--- res: bibo_abstract: - The intercellular transport of auxin is driven by PIN-formed (PIN) auxin efflux carriers. 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 auxin 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 structured illumination microscopy (SIM) was used to determine PIN density on the PM. Combining 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 1000× 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 an intriguing and theoretically possible model, it is unlikely to be a major mechanism of auxin transport inplanta.@eng bibo_authorlist: - foaf_Person: foaf_givenName: Sander foaf_name: Hille, Sander foaf_surname: Hille - foaf_Person: foaf_givenName: Maria foaf_name: Akhmanova, Maria foaf_surname: Akhmanova foaf_workInfoHomepage: http://www.librecat.org/personId=3425EC26-F248-11E8-B48F-1D18A9856A87 orcid: 0000-0003-1522-3162 - foaf_Person: foaf_givenName: Matous foaf_name: Glanc, Matous foaf_surname: Glanc foaf_workInfoHomepage: http://www.librecat.org/personId=1AE1EA24-02D0-11E9-9BAA-DAF4881429F2 orcid: 0000-0003-0619-7783 - foaf_Person: foaf_givenName: Alexander J foaf_name: Johnson, Alexander J foaf_surname: Johnson foaf_workInfoHomepage: http://www.librecat.org/personId=46A62C3A-F248-11E8-B48F-1D18A9856A87 orcid: 0000-0002-2739-8843 - foaf_Person: foaf_givenName: Jirí foaf_name: Friml, Jirí foaf_surname: Friml foaf_workInfoHomepage: http://www.librecat.org/personId=4159519E-F248-11E8-B48F-1D18A9856A87 orcid: 0000-0002-8302-7596 bibo_doi: 10.3390/ijms19113566 bibo_issue: '11' bibo_volume: 19 dct_date: 2018^xs_gYear dct_identifier: - UT:000451528500282 dct_isPartOf: - http://id.crossref.org/issn/1422-0067 dct_language: eng dct_publisher: MDPI@ dct_title: 'Relative contribution of PIN-containing secretory vesicles and plasma membrane PINs to the directed auxin transport: Theoretical estimation@' ...