**42. Isoflavone synthase**

Isoflavonoids are secondary metabolites important in nodulation and defense responses. They have a common occurrence in leguminous plants. Isoflavone synthase (IFS) catalyzes the key entry point step of isoflavone biosynthesis from the general phenylpropanoid path‐ way. IFS transcripts were detected in seeds and roots. The transcript levels of the isoforms IFS1 and IFS2 are altered in response to *Bradyrhizobium japonicum* or salicylic acid. The ex‐ pression pattern of IFS1 in soybean is indicative of the roles of isoflavonoids in defense against pathogens and signal molecules to symbiotic bacteria [46].
