title: PIF1 directly and indirectly regulates chlorophyll biosynthesis to optimize the greening process in Arabidopsis.
abstract: Plants depend on light signals to modulate many aspects of their development and optimize their photosynthetic capacity. Phytochromes (phys), a family of photoreceptors, initiate a signal transduction pathway that alters expression of a large number of genes to induce these responses. Recently, phyA and phyB were shown to bind members of a basic helix-loop-helix family of transcription factors called phy-interacting factors (PIFs). PIF1 negatively regulates chlorophyll biosynthesis and seed germination in the dark, and light-induced degradation of PIF1 relieves this negative regulation to promote photomorphogenesis. Here, we report that PIF1 regulates expression of a discrete set of genes in the dark, including protochlorophyllide oxidoreductase (POR), ferrochelatase (FeChII), and heme oxygenase (HO3), which are involved in controlling the chlorophyll biosynthetic pathway. Using ChIP and DNA gel-shift assays, we demonstrate that PIF1 directly binds to a G-box (CACGTG) DNA sequence element present in the PORC promoter. Moreover, in transient assays, PIF1 activates transcription of PORC in a G-box-dependent manner. These data strongly suggest that PIF1 directly and indirectly regulates key genes involved in chlorophyll biosynthesis to optimize the greening process in Arabidopsis.
authors.affiliation: Section of Molecular Cell and Developmental Biology and The Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Moon
authors.forename: Ling
authors.initials: L
authors.lastname: Zhu
authors.forename: Hui
authors.initials: H
authors.lastname: Shen
authors.forename: Enamul
authors.initials: E
authors.lastname: Huq
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D002734:Chlorophyll / Q000096:biosynthesis*; D005294:Ferrochelatase / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006418:Heme / Q000096:biosynthesis; D009154:Mutation / Q000235:genetics; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011521:Protochlorophyllide / Q000378:metabolism; D036226:Seedlings / Q000378:metabolism; D045725:Tetrapyrroles / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D002734:Chlorophyll; D005294:Ferrochelatase; D006418:Heme; D044925:Oxidoreductases Acting on CH-CH Group Donors; D011521:Protochlorophyllide; D045725:Tetrapyrroles; C508068:At2g20180 protein, Arabidopsis; C023886:protochlorophyllide reductase