Potassium carrier TRH1 is required for auxin transport in Arabidopsis roots.
Disruption of the TRH1 potassium transporter impairs root hair development in Arabidopsis, and also affects root gravitropic behaviour. Rescue of these morphological defects by exogenous auxin indicates a link between TRH1 activity and auxin transport. In agreement with this hypothesis, the rate of auxin translocation from shoots to roots and efflux of [3H]IAA in isolated root segments were reduced in the trh1 mutant, but efflux of radiolabelled auxin was accelerated in yeast cells transformed with the TRH1 gene. In roots, Pro(TRH1):GUS expression was localized to the root cap cells which are known to be the sites of gravity perception and are central for the redistribution of auxin fluxes. Consistent with these findings, auxin-dependent DR5:GUS promoter-reporter construct was misexpressed in the trh1 mutant indicating that partial block of auxin transport through the root cap is associated with upstream accumulation of the phytohormone in protoxylem cells. When [K+] in the medium was reduced from 20 to 0.1 mm, wild type roots showed mild agravitropic phenotype and DR5:GUS misexpression in stelar cells. This pattern of response to low external [K+] was also affected by trh1 mutation. We conclude that the TRH1 carrier is an important part of auxin transport system in Arabidopsis roots.
Vicente-Agullo
Francisco
F
Department of Agricultural Sciences, Imperial College London, Wye Campus, Wye, Ashford, Kent TN25 5AH, UK.
Rigas
Stamatis
S
Desbrosses
Guilhem
G
Dolan
Liam
L
Hatzopoulos
Polydefkis
P
Grabov
Alexander
A
D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001693:Biological Transport, Active / Q000235:genetics; D027682:Cation Transport Proteins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D018522:Gravitropism / Q000235:genetics; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D009154:Mutation; D030781:Organisms, Genetically Modified; D010641:Phenotype; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000378:metabolism
D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D007210:Indoleacetic Acids; C474309:TRH1 protein, Arabidopsis; D011188:Potassium