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The proline 160 in the selectivity filter of the Arabidopsis NO 3 − /H + exchanger AtCLCa is essential for nitrate accumulation in planta
Author(s) -
Wege Stefanie,
Jossier Mathieu,
Filleur Sophie,
Thomine Sébastien,
BarbierBrygoo Hélène,
Gambale Franco,
De Angeli Alexis
Publication year - 2010
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2010.04288.x
Subject(s) - proline , arabidopsis , nitrate , selectivity , chemistry , botany , biochemistry , biology , gene , organic chemistry , catalysis , amino acid , mutant
Summary Nitrate, the major nitrogen source for plants, can be accumulated in the vacuole. Its transport across the vacuolar membrane is mediated by AtCLCa, an antiporter of the chloride channel (CLC) protein family. In contrast to other CLC family members, AtCLCa transports nitrate coupled to protons. Recently, the different behaviour towards nitrate of CLC proteins has been linked to the presence of a serine or proline in the selectivity filter motif GXGIP. By monitoring AtCLCa activity in its native environment, we show that if proline 160 in AtCLCa is changed to a serine (AtCLCa P160S ), the transporter loses its nitrate selectivity, but the anion proton exchange mechanism is unaffected. We also performed in vivo analyses in yeast and Arabidopsis. In contrast to native AtCLCa , expression of AtCLCa P160S does not complement either the Δ ScCLC yeast mutant grown on nitrate or the nitrate under‐accumulation phenotype of clca knockout plants. Our results confirm the significance of this amino acid in the conserved selectivity filter of CLC proteins and highlight the importance of the proline in AtCLCa for nitrate metabolism in Arabidopsis.