Preprint Review Version 1 Preserved in Portico This version is not peer-reviewed

A Molecular Pinball Machine of the Plasma Membrane Regulates Plant Growth – A New Paradigm

Version 1 : Received: 8 July 2021 / Approved: 9 July 2021 / Online: 9 July 2021 (12:52:11 CEST)

How to cite: Lamport, D.T.; Tan, L.; Kieliszewski, M. A Molecular Pinball Machine of the Plasma Membrane Regulates Plant Growth – A New Paradigm. Preprints 2021, 2021070218 (doi: 10.20944/preprints202107.0218.v1). Lamport, D.T.; Tan, L.; Kieliszewski, M. A Molecular Pinball Machine of the Plasma Membrane Regulates Plant Growth – A New Paradigm. Preprints 2021, 2021070218 (doi: 10.20944/preprints202107.0218.v1).

Abstract

Novel molecular pinball machines of the plasma membrane control cytosolic Ca2+ levels that regulate plant metabolism. [https://youtu.be/zABg7LiBk88] Essential components involve: 1. an auxin-activated proton pump; 2. arabinogalactan glycoproteins (AGPs); 3. Ca2+ channels; 4. auxin-efflux “PIN” proteins. Typical pinball machines release pinballs that trigger various sound and visual effects. However, in plants “proton pinballs” eject Ca2+ bound by paired glucuronic acid residues of numerous glycomodules in periplasmic AGP-Ca2+. Freed Ca2+ ions flow down the electrostatic gradient through open Ca2+ channels into the cytosol thus activating numerous Ca2+-dependent activities.Clearly cytosolic Ca2+ levels depend on activity of the proton pump, the state of Ca2+ channels and size of the periplasmic AGP-Ca2+ capacitor: Proton pump activation is a major regulatory focal point tightly controlled by the supply of auxin: auxin efflux carriers conveniently known as “PIN” proteins [null mutants are pin-shaped!] pump auxin from cell to cell. Mechanosensitive Ca2+ channels and their activation by reactive oxygen species (ROS) are yet another factor regulating cytosolic Ca2+.Cell expansion also triggers proton pump/pinball activity by mechanotransduction of wall stress via Hechtian adhesion thus forming a Hechtian oscillator that underlies cycles of wall plasticity and oscillatory growth.Finally, Ca2+ homeostasis of plants depends on cell surface external storage as source of dynamic Ca2+, unlike the internal ER storage source of animals where the added regulatory complexities ranging from vitamin D to parathormone contrast with the elegant simplicity of plant life. This paper summarises a sixty year Odyssey.

Keywords

arabinogalactan proteins; proton pump; auxin; calcium signaling; Hechtian oscillator; PIN proteins; morphogenesis.

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