Abstract
A facilitated nitrite transport is involved in the nitrite reduction in higher plants. We first cloned cDNA (CsNitr1-L) for a nitrite transporter of chloroplst envelope. CsNitr1-L shows Km for nitrite of ~0.1 mM being classified as an high-affinity type. Arabidopsis mutants with only one putative nitrite transporter disrupted accumulated nitrite 20-times as much as wild type, showed a phenotype of N deficiency, however, grew with nitrate as sole N source. Nitrite uptake of the mutants was examined by incubating leaf discs with various concentrations of nitrite on illumination. High- affinity nitrite uptake was shown to be lost in the mutants. In contrast, the mutant absorbed nitrite faster than wild type from the media that contained nitrite of unusually high concentration. Accumulated nitrite may induce a low affinity nitrite uptake in Arabidopsis mutants when the plant loses the high affinity one functioning in the uptake of nitrite of physiological concentration.
