title: Compensatory mutations in predicted metal transporters modulate auxin conjugate responsiveness in Arabidopsis.
abstract: Levels of the phytohormone indole-3-acetic acid (IAA) can be altered by the formation and hydrolysis of IAA conjugates. The isolation and characterization of Arabidopsis thaliana mutants with reduced IAA-conjugate sensitivity and wild-type IAA responses is advancing the understanding of auxin homeostasis by uncovering the factors needed for conjugate metabolism. For example, the discovery that the IAA-Ala-resistant mutant iar1 is defective in a protein in the ZIP family of metal transporters uncovered a link between metal homeostasis and IAA-conjugate sensitivity. To uncover additional factors impacting auxin conjugate metabolism, we conducted a genetic modifier screen and isolated extragenic mutations that restored IAA-amino acid conjugate sensitivity to the iar1 mutant. One of these suppressor mutants is defective in a putative cation diffusion facilitator, MTP5 (At3g12100; formerly known as MTPc2). Loss of MTP5 function restored IAA conjugate sensitivity to iar1 but not to mutants defective in IAA-amino acid conjugate amidohydrolases. Our results are consistent with a model in which MTP5 and IAR1 transport metals in an antagonistic fashion to regulate metal homeostasis within the subcellular compartment in which the IAA-conjugate amidohydrolases reside, and support previous suggestions that the ion composition in this compartment influences hydrolase activity.
authors: Department of Biology, Harding University, Searcy, Arkansas 72149, USA.
authors: Rebekah A
authors: RA
authors: Rampey
authors: Megan T
authors: MT
authors: Baldridge
authors: David C
authors: DC
authors: Farrow
authors: Sarah N
authors: SN
authors: Bay
authors: Bonnie
authors: B
authors: Bartel
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D003433:Crosses, Genetic; D006706:Homeostasis / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation / Q000235:genetics; D009841:Oligonucleotides / Q000235:genetics; D016133:Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D007210:Indoleacetic Acids; C581835:MTP5 protein, Arabidopsis; D008670:Metals; D009841:Oligonucleotides; C030737:indoleacetic acid
keywords: Arabidopsis; IAR1; MTP5; auxin conjugates; metal transport