Soybean (Glycine max) PHYTOCHROME-INTERACTION FACTOR 1 induced skotomorphogenesis and de-etiolation in Arabidopsis

Skotomorphogenesis occurs after germination and before excavation in plants. It inhibits excessive absorbed energy in cells and can prevent the lethal photooxidative damage caused by transitioning from skotomorphogenesis to photomorphogenesis for light energy utilization. To investigate the mechanisms underlying photoreactions in soybean [Glycine max (L.) Merr.], we identified and isolated soybean phytochrome-interaction factor 1 (GmPIF1). A yeast two-hybrid (Y2H) assay showed that GmPIF1 interacted with photoactive PHYTOCHROME A (PHYA) and B (PHYB) in both soybean and Arabidopsis (GmPHYA, GmPHYB, AtPHYA, and AtPHYB). To analyze its function, we ectopically over-expressed GmPIF1 in wild type and pif1 mutant Arabidopsis. In etiolated seedlings, GmPIF1 caused hypocotyl elongation, cotyledon closed, apical hooks folded, and less accumulation of protochlorophyllide. In Y2H, GmPIF1 interacted with AtHDA15 that inhibited chlorophyll synthesis under dark conditions. After transition from darkness to white light, GmPIF1 promotes the reduction of photobleaching and induced de-etiolation. Moreover, GmPIF1 inhibited PHYA- and PHYB-mediated seed germination. Our findings increase our understanding of the regulatory network of light response in soybean and provide useful gene resources for soybean breeding in programs and genetics engineering.