Involvement of <i>CsNRT1.7</i> in nitrate recycling during senescence in cucumber

Abstract

Abstract A senescence‐induced gene named CsNRT1.7 was cloned from a cucumber cultivar with high capacity for low‐N tolerance using a homologous cloning technique based on bioinformatics analysis and cucumber genome information. The full‐length cDNA of CsNRT1.7 was 1803 bp with an open reading frame encoding 601 amino acids. Homology analysis showed that CsNRT1.7 had high homology (74%) to the Arabidopsis nitrate transporter gene NRT1.7. Phylogenetic analysis indicated that CsNRT1.7 had a close relationship with NRT1.7 among different nitrate transporters in Arabidopsis. Quantitative RT‐PCR and CsNRT1.7pro:GUS reporter analysis showed that CsNRT1.7 was a senescence‐induced gene, whose transcription was much stronger in old leaf, followed by mature leaf and young leaf of cucumber plants. CsNRT1.7 could also be induced by low‐nitrogen treatment. The transient expression of CsNRT1.7:EGFP in onion epidermal cells indicated that CsNRT1.7 was localized in the plasma membrane. Further functional analysis revealed that 35S:CsNRT1.7/nrt1.7‐2 transgenic Arabidopsis plants showed lower nitrate content and larger leaf size than nrt1.7‐2 T‐DNA insertion Arabidopsis plants. These results provide new clues to further understand the function of CsNRT1.7 regarding senescence‐regulated low‐nitrogen tolerance in cucumber.