Comparison Analysis Of Expression Characteristics And Promoter Sequence Structures Of Starch Branching Enzyme Gene In Rice

The composition and structure of starch is the most important factor to determine the quality of rice.Starch branching enzyme(SBE)is one of the key regulatory enzymes in the process of rice starch synthesis,and has three kinds of isozymes,Os SBEI,Os SBEIIb and Os SBEIIa.Gene promoter determines the time,location and intensity of gene expression.Research on the gene promoter structure can explain the gene expression characteristics to a certain extent.In this study,progenies and parents which have transgressive variation in the amylose content,Indica rice Bashier,glutinous rice Longdao 8 as tested material.Analysis of starch component content,SBE activity,SBE isoform gene expression during different filling period through pot incubation tese and cloning the SBE isoform gene promoter of six materials.Analysis of the base mutations and regulatory elements changes in promoter sequences.The aim of this study was to clarify the regulation mechanism of amylose accumulation,the relationship between promoter structure variation and transcriptional expression,to provide theoretical basis for the molecular means of quality improvement.The results are as follows:The amylose,amylopectin and total starch contents of six tested materials showed a linear growth during grain filling process,amylose content accumulated amount and speed of Indica Rice was higher than that of Japonica Rice than Glutinous Rice;The lower amylose content was,the higher peak viscosity,hot paste viscosity and breakdown value was,decreased the amylose content could improve rice cooking and eating quality.The SBE activity during grain filling process showed a single peak curve,reached the peak at20 d after heading around then decline,the SBE activity of high amylose content varieties was higher than low amylose content varieties,Indica Rice > Japonica Rice > Glutinous Rice.During the filling process,the dynamic change of the transcriptional expression of SBE isoform gene was consistent with the change of enzyme activity,and the two had a significant positive correlation.The gene expression of Os SBEIIb gene in endosperm was the highest,followed by Os SBEI,and the expression of Os SBEIIa gene was the lowest,almost no expression.Among the SBE isoform gene of six tested materials,variability of Os SBEIIb promoter sequence was the lowest,and compared with Nipponbare,the homology up to 99.93%,the promoter of Os SBEI gene was 99.20%,the Os SBEIIa gene promoter was 96.90%,variability of Os SBEIIa promoter sequence was the highest.Although the SBE isoforms gene promoters had different degree of base variation,these mutations did not cause changes in types of the promoter regulatory element,only caused changes in quantities.The promoter sequences of SBE isoform gene contained many cis-acting elements,which not only contain the basic core regulatory elements,strengthen regulatory elements,seed-specific expression essential elements,but also contain a large amount of light responsive elements,hormone responsive elements,stress-inducible responsive elements,tissue expression responsive elements.Progenies and parents which have transgressive variation had different degree of variation in SBE isoform gene promoter sequences,Os SBEI had only one base variation which caused by two kinds of regulatory elements changed;Os SBEIIb sequence had four variations caused by four kinds of regulatory elements change;five base variations of Os SBEIIa lead to the seven regulatory elements change.