OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) Supplemental Data OA All Versions of this Article: 19/6/1838    most recent tpc.107.051599v1 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 ISI 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 ISI Web of Science (13) Citing Articles via Google Scholar Google Scholar Articles by Lewis, D. R. Articles by Spalding, E. P. Search for Related Content PubMed PubMed Citation Articles by Lewis, D. R. Articles by Spalding, E. P. Agricola Articles by Lewis, D. R. Articles by Spalding, E. P.

Separating the Roles of Acropetal and Basipetal Auxin Transport on Gravitropism with Mutations in Two Arabidopsis Multidrug Resistance-Like ABC Transporter Genes^[W],[OA]

^a Department of Botany, University of Wisconsin, Madison, Wisconsin 53706
^b Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin 53706

¹ To whom correspondence should be addressed. E-mail spalding{at}wisc.edu; fax 608-262-7509.

Two Arabidopsis thaliana ABC transporter genes linked to auxin transport by various previous results were studied in a reverse-genetic fashion. Mutations in Multidrug Resistance-Like1 (MDR1) reduced acropetal auxin transport in roots by 80% without affecting basipetal transport. Conversely, mutations in MDR4 blocked 50% of basipetal transport without affecting acropetal transport. Developmental and auxin distribution phenotypes associated with these altered auxin flows were studied with a high-resolution morphometric system and confocal microscopy, respectively. Vertically grown mdr1 roots produced positive and negative curvatures threefold greater than the wild type, possibly due to abnormal auxin distribution observed in the elongation zone. However, upon 90° reorientation, mdr1 gravitropism was inseparable from the wild type. Thus, acropetal auxin transport maintains straight growth but contributes surprisingly little to gravitropism. Conversely, vertically maintained mdr4 roots grew as straight as the wild type, but their gravitropism was enhanced. Upon reorientation, curvature in this mutant developed faster, was distributed more basally, and produced a greater total angle than the wild type. An amplified auxin asymmetry may explain the mdr4 hypertropism. Double mutant analysis indicated that the two auxin transport streams are more independent than interdependent. The hypothesis that flavanols regulate MDR-dependent auxin transport was supported by the epistatic relationship of mdr4 to the tt4 phenylpropanoid pathway mutation.

This article has been cited by other articles:

				D. Santelia, S. Henrichs, V. Vincenzetti, M. Sauer, L. Bigler, M. Klein, A. Bailly, Y. Lee, J. Friml, M. Geisler, et al. Flavonoids Redirect PIN-mediated Polar Auxin Fluxes during Root Gravitropic Responses J. Biol. Chem., November 7, 2008; 283(45): 31218 - 31226. [Abstract] [Full Text] [PDF]

				B. Titapiwatanakun and A. S. Murphy Post-transcriptional regulation of auxin transport proteins: cellular trafficking, protein phosphorylation, protein maturation, ubiquitination, and membrane composition J. Exp. Bot., September 29, 2008; (2008) ern240v1. [Abstract] [Full Text] [PDF]

				D. K. Owens, A. B. Alerding, K. C. Crosby, A. B. Bandara, J. H. Westwood, and B. S.J. Winkel Functional Analysis of a Predicted Flavonol Synthase Gene Family in Arabidopsis Plant Physiology, July 1, 2008; 147(3): 1046 - 1061. [Abstract] [Full Text] [PDF]

				M. Cho, S. H. Lee, and H.-T. Cho P-Glycoprotein4 Displays Auxin Efflux Transporter-Like Action in Arabidopsis Root Hair Cells and Tobacco Cells PLANT CELL, December 1, 2007; 19(12): 3930 - 3943. [Abstract] [Full Text] [PDF]

				C. S. Buer, G. K. Muday, and M. A. Djordjevic Flavonoids Are Differentially Taken Up and Transported Long Distances in Arabidopsis Plant Physiology, October 1, 2007; 145(2): 478 - 490. [Abstract] [Full Text] [PDF]

				G. Wu, D. R. Lewis, and E. P. Spalding Mutations in Arabidopsis Multidrug Resistance-Like ABC Transporters Separate the Roles of Acropetal and Basipetal Auxin Transport in Lateral Root Development PLANT CELL, June 1, 2007; 19(6): 1826 - 1837. [Abstract] [Full Text] [PDF]