The Arabidopsis NRT1/PTR FAMILY protein NPF7.3/NRT1.5 is an indole-3-butyric acid transporter involved in root gravitropism

Proc Natl Acad Sci U S A. 2020 Dec 8;117(49):31500-31509. doi: 10.1073/pnas.2013305117. Epub 2020 Nov 20.


Active membrane transport of plant hormones and their related compounds is an essential process that determines the distribution of the compounds within plant tissues and, hence, regulates various physiological events. Here, we report that the Arabidopsis NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER FAMILY 7.3 (NPF7.3) protein functions as a transporter of indole-3-butyric acid (IBA), a precursor of the major endogenous auxin indole-3-acetic acid (IAA). When expressed in yeast, NPF7.3 mediated cellular IBA uptake. Loss-of-function npf7.3 mutants showed defective root gravitropism with reduced IBA levels and auxin responses. Nevertheless, the phenotype was restored by exogenous application of IAA but not by IBA treatment. NPF7.3 was expressed in pericycle cells and the root tip region including root cap cells of primary roots where the IBA-to-IAA conversion occurs. Our findings indicate that NPF7.3-mediated IBA uptake into specific cells is required for the generation of appropriate auxin gradients within root tissues.

Keywords: IBA; NPF; auxin; gravitropic response; transport.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anion Transport Proteins / metabolism*
  • Arabidopsis / drug effects
  • Arabidopsis / genetics
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / metabolism*
  • Biological Transport / drug effects
  • Biological Transport / genetics
  • Gene Expression Regulation, Plant / drug effects
  • Genetic Complementation Test
  • Gravitropism* / drug effects
  • Indoleacetic Acids / chemistry
  • Indoleacetic Acids / metabolism
  • Indoleacetic Acids / pharmacology
  • Indoles / chemistry
  • Indoles / metabolism*
  • Indoles / pharmacology
  • Mutation / genetics
  • Plant Roots / drug effects
  • Plant Roots / genetics
  • Plant Roots / growth & development*


  • Anion Transport Proteins
  • Arabidopsis Proteins
  • Indoleacetic Acids
  • Indoles
  • NRT1.5 protein, Arabidopsis
  • indolebutyric acid