AUTHOR=Li Jia , Li Changfu , Gou Junbo , Wang Xin , Fan Rongyan , Zhang Yansheng 

TITLE=An Alternative Pathway for Formononetin Biosynthesis in Pueraria lobata

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00861

DOI=10.3389/fpls.2016.00861

ISSN=1664-462X

ABSTRACT=<p>The <italic>O</italic>-methylation is an important tailing process in <italic>Pueraria lobata</italic> isoflavone metabolism, but the molecular mechanism governing it remains not elucidated. This manuscript describes the mining of key <italic>O</italic>-methyltransferases (OMTs) involved in the process. Using our previously constructed <italic>P. lobata</italic> transcriptome, the OMT candidates were searched, extensively analyzed, and their functions were investigated by expression in yeast, <italic>Escherichia coli</italic>, or <italic>Glycine max</italic> hairy roots. Here, we report the identification of the key OMT gene responsible for formononetin production in <italic>P. lobata</italic> (designated as <italic>PlOMT9</italic>). PlOMT9 primarily functions as an isoflavone-specific 4′-<italic>O</italic>-methyltransferase, although it shows high sequence identities with isoflavone 7-<italic>O</italic>-methyltransferases. Moreover, unlike the previously reported OMTs that catalyze the 4′-<italic>O</italic>-methylation for formononetin biosynthesis at the isoflavanone stage, PlOMT9 performs this modifying step at the isoflavone level, using daidzein rather than 2,7,4′-trihydroxy-isoflavanone as the substrate. Gene expression analyses and metabolite profiling supported its proposed roles in <italic>P. lobata</italic>. Using the system of transgenic <italic>G. max</italic> hairy roots, the role of PlOMT9 in the biosynthesis of formononetin was further demonstrated <italic>in vivo</italic>.</p>