Phytophthora root and stem rot of soybean (Glycine max (L.) Merr.) caused by Phytophthora sojae is a destructive disease worldwide.

The enzyme 4-coumarate: CoA ligase (4CL) has been extensively studied with regard to plant responses to pathogens. However, the molecular mechanism of the response of soybean 4CLto P. sojae remains unclear. In a previous study, a highly upregulated 4CL homologue was characterised through suppressive subtractive hybridisation library and cDNA microarrays, in the resistant soybean cultivar ‘Suinong 10’ after infection with P. sojae race 1. Here, we isolated the full-length EST, and designated as GmPI4L (P. sojae-inducible 4CL gene) in this study, which is a novel member of the soybean 4CL gene family. GmPI4L has 34–43% over all amino acid sequence identity with other plant 4CLs. Overexpression of GmPI4Lenhances resistance to P. sojae in transgenic soybean plants. The GmPI4L is located in the cell membrane when transiently expressed in Arabidopsis protoplasts. Further analyses showed that the contents of daidzein, genistein, and the relative content of glyceollins are significantly increased in overexpression GmPI4Lsoybeans. Taken together, these results suggested that GmPI4L plays an important role in response to P. sojae infection, possibly by enhancing the content of glyceollins, daidzein, and genistein in soybean.