Study of the interplay between the V-PPase and tonoplast-localise NHX antiporters in ion and pH homeostasis

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The tonoplast-localise NHX1 and NHX2 exchangers are cation/H+ antiporters involved in K+ nutrition, Na+ tolerance and pH homeostasis. To function, NHX antiporters need a H+ gradient across the tonoplast that in plant cells is generated by the combined action of two H+-pumps, the vacuolar H+-ATPase (V-ATPase) and the vacuolar H+-pyrophosphatase (V-PPase). Thus, ubiquitous overexpression of the V-PPase, the NHX exchangers or a combination of both has been a largely used strategy to create tolerant plants to abiotic stresses. However, the mechanism by which the beneficial traits are gained in the transgenic lines remains unknown. Our preliminary data show that the V-PPase and the NHX proteins physically interact and depend on each other to control potassium homeostasis and cell elongation. Additionally, the results suggest a main role of the V-PPase in the stomatal movements kinetics. Therefore, my main goal is to investigate how the tonoplast V-PPase and NHX transporters coordinate their activities to maintain ion and pH homeostasis under different external conditions. First I will study how their functional and physical interactions and their post-transcriptional modifications influence plant growth and development. Second, I will investigate the role of the V-PPase in guard cell function and its connection with stress tolerance responses.