Light- and Phytochrome-Dependent Regulation of Hypocotyl Elongation in Arabidopsis thaliana

To identify and characterize genes required for tissue-specific phytochrome responses during hypocotyl development in far-red-light grown bvr lines, we performed gene transcriptional profiling using bvr lines with mesophyll-specific phytochrome inactivation (cab3: :pBVR2). We identified several candidate genes whose expression is significantly altered in lines with mesophyll tissue-specific BVR expression (Cab3::pBVR2), compared to constitutive phytochrome inactivation lines, i.e. 35S-driven BVR lines (35S::pBVR3). No-0 is used as wild-type (WT) Seeds of No-0 WT, 35S::pBVR3 and CAB3::pBVR2 on MS plates were exposed to Red (R) light of 75 µmol m-2 s-1 for 5 min and imbibing seeds were cold-stratified at 4 °C in darkness for 3 d. Seedlings were grown under continuous far-red illumination for 7 d. Seven-day-old vegetative whole seedlings (300 – 500 mg) were quickly (<1 min) harvested and immediately frozen in liquid nitrogen inside the FR chamber. Seedlings were grown under continuous far-red illumination for 7 d.