UV-B Stress Regulates the Transcription of UVR8 Signal System-Related Gene and the Synthesis of Isoflavones in Soybean Sprouts

UV-B treatment can promote the accumulation of isoflavones in soybeans. This study investigated the possible medium-wave ultraviolet (UV-B) photoreceptor genes in soybeans and the relationship between the UVR8 signaling system and isoflavones synthesis by designing three germination modes. All predicted GmUVR8 were classified into 10 classes (A-J) based on phylogenetic affinities. Isoflavone biosynthesis genes comprising GmCHS, GmCHR1, GmCHI1A, GmCHI1B, GmCHI4A, GmIFS1, and GmIFS2 were activated in response to UV-B treatment, while the corresponding enzyme activities were stably maintained at high levels. The accumulation of total isoflavones was proportional to the time, regardless of the germination pattern. UV-B treatment promoted the accumulation of isoflavones more than white light treatment and the accumulation of all isoflavones except glycitin was promoted by UV-B. The total isoflavones content of soybean sprouts reached a peak under the irradiation intensity of 45 mu W/cm(2) under different irradiation intensities, which increased by 72.65% compared with that in the dark group. Furthermore, the correlation analysis showed that GmUVR8-E, GmUVR8-F-1, GmUVR8-J(1 similar to 3), GmUVR8-J(4), and GmUVR8-J(5,6) were highly correlated with isoflavones synthesis and might regulate the transcription of isoflavones synthesis gene, presumed as photoreceptor of UV-B in soybean. The results will provide a scientific basis for developing soybean foods rich in isoflavones. [GRAPHICS] .