Blue light sensitive photoreceptors of the Zeitlupe (ZTL), Flavin-Kelch-Fbox-1 (FKF1), and LOV-Kelch-Protein-2 (LKP2) family are known to be integral for regulation of circadian rhythm in plants. These proteins have a core LOV (Light, Oxygen, Voltage) domain which is bound to a FMN or FAD cofactor serving as the photo sensory unit. Zeitlupe (ZTL) consist of a single LOV domain bound to FMN which undergoes reversible dark to light state transition characterized by cleavage and formation of a cysteine-FMN adduct respectively. The life-times of such changes vary with the members of the ZTL/FKF1/LKP2 family. Photochemical characterization confirmed that ZTL undergoes adduct decay on a time scale of hours in contrast to FKF1 and LKP2. The fast photo cycle allows detection of the day�night transition facilitating circadian timing. Further characterization suggest that the light induced adduct decay is important for ZTL to serve as a sensor of environmental flux. Here we propose a simple model of primary photochemistry of ZTL and discuss how it serves as an important photoreceptor in circadian rhythm.

Blue light photoreceptor Zeitlupe senses light fluence to regulate plant circadian clock

247th National Meeting (2014)

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