The rye photoreceptor ScphyB integrates light signals to control development and architecture in Arabidopsis thaliana.

As an important food and feed crop, cultivated rye (Secale cereale L.) exhibits excellent resistance to biotic and abiotic stresses, making it a valuable genetic resource for wheat improvement. However, the functions of phytochromes in rye remain poorly characterized. Here, we cloned and characterized PhyB from the Weining rye variety (ScPhyB). The predicted protein contains conserved phytochrome domains-PAS, GAF, PHY, and HATPase-and phylogenetic analysis revealed that ScPhyB is most closely related to wheat TaPhyB, with both belonging to the monocot clade. Promoter analysis identified multiple cis-acting elements related to hormone response, meristem expression, low temperature responsiveness, light response, and MYB binding. Heterologous expression of ScPhyB in Arabidopsis enhanced photomorphogenesis under white light (WL), red light (R), and blue light (B). Furthermore, ScPhyB attenuated shade avoidance responses to 70 % and 90 % of wildtype seedlings measured by hypocotyl length by perceiving high and low R/FR red to far-red (R/FR) light ratio, respectively. ScPhyB also modulated plant architecture and delayed flowering (6-7d) by repressing FT expression. Yeast two-hybrid (Y2H) assays and split-luciferase (LUC) assay confirmed that ScPhyB interacts with both ScPIF3 and ScCOP1, indicating functional conservation within the PIF signaling pathway and the COP1-SPA1 complex. Our findings provide insight into the role of ScPhyB in light signaling and suggest its potential utility for improving crop traits.