Preprint Article Version 1 This version is not peer-reviewed

Relative Contribution of PIN-containing Secretory Vesicles and Plasma Membrane PINs to the Directed Auxin Transport: Theoretical Estimation

Version 1 : Received: 17 September 2018 / Approved: 18 September 2018 / Online: 18 September 2018 (10:09:24 CEST)

A peer-reviewed article of this Preprint also exists.

Hille, S.; Akhmanova, M.; Glanc, M.; Johnson, A.; Friml, J. Relative Contribution of PIN-Containing Secretory Vesicles and Plasma Membrane PINs to the Directed Auxin Transport: Theoretical Estimation. Int. J. Mol. Sci. 2018, 19, 3566. Hille, S.; Akhmanova, M.; Glanc, M.; Johnson, A.; Friml, J. Relative Contribution of PIN-Containing Secretory Vesicles and Plasma Membrane PINs to the Directed Auxin Transport: Theoretical Estimation. Int. J. Mol. Sci. 2018, 19, 3566.

Journal reference: Int. J. Mol. Sci. 2018, 19, 3566
DOI: 10.3390/ijms19113566

Abstract

Intercellular transport of auxin is driven by PIN-formed (PIN) proteins. PINs are localized at the plasma membrane (PM) and on constitutively recycling endomembrane vesicles. Therefore, PINs can mediate auxin transport either by direct translocation across the PM or by pumping it into secretory vesicles (SVs), leading to its secretory release upon fusion with the PM. Which of these two mechanisms dominates is a matter of debate. Here we addressed the issue with a mathematical modeling approach. We demonstrate that the efficiency of secretory transport depends on SV size, half-life of PINs on the PM, pH, exocytosis frequency and PIN density. 3D-SIM microscopy was used to determine PIN density on the PM. Combing this data with published values of the other parameters, we show that the transport activity of PINs in SVs would have to be at least 1000x greater than on the PM in order to produce a comparable macroscopic auxin transport. If both transport mechanisms operated simultaneously and PINs were equally active on SVs and PM, the contribution of secretion to the total auxin flux would be negligible. In conclusion, while secretory vesicle-mediated transport of auxin is intriguing and theoretically possible model, it unlikely to be a major mechanism of auxin transport in planta.

Subject Areas

Polar Auxin Transport; PIN transporters; Secretion; 3D-SIM microscopy; Mathematical modeling

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