The role of HY5-interacting BBX proteins in Arabidopsis

• Applicant: Dr. Henrik Johansson
• Subject Area: Plant Cell and Developmental Biology ; Plant Genetics and Genomics
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 320656366

As the most important environmental signal for plants, light regulates growth and development throughout their life cycle. However, the most dramatic response to light is seen during de-etiolation where light induces a complete switch in development, from skotomorphogenesis to photomorphogenesis. As a key regulator of photomorphogenesis, stabilization and accumulation of the bZIP transcription factor HY5 is essential for de-etiolation. This is achieved by light-dependent inhibition of the E3 ubiquitin ligase COP1/SPA, which targets HY5 for degradation in darkness. Consistently, hy5 mutants show increased hypocotyl elongation and decreased chlorophyll and anthocyanin accumulation when grown in light. Previous work has identified a set of B-box containing proteins that directly interact with COP1 and/or HY5, all belonging to the structural group (IV) of the Arabidopsis B-box zinc finger family. Consistent with their shown interactions with these two major regulators of photomorphogenesis, the B-Box proteins have been described as important regulators of the light signaling pathways. Recently, we provided evidence that three of these proteins (BBX20, BBX21 and BBX22) are absolutely required for HY5 to regulate transcription and photomorphogenic development. Here, we will extend our analysis of the HY5-BBX transcriptional module by 1) performing an extensive phenotypic analysis of the bbx202122 triple mutant, 2) conducting a comparative analysis of BBX20 and BBX21, 3) analyzing the role of the HY5-BBX module during early de-etiolation and 4) identifying novel BBX21 interacting factors.

• DFG Programme: Research Grants