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Plasma membrane intrinsic proteins PIP1;1 and PIP1;3 contribute to the tolerance to nitrogen deficiency in potato

Nitrogen (N) deficiency is one of the major constraints for potato (Solanum tuberosum L.) production, due to its shallow root system and poor capabilities of N mobilization from the deeper layers of the soil. The aim of this study was to elucidate plasma membrane (PM) proteins potentially involved in the tolerance towards N deficiency. We compared the PM proteome of the two potato cultivars ‘Lambada’ and ‘Topas’, contrasting in their N deficiency response under in vitro conditions. Using mass spectrometry we identified 65 proteins, which were differentially abundant in the two cultivars when submitted to N deficiency. Amongst those, candidate proteins were selected based on their potential to be involved in N transport under deficient conditions. Two members of the aquaporin family, StPIP1;1 and StPIP1;3, were studied in more detail. By means of a yeast growth assay we showed that these proteins do not facilitate transport of ammonia. The Arabidopsis (Arabidopsis thaliana) knockout mutants AtPIP1;1 and AtPIP1;3 showed a reduced N content and accumulation of anthocyanins under N deficiency. We conclude that PIP1;1 and PIP1;3 are indirectly involved in the N uptake under N deficient conditions and contribute to an increased N deficiency tolerance.