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Arabidopsis Transcription Factor ELONGATED HYPOCOTYL5 Plays a Role in the Feedback Regulation of Phytochrome A Signaling

Li, Jigang, Li, Gang, Gao, Shumin, Martinez, Cristina, He, Guangming, Zhou, Zhenzhen, Huang, Xi, Lee, Jae-Hoon, Zhang, Huiyong, Shen, Yunping, Wang, Haiyang, Deng, Xing Wang
The plant cell 2010 v.22 no.11 pp. 3634-3649
Arabidopsis thaliana, DNA-binding domains, binding sites, far-red light, photoreceptors, phytochrome, transcription factors
Phytochrome A (phyA) is the primary photoreceptor responsible for perceiving and mediating various responses to far-red light in Arabidopsis thaliana. FAR-RED ELONGATED HYPOCOTYL1 (FHY1) and its homolog FHY1-LIKE (FHL) are two small plant-specific proteins essential for light-regulated phyA nuclear accumulation and subsequent phyA signaling processes. FHY3 and its homolog FAR-RED IMPAIRED RESPONSE1 (FAR1) are two transposase-derived transcription factors that directly activate FHY1/FHL transcription and thus mediate subsequent phyA nuclear accumulation and responses. Here, we report that ELONGATED HYPOCOTYL5 (HY5), a well-characterized bZIP transcription factor involved in promoting photomorphogenesis, directly binds ACGT-containing elements a few base pairs away from the FHY3/FAR1 binding sites in the FHY1/FHL promoters. We demonstrate that HY5 physically interacts with FHY3/FAR1 through their respective DNA binding domains and negatively regulates FHY3/FAR1-activated FHY1/FHL expression under far-red light. Together, our data show that HY5 plays a role in negative feedback regulation of phyA signaling by attenuating FHY3/FAR1-activated FHY1/FHL expression, providing a mechanism for fine-tuning phyA signaling homeostasis.