Dual regulation of root hydraulic conductivity and plasma membrane aquaporins by plant nitrate accumulation and high-affinity nitrate transporter NRT2.1.

The water status and mineral nutrition of plants critically determine their growth and development. Nitrate (NO3 (-)), the primary nitrogen source of higher plants, is known to impact the water transport capacity of roots (root hydraulic conductivity,Lpr). To explore the effects and mode of action of NO3 (-)onLpr, we used an extended set of NO3 (-)transport (nrt1.1,nrt1.2,nrt1.5andnrt2.1), signaling (nrt1.1andnrt2.1) and metabolism (nia) mutants in Arabidopsis, grown under various NO3 (-)conditions. First, a strong positive relationship betweenLprand NO3 (-)accumulation, in shoots rather than in roots, was revealed. Secondly, a specific 30% reduction ofLprinnrt2.1plants unraveled a major role for the high-affinity NO3 (-)transporter NRT2.1 in increasingLpr These results indicate that NO3 (-)signaling rather than nitrogen assimilation products governsLprin Arabidopsis. Quantitative real-time reverse transcription-PCR and enzyme-linked immunosorbent assays (ELISAs) were used to investigate the effects of NO3 (-)availability on plasma membrane aquaporin (plasma membrane intrinsic protein; PIP) expression. Whereas PIP regulation mostly occurs at the post-translational level in wild-type plants, a regulation of PIPs at both the transcriptional and translational levels was uncovered innrt2.1plants. In conclusion, this work reveals that control of ArabidopsisLprand PIP functions by NO3 (-)involves novel shoot to root signaling and NRT2.1-dependent functions.

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