title: Phytochrome-interacting factor 4 (PIF4) regulates auxin biosynthesis at high temperature.
abstract: At high ambient temperature, plants display dramatic stem elongation in an adaptive response to heat. This response is mediated by elevated levels of the phytohormone auxin and requires auxin biosynthesis, signaling, and transport pathways. The mechanisms by which higher temperature results in greater auxin accumulation are unknown, however. A basic helix-loop-helix transcription factor, PHYTOCHROME-INTERACTING FACTOR 4 (PIF4), is also required for hypocotyl elongation in response to high temperature. PIF4 also acts redundantly with its homolog, PIF5, to regulate diurnal growth rhythms and elongation responses to the threat of vegetative shade. PIF4 activity is reportedly limited in part by binding to both the basic helix-loop-helix protein LONG HYPOCOTYL IN FAR RED 1 and the DELLA family of growth-repressing proteins. Despite the importance of PIF4 in integrating multiple environmental signals, the mechanisms by which PIF4 controls growth are unknown. Here we demonstrate that PIF4 regulates levels of auxin and the expression of key auxin biosynthesis genes at high temperature. We also identify a family of SMALL AUXIN UP RNA (SAUR) genes that are expressed at high temperature in a PIF4-dependent manner and promote elongation growth. Taken together, our results demonstrate direct molecular links among PIF4, auxin, and elongation growth at high temperature.
authors: School of Biological Sciences, University of Bristol, Bristol BS8 1UG, United Kingdom. kerry.franklin@bristol.ac.uk
authors: Keara A
authors: KA
authors: Franklin
authors: Sang Ho
authors: SH
authors: Lee
authors: Dhaval
authors: D
authors: Patel
authors: S Vinod
authors: SV
authors: Kumar
authors: Angela K
authors: AK
authors: Spartz
authors: Chen
authors: C
authors: Gu
authors: Songqing
authors: S
authors: Ye
authors: Peng
authors: P
authors: Yu
authors: Gordon
authors: G
authors: Breen
authors: Jerry D
authors: JD
authors: Cohen
authors: Philip A
authors: PA
authors: Wigge
authors: William M
authors: WM
authors: Gray
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D006358:Hot Temperature; D007210:Indoleacetic Acids / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D007210:Indoleacetic Acids; C459466:PIF4 protein, Arabidopsis