Saul Ares: COP1 dynamics integrate seasonal light and temperature into a predictive model of Arabidopsis hypocotyl elongation

Plants encounter seasonal combinations of irradiance and temperature with opposing effects on morphology. Focusing on the interplay of PHYTOCHROME B (phyB), EARLY FLOWERING 3 (ELF3), and CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), we present a compact mechanistic model that links upstream signaling to daily hypocotyl growth. Parameters inferred from single- and double-mutant/overexpression series enable the model to reproduce photoperiod responses across temperatures and irradiance levels, and to predict behaviors of genotypes not used for fitting. The analysis shows that COP1’s thermal contribution operates only in daytime, and that the defective response of cop1-4 is epistatic to phyB-9 and elf3-8, establishing COP1 as essential for transducing the thermosensory functions of phyB and ELF3. The framework provides quantitative, testable predictions for environmental and genetic perturbations. As an illustration, we produce global forecasts of daily growth and thermomorphogenic response using astronomical daylength and gridded temperature fields. Finally, we present preliminary incorporation of abscisic acid (ABA) as a light-conditioned attenuation of PIF/SAUR output, consistent with inhibition of hypocotyl elongation in the light and insensitivity in darkness.