OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) Supplemental Data OA All Versions of this Article: 148/2/870    most recent pp.108.119396v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Schuetz, M. Articles by Mattsson, J. Search for Related Content PubMed PubMed Citation Articles by Schuetz, M. Articles by Mattsson, J. Agricola Articles by Schuetz, M. Articles by Mattsson, J.

DEVELOPMENT AND HORMONE ACTION

Multiple MONOPTEROS-Dependent Pathways Are Involved in Leaf Initiation^{1,[C],[W],[OA]}

Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6 (M.S., J.M.); and Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 1A1 (T.B.)

Initiation of leaves at the flanks of the shoot apical meristem occurs at sites of auxin accumulation and pronounced expression of auxin-inducible PIN-FORMED1 (PIN) genes, suggesting a feedback loop to progressively focus auxin in concrete spots. Because PIN expression is regulated by auxin response factor activity, including MONOPTEROS (MP), it appeared possible that MP affects leaf formation as a positive regulator of PIN genes and auxin transport. Here, we analyze a novel, completely leafless phenotype arising from simultaneous interference with both auxin signaling and auxin transport. We show that mp pin1 double mutants, as well as mp mutants treated with auxin-efflux inhibitors, display synergistic abnormalities not seen in wild type regardless of how strongly auxin transport was reduced. The synergism of abnormalities indicates that the role of MP in shoot meristem organization is not limited to auxin transport regulation. In the mp mutant background, auxin transport inhibition completely abolishes leaf formation. Instead of forming leaves, the abnormal shoot meristems dramatically increase in size, harboring correspondingly enlarged expression domains of CLAVATA3 and SHOOTMERISTEMLESS, molecular markers for the central stem cell zone and the complete meristem, respectively. The observed synergism under conditions of auxin efflux inhibition was further supported by an unrestricted PIN1 expression in mp meristems, as compared to a partial restriction in wild-type meristems. Auxin transport-inhibited mp meristems also lacked detectable auxin maxima. We conclude that MP promotes the focusing of auxin and leaf initiation in part through pathways not affected by auxin efflux inhibitors.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Jim Mattsson (mattsson{at}sfu.ca).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.119396

^* Corresponding author; e-mail mattsson{at}sfu.ca.

Received March 25, 2008; accepted July 2, 2008; published August 8, 2008.

This article has been cited by other articles:

				T. J. Donner, I. Sherr, and E. Scarpella Regulation of preprocambial cell state acquisition by auxin signaling in Arabidopsis leaves Development, October 1, 2009; 136(19): 3235 - 3246. [Abstract] [Full Text] [PDF]

				S. E. Ploense, M.-F. Wu, P. Nagpal, and J. W. Reed A gain-of-function mutation in IAA18 alters Arabidopsis embryonic apical patterning Development, May 1, 2009; 136(9): 1509 - 1517. [Abstract] [Full Text] [PDF]

				T. Girin, K. Sorefan, and L. Ostergaard Meristematic sculpting in fruit development J. Exp. Bot., April 1, 2009; 60(5): 1493 - 1502. [Abstract] [Full Text] [PDF]