Types Of AGP Isozyme And The Relationship Between Isozymes And Starch Content In Common Wheat

ADP-Glucose pyrophosphorylase(AGP) is a key enzyme in starch synthesis. It controls a rate-limiting step in the starch biosynthesis in developing wheat seeds and, therefore, should be a prominent determinant of seed sink strength. Evidence is presented for the existence of AGP isozymes in common wheat (Triticum aestivum L.) endosperm. Following an approach already shown to be successful in maize (zea mays L.), native polyarcylamide gel electrophoresis (native PAGE) was designed to identify AGP isozyme patterns from crude enzyme preparations. The primary researches on AGP in wheat were focus on the dynamic changes and the affection to the starch content of the enzyme by these years. But there was little report to show that how many isozymes of AGP in wheat .To explore the number of AGP and the relationship between isozyme genotypes and total content of starch in wheat grains, activity of AGP and content of starch ware measured in 60 cultivars from 17 provinces in China. The main results are as follows:1. The dynamic changes of AGP in the growth of wheat seed.The dynamic changes of AGP of 6 cultivars has been measured. The result shows that the activity of AGP appeared as a single-peak curve, and the peak emerged at 20 days after flower. At the beginning, the activity of AGP was very low, and holding this level for a short time until 5 days after flower. The activity came down after 20 days after flower. But even when the growth of seed was over, AGP still hold some activity.2. All the isozymes of AGP in wheat. There is no report show us how many kinds of AGP isozyme are exist in wheat, and that's what we have done in this paper. In this work, we made the Native-PAGE which has been used in maize become easier and more available to check up the isozymes in wheat. The result shows that there are several kinds of AGP isozyme, and they appeared in different space and time in wheat.3. To explore the relationship between isozyme genotypes and total content of starch in wheat grains, activity of AGP and content of starch ware measured in 60 cultivars from 17 provinces in China. The genotypes of AGP isozyme were also identified by native PAGE. In this paper, we show that there were four alleles, AGPa, AGPb, AGPc and AGPd, with frequencies of 96.7%, 80%, 86.7%, and 16.7% respectively. Five genotypes were determined in which AGPabc took on the highest frequency of 46.7% and AGPbc took on the lowest frequency of 3.3%. The activity of AGP and total content of starch in the cultivars with distinct genotypes were significantly different (P<0.05). The cultivars with genotype AGPabcd and AGPabc showed a high value of AGP activity and total content of starch. The lack of AGPa, AGPb or AGPc in cultivars resulted in a low value of AGP activity and total content of starch. It indicated that different genotypes of AGP isozyme show distinct genetic impacts on enzyme activity and content of starch in common wheat.