title: HFR1 sequesters PIF1 to govern the transcriptional network underlying light-initiated seed germination in Arabidopsis.
abstract: Seed germination is the first step for seed plants to initiate a new life cycle. Light plays a predominant role in promoting seed germination, where the initial phase is mediated by photoreceptor phytochrome B (phyB). Previous studies showed that phytochrome-interacting factor1 (PIF1) represses seed germination downstream of phyB. Here, we identify a positive regulator of phyB-dependent seed germination, long hypocotyl in far-red1 (HFR1). HFR1 blocks PIF1 transcriptional activity by forming a heterodimer with PIF1 that prevents PIF1 from binding to DNA. Our whole-genomic analysis shows that HFR1 and PIF1 oppositely mediate the light-regulated transcriptome in imbibed seeds. Through the HFR1-PIF1 module, light regulates expression of numerous genes involved in cell wall loosening, cell division, and hormone pathways to initiate seed germination. The functionally antagonistic HFR1-PIF1 pair constructs a fail-safe mechanism for fine-tuning seed germination during low-level illumination, ensuring a rapid response to favorable environmental changes. This study identifies the HFR1-PIF1 pair as a central module directing the whole genomic transcriptional network to rapidly initiate light-induced seed germination.
authors.affiliation: Peking-Yale Joint Center for Plant Molecular Genetics and Agro-biotechnology, College of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Shi
authors.forename: Shangwei
authors.initials: S
authors.lastname: Zhong
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Mo
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.forename: Cynthia D
authors.initials: CD
authors.lastname: Nezames
authors.forename: Xing Wang
authors.initials: XW
authors.lastname: Deng
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D053263:Gene Regulatory Networks; D018525:Germination / Q000235:genetics*; D008027:Light; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D051939:Phytochrome B / Q000502:physiology; D055503:Protein Multimerization; D059467:Transcriptome
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051939:Phytochrome B; C414438:At1g02340 protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; C508068:At2g20180 protein, Arabidopsis