An Arabidopsis quiescin-sulfhydryl oxidase regulates cation homeostasis at the root symplast-xylem interface.
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 QSO2Colon, two colonsGFP 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.
Alejandro
Santiago
S
Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Camino de Vera s/n, Valencia, Spain.
Rodríguez
Pedro L
PL
Bellés
Jose M
JM
Yenush
Lynne
L
García-Sanchez
María J
MJ
Fernández
José A
JA
Serrano
Ramón
R
D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002412:Cations / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011188:Potassium / Q000737:chemistry / Q000378:metabolism; D012680:Sensitivity and Specificity; D013095:Spermidine / Q000031:analogs & derivatives / Q000494:pharmacology; D052584:Xylem / Q000378:metabolism*
D029681:Arabidopsis Proteins; D002412:Cations; D018744:DNA, Plant; C006760:norspermidine; D050862:Oxidoreductases Acting on Sulfur Group Donors; C524351:QSO2 protein, Arabidopsis; D011188:Potassium; D013095:Spermidine