Journal
PLANT JOURNAL
Volume 73, Issue 5, Pages 709-719Publisher
WILEY
DOI: 10.1111/tpj.12074
Keywords
exocyst; polar auxin transport; PIN recycling; EXO70A1 subunit; Arabidopsis thaliana
Categories
Funding
- Czech Science Foundation [GACR P501/11/P853, P305/11/1629]
- Ministry of Education, Youth and Sports of the Czech Republic [KONTAKT ME10033, MSMT LC06034, MSM0021620858]
- Grant Agency of the Academy of Sciences of the Czech Republic [KJB600380802]
- US National Science Foundation [IOS 0820648]
- Direct For Biological Sciences
- Division Of Integrative Organismal Systems [0920747] Funding Source: National Science Foundation
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In land plants polar auxin transport is one of the substantial processes guiding whole plant polarity and morphogenesis. Directional auxin fluxes are mediated by PIN auxin efflux carriers, polarly localized at the plasma membrane. The polarization of exocytosis in yeast and animals is assisted by the exocyst: an octameric vesicle-tethering complex and an effector of Rab and Rho GTPases. Here we show that rootward polar auxin transport is compromised in roots of Arabidopsis thaliana loss-of-function mutants in the EXO70A1 exocyst subunit. The recycling of PIN1 and PIN2 proteins from brefeldinA compartments is delayed after the brefeldin-A washout in exo70A1 and sec8 exocyst mutants. Relocalization of PIN1 and PIN2 proteins after prolonged brefeldin-A treatment is largely impaired in these mutants. At the same time, however, plasma membrane localization of GFP:EXO70A1, and the other exocyst subunits studied (GFP:SEC8 and YFP:SEC10), is resistant to brefeldin-A treatment. In root cells of the exo70A1 mutant, a portion of PIN2 is internalized and retained in specific, abnormally enlarged, endomembrane compartments that are distinct from VHA-a1-labelled early endosomes or the trans-Golgi network, but are RAB-A5d positive. We conclude that the exocyst is involved in PIN1 and PIN2 recycling, and thus in polar auxin transport regulation.
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