title: PIF4 and PIF5 transcription factors link blue light and auxin to regulate the phototropic response in Arabidopsis.
abstract: Both blue light (BL) and auxin are essential for phototropism in Arabidopsis thaliana. However, the mechanisms by which light is molecularly linked to auxin during phototropism remain elusive. Here, we report that phytochrome interacting factoR4 (PIF4) and PIF5 act downstream of the BL sensor phototropin1 (PHOT1) to negatively modulate phototropism in Arabidopsis. We also reveal that PIF4 and PIF5 negatively regulate auxin signaling. Furthermore, we demonstrate that PIF4 directly activates the expression of the auxin/indole-3-acetic acid (IAA) genes IAA19 and IAA29 by binding to the G-box (CACGTG) motifs in their promoters. Our genetic assays demonstrate that IAA19 and IAA29, which physically interact with auxin response factor7 (ARF7), are sufficient for PIF4 to negatively regulate auxin signaling and phototropism. This study identifies a key step of phototropic signaling in Arabidopsis by showing that PIF4 and PIF5 link light and auxin.
authors.affiliation: State Key Laboratory of Plant Genomics, National Centre for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Jiaqiang
authors.initials: J
authors.lastname: Sun
authors.forename: Linlin
authors.initials: L
authors.lastname: Qi
authors.forename: Yanan
authors.initials: Y
authors.lastname: Li
authors.forename: Qingzhe
authors.initials: Q
authors.lastname: Zhai
authors.forename: Chuanyou
authors.initials: C
authors.lastname: Li
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D018546:Hypocotyl / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D015151:Immunoblotting; D007210:Indoleacetic Acids / Q000494:pharmacology*; D008027:Light; D009154:Mutation; D018524:Phototropism / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D010937:Plant Growth Regulators / Q000494:pharmacology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D014157:Transcription Factors; C503425:ARF7 protein, Arabidopsis; C483308:IAA19 protein, Arabidopsis; C586769:IAA29 protein, Arabidopsis; C459466:PIF4 protein, Arabidopsis; C497729:PIF5 protein, Arabidopsis