Abstract: In this present study, two soybean cultivars with different drought tolerance in serial number of JP-6 (high drought-tolerant species) and JP-16 (low drought-tolerant species) were researched. The HPLC and real-time PCR analyses were used to determine the isoflavone contents and relative expression levels of key genes, which encoded isoflavone synthesis relative enzymes in lea-ves and roots under different drought stress levels, respectively. The results indicated that the isoflavone contents in roots were significantly higher than that in leaves, whereas the relative expression of isoflavone synthetic enzyme related genes in leaves was significantly higher than that in roots. Analysis of isoflavone accumulation by comparing two different drought tolerance soybean cultivars found that the isoflavone accumulation in roots of JP-6 was greater than that in others. With increa-sing levels of the drought stress, there were significant differences in both isoflavone synthesis and accumulation between JP-6 and JP-16 soybean cultivars. In JP-6, the isoflavone accumulation in root and leaf increased after slight decreasing, while the opposite result was obtained in JP-16, in which the isoflavone accumulation in different parts were decreased after slight increasing. The expression of isoflavone synthesis relative enzyme genes presented a trend that decreased and then gradually increased with the increasing level of drought stress, except C4H, 4CL and IFS2 which were synthesis genes upstream of isoflavones in leaves of JP-6. Soybean isoflavones were mainly synthesized in leaves, little was synthesized in roots. The isoflavone synthesis and accumulation of low drought-tolerant species were scare, while those of high drought-resistant variety were relatively higher. The variety with high isoflavone accumulation in the root was more drought-resistant.

Key words: drought stress, transfer, isoflavone, synthesis, soybean