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Isolation and characterization of soybean chalcone reductase cDNA, which encodes the key enzyme for the biosynthesis of 4,2′,4′-trihydroxychalcone in legumes

Zhang, Zhuo, Fu, Yongping, Ma, Jian, Zhang, Chao, Wang, Piwu
Molecular breeding 2014 v.34 no.4 pp. 2139-2149
Glycine max, Phytophthora sojae, bacteria, biosynthesis, catalytic activity, chalcone reductase, chromosomes, complementary DNA, cultivars, daidzein, disease resistance, fluorescence, genes, high performance liquid chromatography, naringenin-chalcone synthase, open reading frames, pathogens, phytoalexins, quantitative polymerase chain reaction, roots, soybeans, tobacco
In plants, phytoalexins induced by pathogen attack play an important role in disease resistance. In soybean [Glycine max L. (Merr.)], attack by pathogenic bacteria induces the synthesis of isoflavonoids, especially daidzein. Chalcone reductase (CHR) is the key enzyme in the biosynthesis of daidzein. Along with chalcone synthase, it catalyzes the formation of isoliquiritigenin, which is a necessary substrate for daidzein biosynthesis. In this study, a CHR gene, Gmchr2 (GenBank code: KF758395), was isolated from the soybean cultivar Jinong 17. The cDNA consisted of a 1,417-bp fragment that included an open reading frame of 969 bp. The gene is located on chromosome 9 of the soybean genome. Phytophthora sojae was inoculated onto soybean roots, and changes in the transcript levels of the chr genes and the catalytic activity of CHR were investigated in different soybean tissues by real-time fluorescence quantitative PCR and high-performance liquid chromatography (HPLC), respectively. The results showed that the isoliquiritigenin content in roots significantly increased after pathogen inoculation. The Gmchr2 gene was transformed into tobacco, and the presence of isoliquiritigenin in the transformants was confirmed by HPLC. Expression of the Gmchr2 gene under the control of the 35S CaMV promoter was also confirmed. This characterization of a chr gene encoding a soybean CHR helps to shed light on the biological synthesis and regulation of soybean isoflavones and will be useful for manipulating the phenylpropanoid pathway leading to isoflavonoid phytoalexins.