The Physicochemical Properties And Gene Expression Analysis Of Starch Synthase In High-amylose Starch Maize

High-amylose maize starch is the important industrial raw material. Its specialphysicochemical properties are the main factors affecting on the qualities of processing andutilization. To provide useful parameter in industry processing of the starch, the content ofamylose, grain plumpness and phenotypic characteristics, phenotypic characteristics of starchgranules, gelatinization and pasting properties, solubility and swelling power of starch weredetermined with thirteen high-amylose maize inbreds and one common inbred (Zheng58).Meanwhile, in order to explore the formation mechanism of different amylose content ofhigh-amylose maize starch, seven kinds of expression of starch synthesis genes in differentperiods after pollination were analyzed with three high-amylose maize inbreds and onecommon inbred (Zheng58). The main results were as follows:1. The results indicated that the amylose content of common inbred was27.72%comparingto that of high-amylose maize inbreds ranged from44.22%to78.81%, which were dividedinto four leves. The highest one reached78.81%.2. The correlation analysis of amylose content and grain plumpness index showed thatamylose content and grain plumpness index was not related(r=0.02681＜0.3).3. Acorrding to the scanning electron micrographs, we found that the A-type starchgranules from the common inbred were full and smooth spheres or polyhedrons with waxyluster but shrunken irregular and dull polyhedrons in high-amylose maize inbreds; There werealso significant changes in B-type starch granules that full and smooth spheres graduallybecame the dull ovals and some were distorted and shapes in the starch with higher amylosecontent.4. The thermal properties (DSC) showed that with the increase of amylose content, To, Tp,Tc and To-Tc gradually increased but△H gradually reduced.5. The pasting properties (RVA) indicated that the common inbred’s starch showed typical"doublets" curve, while high-amylose maize inbred’s starch appeared "S" curves with theincrease of amylose content. Peak viscosity, hot pasting viscosity, final viscosity, breakdown,setback decreased. Peak time increased and pasting temperature did not increase significantly.6. The melting curves and expansion curves showed the same trend in common inbred’s starch and high-amylose maize inbred’s starch: Starch solubility gradually increased with theincrease of temperature from55.0℃to75.0℃,and reached the hightest at75.0℃. Then itgradually decreased to the minimum value at95.0℃. while swelling power increasedcontinuously from55.0℃to95.0℃and the turning point of common inbred’s starch at65.0℃, while at75.0℃in high-amylose maize inbred’s starch.while starch solubility andswelling power decreased significantly with the increase of amylose content.7. Analysis of expression of starch synthesis genes showed that during the period of grainfilling, the expression of the genes(AGPase、GBSSⅠ、SSⅠ、SBEⅠ、SBEⅡb、DBEiso2、DBEiso3) exhibited similar trends.But comparing with the other materials(CK、Ⅴ、Ⅵ),thematerial of Ⅶ showed many differences.