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

作者：Alejandro Santiago; Rodriguez Pedro L; Belles Jose M; Yenush Lynne; Garcia Sanchez Maria J; Fernandez Jose A; Serrano Ramon^*

来源：The EMBO Journal, 2007, 26(13): 3203-3215.

DOI：10.1038/sj.emboj.7601757

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

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 QSO2 :: HGFP 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.

• 出版日期2007-7-11