Plant and Cell Physiology Advance Access originally published online on June 3, 2009
Plant and Cell Physiology 2009 50(7):1319-1328; doi:10.1093/pcp/pcp076
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This article appears in the following Plant and Cell Physiology issue: Special Issue Articles: Omics and Bioinformatics [View the issue table of contents]
Vacuolar SNAREs Function in the Formation of the Leaf Vascular Network by Regulating Auxin Distribution
1Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan
*Corresponding author: E-mail, ihnishi{at}gr.bot.kyoto-u.ac.jp; Fax, +81-75-753-4142.
| Abstract |
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In normal leaf development, a two-dimensional pattern of leaf veins is known to form by differentiation of vascular cells from ground meristem cells in a manner that is regulated by the polar flow of auxin. However, the mechanisms regulating the distribution of auxin in the leaf primordium are largely unknown. Here we show that vacuolar SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors), VAM3 and VTI11, are required for the formation of the leaf vascular network in a dosage-dependent manner. This is the first report to show that the pre-vacuolar compartment (PVC)–vacuole traffic pathway is required for the formation of the leaf vascular network. vam3-4, a VAM3-defective mutant, was found to have an immature vascular network. An analysis of the DR5 reporter in vam3-4 indicated that VAM3 is involved in the proper pattern formation of auxin maxima in the leaf primordium. This suggests that the immature vascular network in vam3-4 was mainly determined at the stage of procambium formation in the leaf primordium. The abnormal distribution of auxin maxima was caused by the non-polarized localization of the auxin efflux carrier PIN1 (PIN-FORMED 1) in leaf primordium cells. VAM3 is the first key protein which is required for the proper localization of PIN1 in leaf cells. Finally, we found that PIN1 proteins were constitutively transported to vacuoles in leaf and roots cells. Our findings demonstrate that the PVC–vacuole pathway is required for the formation of auxin maxima, which regulates the polar localization of PIN1, which, in turn, is required for the formation of the leaf vascular network.
Keywords: Arabidopsis thaliana - Auxin - PIN1 - SNARE - VAM3 - Vascular network
Abbreviations: DAG, days after germination; GFP, green fluorescent protein; GUS, -glucuronidase; mRFP, monomeric red fluorescent protein; PIN1, PIN-FORMED 1; PVC, pre-vauolar compartment; RT–PCR, reverse transcription – PCR; SNARE, soluble N-ethylmaleimide-sensitive factor attachment protein receptor; TGN, trans-Golgi network; VAM, vacuolar morphology; VPS, vacuolar protein sorting; VTI, VPS 10 interacting.
2These authors contributed equally to this work.
(Received May 3, 2009; Accepted May 26, 2009)
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