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  • Mechanism of early light signaling by the carboxy-terminal output module of Arabidopsis phytochrome B.

Mechanism of early light signaling by the carboxy-terminal output module of Arabidopsis phytochrome B.

Nature communications (2017-12-05)
Yongjian Qiu, Elise K Pasoreck, Amit K Reddy, Akira Nagatani, Wenxiu Ma, Joanne Chory, Meng Chen
ABSTRACT

Plant phytochromes are thought to transduce light signals by mediating the degradation of phytochrome-interacting transcription factors (PIFs) through the N-terminal photosensory module, while the C-terminal module, including a histidine kinase-related domain (HKRD), does not participate in signaling. Here we show that the C-terminal module of Arabidopsis phytochrome B (PHYB) is sufficient to mediate the degradation of PIF3 specifically and to activate photosynthetic genes in the dark. The HKRD is a dimerization domain for PHYB homo and heterodimerization. A D1040V mutation, which disrupts the dimerization of HKRD and the interaction between C-terminal module and PIF3, abrogates PHYB nuclear accumulation, photobody biogenesis, and PIF3 degradation. By contrast, disrupting the interaction between PIF3 and PHYB's N-terminal module has little effect on PIF3 degradation. Together, this study demonstrates that the dimeric form of the C-terminal module plays important signaling roles by targeting PHYB to subnuclear photobodies and interacting with PIF3 to trigger its degradation.

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Sigma-Aldrich
Z-Leu-Leu-Norvalinal, ≥90% (HPLC), powder