Light-mediated seedling development of hy1 atmyc2. A, Phenotype of wild-type and various mutant seedlings in different light conditions. Six-day-old constant WL (90 μmol m-2 s-1), RL (90 μmol m-2 s-1), FR (90 μmol m-2 s-1) and BL (45 μmol m-2 s-1) grown seedlings. B-E, Quantification of hypocotyl length of 6-day-old constant WL (90 μmol m-2 s-1), RL (90 μmol m-2 s-1), FR (90 μmol m-2 s-1) and BL (45 μmol m-2 s-1) grown seedlings, respectively. F-G, The relative expression of CAB1 and RBCS-1A in 6-day-old seedlings grown in WL (90 μmol m-2 s-1). The error bars indicate SD. Approximately 25 to 30 seedlings were used for hypocotyl length measurement. For gene expression studies, total RNA was isolated from 100 mg of tissue was used for cDNA preparation. The real-time PCR experiments were repeated more than twice and three technical replicates were used for each genotype. Similar results were obtained in all the experiments. A representative graph is shown. H, Working model shows the role of HY1, HY5 and MYC2 in photomorphogenesis and JA responsiveness. HY1 and HY5 act additively in response to JA and light signaling pathways. MYC2 acts downstream to HY1 in JA responsiveness, and HY1 acts negatively to MYC2-mediated BL specific photomorphogenic growth.