Two novel repressors of photomorphogenesis act downstream of HY5 in Arabidopsis (Plant Physiol)

Higher plants rely on a sophisticated photo-sensory system to cope with the vast variety of environmental stimuli. Under light conditions, young seedlings display photomorphogenic development to maxize the usage of light. Recently, YQ Heng et al. discovered two B-box containing proteins, BBX30 and BBX31, can repress photomorphogenesis in Arabidopsis. The central positive regulator ELONGATED HYPOCOTYL 5 (HY5) directly binds the G-box present in their promoters to prevent their transcription. Since HY5 is well-known for controlling numerous positive regulator of light signaling to boost photomorphogenesis, this study shows that HY5 is also capable of inhibiting the function of negative regulators of light signaling, suggesting higher plants coordinate an antagonistic regulatory machinery that controls plant photomorphogenesis. (Summarized by Nanxun Qin) Plant Physiol. 10.1104/pp.18.01244