| People pay more and more attention to soybean isoflavones as it is a class of biological active substances and have health care function to human. The content of isoflavones is affected by environmental conditions and genotypes. Geting higer isoflavones content varieties with traditional breeding or gene engineering method will provide the ideal raw material for soybean isoflavones production and processing, which is also the most effective way to benefit more persons. To deeply understand the metabolic difference among different soybean varieties with different isoflavone content, we chose the six soybean varieties with different isoflavones content and similar number of growing days to analyse it. Considering the effect of environment condition to the isoflavones content of soybean seeds, we planted the 6 varieties in two times(the first batch varities planted in April 30 th, the second batch varities planted in May 15th). All the samples was processed and measured at the same time after the last time sampling. The content of isoflavones have been measured in the seeds growth stages(R5-R8). The content of free phenylalanine, coumaric acid and naringenin(R5-R7) have been measured. The expression of key enzyme genes in the isoflavones biosynthetic metabolic pathway(R5-R7) have been measured. The results are as follows.(1) The result of variance for sowing date and varieties show: Sowing date and varieties have significant or extremely significant effect to the contents of daidzein, glycitein, genistein and isoflavones in soybean seeds(R8). The average of the content of isoflavones in soybean seeds of the first batch is 993.35ug/g, the average of the content of isoflavones in soybean seeds of the second batch is 1039.35ug/g, the content of soybean isoflavones in the second sowing batch is higher than the first sowing batch significantly. The concent of isoflavones has a significant difference among varieties, and the range of different content of isoflavones among varieties is greater than the difference during the sowing date. The content of isoflavones of L12 is highest in varities(1476.57ug/g), the content of isoflavones of L11 is lowest in varities(534.19ug/g), the content of L12 is 2.76 times than L11.(2) The content of free phenylalanine was gradually reduced in seeds, and the cotent of all varieties are highest in R5 period in three growth stages, then the cotent gradually reduced in the period R6 and R7. The content of coumaric acid is soybean seeds gradually increased from R5 to R7. The content of naringenin gradually reduced from R5 to R7, and, the coumaric acid content of the five varieties from the six varieties nearly cannot be checked out except L6 in R7 stage. From this part study, we did not find the evidence that anyone in our choosing three kind of substrate can determined the content of isoflavones among the six soybean varieties. So, we think that perhaps the speed of flow of substrate not the content of substrate determine the content of isoflavones in soybean seeds.(3) Real-time PCR technology has been applied to appraise the expression of key enzyme genes in isoflavones biosynthetic pathway in the different growth stages(R5-R7) of soybean seeds. Through the hierarchical clustering and heat map analysis, we found that PAL2, CHS8, HID, CHI1 A and IFS1 genes gathered to the first class, and the others gathered to the second class. The first class of genes has a higher order of magnitude of the expression than the second class of genes. The expression of the first class of genes increased with the content of isoflavones increasing during soybean seeds developing. The expression of the second class of genes did not shown the similar phenomenon with soybean isoflavones accumulation in different growth stages of soybean seeds. Through the further analysis, we found that the expression of phenylalanine ammonialyase(PAL2) gene in the soybean varities with high content of isoflavones were higher than it in the soybean varities with low content of isoflavones. |
PDF Full Text Request