Growth signaling by the plant peptide phytosulfokine

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Plant growth is regulated by phytohormones and peptide signals. The number of peptides that are identified and shown to regulate gowth and development in plants is steadily increasing. Yet, we know comparatively little about peptide mobility and their mode of action. In this project we will study these aspects using the peptide growth factor phytosulfokine (PSK). We will answer the question if PSK acts locally or can be active as a long-distance signal for instance in root to shoot communication. We know that PSK is perceived at the plant cell surface by a membrane-bound receptor. Recent research in our group indicated that the PSK receptor is part of a nanocluster together with a proton pump, a cation channel, and likely a water channel. These proteins play crucial roles in plant cell growth. Taken together, it appears that PSK signaling activates a proton pump to cause cell wall relaxation, opens a cation channel to increase osmotic potential, and facilitates water influx to actually make the cell expand. However, these are hypotheses that need verification. In this project we will study if and how PSK regulates ion and water translocating membrane proteins to promote plant cell growth.