Revealing the role of the plasma membrane H⁺-ATPase in plant adaptation to phosphorus deficiency in rice under various nitrogen sources and rhizosphere pH

Soil pH is critical for the bioavailability of nutrients and their consequent uptake by plant roots. This is specifically true for N and P, two key macronutrients that are essential for all aspects of plant growth and development. Importantly, availability of one nutrient can affect acquisition and translocation of another, although the mechanistic basis of this process remains unexplored. In this work, we combined a physiological (growth; ionomics), molecular (RNAseq and qPCR), biochemical (enzymatic assays) and genetic (using gain-of-function mutants) approaches to investigate the effect of interplay between P availability, two forms of N supply (NO₃⁻ vs NH₄⁺) and rhizosphere pH (3.0 vs 6.5) on rice plants. In general, rice plants grown in the presence of NH₄⁺ performed better than those treated with NO₃⁻ and better at pH 6.5 than at pH 3. P deprivation significantly reduced N accumulation in leaves but increased N in roots under both NH₄⁺ and NO₃⁻ treatments. Transcriptome analysis revealed 8749 differently expressed genes (DEGs) in leaves and 6519 DEGs in roots under P deprivation at pH 6.5, related to membrane function, cellular response, metabolism, and cell signaling. Among the DEGs, the plasma membrane H⁺-ATPase genes were significantly induced by both P deprivation under NO₃⁻ and NH₄⁺ treatments, indicating a possible role of H⁺-ATPase in plant adaptive responses to P nutrition. The latter was confirmed in direct experiments combining ³³P radiotracers. Overexpression of OSA1 encoding a H⁺-ATPase improved nutrient uptake and rice growth. Overall, these results suggest that PM H⁺-ATPase plays a crucial role in the regulation of N and P uptake and provide a new approach to develop crop varieties that are more efficient at absorbing and utilizing nutrients and, hence, capable to achieve optimal yields.