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Review
. 2002 Feb;14(2):293-9.
doi: 10.1105/tpc.140230.

An emerging model of auxin transport regulation

Gloria K Muday  1 , Angus S Murphy
Collaborators, Affiliations
Review

An emerging model of auxin transport regulation

Gloria K Muday et al. Plant Cell. 2002 Feb.
No abstract available

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Figures

Figure 1.
Figure 1.
Model of Experiments That Have Examined the Mechanisms of the Control of PIN1 Protein Localization. (A) Vesicle-dependent transport of the PIN1 protein to the basal membrane appears to be along actin tracks. A high-affinity NPA binding protein has been found to interact with actin and may act as a bridge between these transport vesicles and the actin tracks and/or may serve to localize PIN1-containing IAA efflux complexes to the basal membrane. (B) Treatment with cytochalasin leads to a random PIN1 protein distribution and reduces polar auxin transport. (C) Treatment with BFA leads to a loss of PIN1 protein on the membrane and an accumulation of PIN1 protein at two undefined internal membrane structures. The effect is reversible upon removal of the BFA. (D) Treatment with either cytochalasin or the IAA efflux inhibitor TIBA during the removal of BFA prevents the restoration of asymmetric PIN1 distribution. Treatment with either cytochalasin or TIBA before BFA treatment prevents the BFA-induced PIN1 internalization, and treatment with TIBA alone has no effect on PIN1 localization (data not shown). (This figure was modified from Muday and DeLong [2001]).
Figure 2.
Figure 2.
The Mammalian GLUT4 Asymmetric Vesicular Targeting Mechanism as a Model for the Localization of the Auxin Efflux Carrier. A vesicular cycling mechanism similar to the mammalian insulin-inducible GLUT4 glucose transporter trafficking system is suggested by recent studies of PIN protein localization and protein interactions with auxin transport inhibitors. Sequence homologies and analogous functions of many of the protein components of the two systems further suggest parallel mechanisms. An external signal (hormone binding) triggers a phosphatidylinositol/phosphorylation cascade that activates asymmetric vesicular trafficking by (1) causing relocation of an inhibitory ARF-GEF protein (GRP1 or GNOM) from an endomembrane compartment to phosphatidylinositol triphosphate-enriched plasma membranes and (2) phosphorylating both a vesicular aminopeptidase (IRAP or AtAPM1) and the Vamp2 adaptor protein. Vesicles then traffic on actin filaments to a plasma membrane docking site, where Vamp2 interacts with Syntaxin 4/Knolle to initiate docking with Munc18c/Keule and subsequent vesicle fusion. Endocytotic vesicles enriched in dynamin and β-adaptin traffic back to the endosomal compartment in a similar actin-dependent manner. AtAPM1, Arabidopsis thaliana microsomal aminopeptidase; GRP1 ARF-GEF, general receptor for phosphoinositides ADP ribosylation factor guanine nucleotide exchange factor; IRAP, insulin-responsive aminopeptidase; Munc18c, mammalian homolog of unc18c; PID, PINOID; PI3K, phosphatidylinositol 3-kinase; PKB, protein kinase B/KT; PKC, protein kinase C; PP2a, phosphatase 2a; RCN1, root curling in NPA-1 PP2a; Vamp2, vesicle-associated membrane protein 2 (v-SNARE2).
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References

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