combination of genetic and biochemical approaches. These findings offer tremendous in-
sight into the novel mechanisms that control the synthesis, targeting, activity, as well as
the proteolytic degradation of proteins that act in concert to drive auxin redistribution.
Finally, the understanding of how the auxin signal is transduced to control synthesis of
proteins needed for asymmetric growth rounds out our understanding of how the asym-
metries in auxin induce differential growth.
3.9 Acknowledgments
Several grants facilitated this work, with GKM supported by the U.S. Department of
Agriculture (No. 2006-35304-17311) and AR supported by the National Science
Foundation (IBN 0316876).
3.10 Literature cited
Abas, L., R. Benjamins, N. Malenica, T. Paciorek, J. Wisniewska, J. C. Moulinier-Anzola, T.
Sieberer, J. Friml and C. Luschnig. 2006. Intracellular Trafficking and Proteolysis of the
ArabidopsisAuxin-Efflux Facilitator PIN2 Are Involved in Root Gravitropism. Nat Cell Biol8:
249–56.
Abel, S., M. Nguyen, W. Chow and A. Theologis. 1995. Asc4, a Primary Indoleacetic Acid-
Responsive Gene Encoding 1-Aminocyclopropane-1-Carboxylate Synthase in Arabidopsis
thaliana.J Biol Chem270: 19093–99.
Allan, A. C. and P. H. Rubery. 1991. Calcium Deficiency and Auxin Transport in Cucurbita pepo
L. Seedlings. Planta183: 604–12.
Becker, D. and R. Hedrich. 2002. Channelling Auxin Action: Modulation of Ion Transport by
Indole-3-Acetic Acid. Plant Mol Biol49: 349–56.
Benjamins, R., N. Malenica and C. Luschnig. 2005. Regulating the Regulator: The Control of
Auxin Transport. Bioessays27: 1246–55.
Benjamins, R., A. Quint, D. Weijers, P. Hooykaas and R. Offringa. 2001. The PINOID Protein
Kinase Regulates Organ Development in Arabidopsis by Enhancing Polar Auxin Transport.
Devel128: 4057–67.
Bennett, M. J., A. Marchant, H. G. Green, S. T. May, S. P. Ward, P. A. Millner, A. R. Walker, B.
Schulz and K. A. Feldmann. 1996. Arabidopsis Aux1 Gene: A Permease-Like Regulator of Root
Gravitropism. Science273: 948–50.
Bennett, S. R. M., J. Alvarez, G. Bossinger and D. R. Smyth. 1995. Morphogenesis in Pinoid
Mutants of Arabidopsis thaliana.Plant J.8: 505–20.
Bernasconi, P. 1996. Effect of Synthetic and Natural Protein Tyrosine Kinase Inhibitors on Auxin
Efflux in Zucchini (Cucurbita pepo) Hypocotyls. Physiol Plant96: 205–10.
Björkman, T. and R. Cleland. 1991. The Role of Extracellular Free Ca2+Gradients in Gravitropic
Signalling in Maize Roots. Planta 185: 379–84.
Blakeslee, J. J., W. A. Peer and A. S. Murphy. 2005. Auxin Transport. Curr Opin Plant Biol
8: 494–500.
Blancaflor, E. B., J. M. Fasano and S. Gilroy. 1998. Mapping the Functional Roles of Cap Cells in
the Response of ArabidopsisPrimary Roots to Gravity. Plant Physiol116: 213–22.
Blancaflor, E. B. and P. H. Masson. 2003. Plant Gravitropism. Unraveling the Ups and Downs of
a Complex Process. Plant Physiol133: 1677–90.