Fig. 6.

The C-terminal SPA1-interaction domain of phyB is essential for photobody formation and PIF1 phosphorylation. a Immunoblots showing the level of native PIF1 in two independent transgenic lines of phyB-GFP FL (#31 and #24) and phyB-GFP ΔC (#44 and #27) along with wild type and phyAB as controls. Total protein was extracted from 4-day-old dark-grown seedlings either kept in darkness or exposed to continuous red light (3.5 μmolm⁻² s⁻¹) over time. b A graph showing the amount of PIF1 levels in response to red light exposure over time. c, d The light-induced phosphorylation of PIF1 is defective in phyB-GFP ΔC compared to phyB-GFP FL. e The phyB-SPA1 interaction is necessary for phyB nuclear transport and photobody formation. The phyB-GFP FL produces nuclear photobodies after 5 h of red light (10 µmolm⁻² s⁻¹) treatment (left), whereas phyB-GFP ΔC showed dispersed nuclear signals (right). Bar = 15 μm. f The cytoplasmic GFP signals were quantified from phyB-GFP FL and phyB-GFP ΔC images by imageJ (n = 12), Error bar = SD. ***p-value < 0.00001, student’s t-test