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  • The EMBO Journal (2007) 26, 3203 - 3215
  • doi:10.1038/sj.emboj.7601757

Published online: 14 June 2007

An Arabidopsis quiescin-sulfhydryl oxidase regulates cation homeostasis at the root symplast–xylem interface

Santiago Alejandro1, Pedro L Rodríguez1, Jose M Bellés1, Lynne Yenush1, María J García-Sanchez2, José A Fernández2 and Ramón Serrano1

  1. Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Camino de Vera s/n, Valencia, Spain
  2. Departamento de Biología Vegetal, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, Málaga, Spain

Correspondence to:

Ramón Serrano, Instituto de Biología Molecular y Celular de Plantas, Universidad Politecnica de Valencia-CSIC, Camino de Vera s/n, Valencia 46022, Spain. Tel.: +34 96 387 7883; Fax: +34 96 387 7859; E-mail: rserrano@ibmcp.upv.es

Received 22 January 2007; Accepted 18 May 2007

A genetic screen of Arabidopsis 'activation-tagging' mutant collection based on tolerance to norspermidine resulted in a dominant mutant (par1-1D) with increased expression of the QSO2 gene (At1g15020), encoding a member of the quiescin-sulfhydryl oxidase (QSO) family. The par1-1D mutant and transgenic plants overexpressing QSO2 cDNA grow better than wild-type Arabidopsis in media with toxic cations (polyamines, Li+ and Na+) or reduced K+ concentrations. This correlates with a decrease in the accumulation of toxic cations and an increase in the accumulation of K+ in xylem sap and shoots. Conversely, three independent loss-of-function mutants of QSO2 exhibit phenotypes opposite to those of par1-1D. QSO2 is mostly expressed in roots and is upregulated by K+ starvation. A QSO2double colonGFP fusion ectopically expressed in leaf epidermis localized at the cell wall. The recombinant QSO2 protein, produced in yeast in secreted form, exhibits disulfhydryl oxidase activity. A plausible mechanism of QSO2 action consists on the activation of root systems loading K+ into xylem, but different from the SKOR channel, which is not required for QSO2 action. These results uncover QSOs as novel regulators of ion homeostasis.

  • Keywords:

    • activation-tagging,
    • K+ transport,
    • salinity,
    • red-ox regulation