Gamborg s vitamins msp0506

The PBG^{36 (link)}, PBC^{55 (link)}, YHB^{53 (link)} and BCY^{55 (link)} lines of Arabidopsis were previously described. Seeds were surface sterilized^{65 (link)} and plated on half-strength Murashige and Skoog media with Gamborg’s Vitamins (MSP0506, Caisson Laboratories, North Logan, UT), 0.5 mM MES (pH 5.7), and 0.8% (w/v) agar (A038, Caisson Laboratories, North Logan, UT). Seeds were stratified in the dark at 4 °C for 5 days before treatment of specific light and temperature in an LED chamber (Percival Scientific, Perry, IA). For temperature experiments, seedlings were grown first in 21 °C for 2 days (48 h), and then either kept at 21 °C or transferred to 12, 16, or 27 °C for 2 additional days (48 h) before characterization. The light condition was maintained constant at 10 or 50 μmol m⁻² s⁻¹ R light for the entire 4 days. For the shade condition, seedlings were grown in a mixture of 10 μmol m⁻² s⁻¹ R and 10 μmol m⁻² s⁻¹ FR light at 21 °C for 4 days. For dark treatment, BCY and YHB seeds were exposed to 10 μmol m⁻² s⁻¹ FR light for 3 h immediately after stratification to deactivate the remaining phys and induce germination^{65 (link)}, and then kept in the dark at 21 °C for 45 h before a treatment of an indicated temperature for 2 additional days. Fluence rates of light were measured using an Apogee PS200 spectroradiometer (Apogee Instruments Inc., Logan, UT).

All the Arabidopsis (Arabidopsis thaliana) mutants used in this study are in the Col-0 background. Mediator mutants were obtained from the Arabidopsis Biological Resource Center and the detailed list is shown in Supplemental Table S1. Homozygosity was confirmed by polymerase chain reaction (PCR) before the seeds were used for phenotyping. Other Arabidopsis mutants, including pif4-2 (SAIL_1288_E07) and hmr-22, were previously described (Leivar et al., 2008 (link); Qiu et al., 2015 (link), 2019 (link)). Seeds were briefly rinsed with 70% (v/v) ethanol and surface sterilized with bleach (3% sodium hypochlorite, w/v) for 10 min before being plated on half-strength Murashige and Skoog (1/2 MS) media supplemented with Gamborg’s vitamins (MSP0506, Caisson Laboratories, North Logan, UT, USA), 0.5-mM MES (pH 5.7), and 0.8% (w/v) agar (A038, Caisson Laboratories, North Logan, UT, USA). Seeds were stratified in the dark at 4°C for 3–5 days to synchronize germination before treatment under specific light and temperature conditions in LED chambers (Percival Scientific, Perry, IA, USA). Unless otherwise stated, seedlings were grown in continuous R light (50 µmol m⁻² s⁻¹). Fluence rates of light were measured using an Apogee PS200 spectroradiometer (Apogee Instruments Inc., Logan, UT, USA).