it was opposite at the late stage of grain filling. The activities of proteinase in the progenies with high protein content were higher than in that with low protein content during grain filling.Comparing the peak of key enzymes in carbon and nitrogen metabolism among progenies with different amylose and protein content, transgressive phenomenon were observed. The peak of ADPG pyrophosphorylase, soluble starch synthase, starch branching enzyme activity in the progenies with high amylose content were higher than their parents; The peak of ADPG pyrophosphorylase activity in the progenies with low amylose content were lower than their parents.The peak of glutamine synthetase and proteinase activity in the progenies with high protein content was higher than their parents; the peak of proteinase activity in the progenies with low protein content was lower than their parents.4. The expression of OsAGPase, OsSSSⅠ, OsSBE1 and OsSBE3 the process are manifested. The expression abundance of genes was significantly increased at 17d after heading. The expression abundance of genes was declined at 17d after heading. The change of OsSBE1 and OsSBE3 expression abundance was different. The change of OsSBE1 expression was relatively stable during grain filling, while OsSBE3 expression was decreased rapidly during late filling stage.The relative expression of OsADPase, OsSBE1 and OsSBE3 were not different significantly at 10 days after heading. The relative expression of OsSSSⅠin high amylose lines HS1 and HS2 was significantly lower than the low amylose content selection and future generations lines LS1, LS2, and also lower than the gene expression of their parents.