Combined analysis of transcriptome and metabolite data reveals extensive differences between black and brown nearly-isogenic soybean (Glycine max) seed coats enabling the identification of pigment isogenes

Metabolite composition and gene expression differences between black (iRT) and brown (irT) seed coats are far more extensive than previously thought. Putative anthocyanin, proanthocyanidin, (iso)flavonoid, and phenylpropanoid isogenes were differentially-expressed between black (iRT) and brown (irT) seed coats, and UGT78K2 and OMT5 were validated to code UDP-glycose:flavonoid-3-O-glycosyltransferase and anthocyanin 3'-O-methyltransferase proteins in vitro, respectively. Duplicate gene copies for several enzymes were overexpressed in the black (iRT) seed coat suggesting more than one isogene may have to be silenced to engineer seed coat color using RNA interference.