GmPHD6 interacts with LHP1-1 or LHP1-2 and the LHP1s have transcriptional activation activity. A, GmPHD6 interacts with LHP1-1 and LHP1-2 in a yeast two-hybrid assay. Yeast strains were grown on QDO/X/A or YPDA plates for 3 d. Blue colonies indicate positive interactions. B, Domain analysis of LHP1-1 and LHP1-2. C, Western-blotting result of GST pull-down assay. The MBP-LHP1 fusion protein was pulled down by GST-GmPHD6 but not by GST-GmPHD5 or GST. The arrows pointed to the expressed GST or its fusion proteins. D, Western-blotting result of the Co-IP assay. The Flag-GmPHD6 protein was coimmunoprecipitated with the LHP1-MYC protein using antic-Myc agarose beads. E, Transcriptional regulation activity of BD-GmPHD6 and/or BD-LHP1 determined by a DLR assay using an Arabidopsis protoplast. Relative LUC Activity = (Firefly LUC activity) / (Renilla LUC activity). For the plasmid ratio, pTRL:Reporter (LUC):Effector = 1:6:6 (µg/µg/µg). Bars indicate sd (n = 3). Asterisks indicate significant difference (**P < 0.05) compared to negative control (BD). F, The transcriptional regulation activity of the GmPHD6/LHP1 complex is shown. For the plasmid ratio, pTRL:LUC:BD-GmPHD6:35s-LHP1 = 1:6:6:6 (µg/µg/µg/µg). Bars indicate SD (n = 3). Asterisks indicate significant difference (*P < 0.05 and **P < 0.01) compared to BD+LHP1. CHROMO, chromatin organization modifier domain.