Preprint Review Version 1 Preserved in Portico This version is not peer-reviewed

The Growth Oscillator and Plant Stomata: an Open and Shut Case

Version 1 : Received: 19 May 2023 / Approved: 22 May 2023 / Online: 22 May 2023 (08:55:24 CEST)

How to cite: Lamport, D. T. The Growth Oscillator and Plant Stomata: an Open and Shut Case. Preprints 2023, 2023051479. https://doi.org/10.20944/preprints202305.1479.v1 Lamport, D. T. The Growth Oscillator and Plant Stomata: an Open and Shut Case. Preprints 2023, 2023051479. https://doi.org/10.20944/preprints202305.1479.v1

Abstract

Since Darwin’s “Power of movement in plants” the precise mechanism of oscillatory plant growth remains elusive. Hence the search continues for the hypothetical growth oscillator that regulates a huge range of growth phenomena ranging from circumnutation to pollen tube tip growth and stomatal movements. Oscillators are essentially simple devices with few components. A universal growth oscillator with only four major components became apparent recently with the discovery of a missing component, notably arabinogalactan glycoproteins (AGPs) that store dynamic Ca2+ at the cell surface. Demonstrably, auxin-activated proton pumps, AGPs, Ca2+ channels and auxin efflux “PIN” proteins, embedded in the plasma membrane, combine to generate cytosolic Ca2+ oscillations that ultimately regulate oscillatory growth: Hechtian adhesion of the plasma membrane to the cell wall and auxin-activated proton pumps trigger the release of dynamic Ca2+ stored in periplasmic AGP monolayers. These four major components represent a molecular PINball machine a strong visual metaphor that also recognizes auxin efflux “PIN” proteins as an essential component. Proton “pinballs” dissociate Ca2+ ions bound by paired glucuronic acid residues of AGP glycomodules, hence reassesses the role of proton pumps. It shifts the prevalent paradigm away from the recalcitrant “acid growth” theory that proposes direct action on cell wall properties, with an alternative explanation that connects proton pumps to Ca2+ signaling with dynamic Ca2+ storage by AGPs, auxin transport by auxin-efflux PIN proteins and Ca2+ channels. The extensive Ca2+ signalling literature of plants ignores arabinogalactan proteins (AGPs). Such scepticism leads us to reconsider the validity of the universal growth oscillator proposed here with some exceptions that involve marine plants and perhaps the most complex stress-test, stomatal regulation.

Keywords

calcium homeostasis; AGPs; proton pump; cell wall

Subject

Biology and Life Sciences, Plant Sciences

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