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The roles of auxin conjugates in regulating levels of the plant hormone auxin
Bonnie Bartel, Professor
Department of Biochemistry and Cell Biology
bartel@rice.edu
We use Arabidopsis mutants to identify genes providing inputs to the auxin pool, to distinguish precursors from active auxin, and to disentangle contributions of different auxin biosynthetic pathways to development. We have isolated Arabidopsis mutants resistant to auxin storage forms (including the IAA-amino acid conjugates IAA-Ala and IAA-Leu) that remain sensitive to free IAA. 

Two of these mutants, ilr1 and iar3, led to the discovery of enzymes that can release free IAA from conjugates.  In contrast, ilr2, ilr3, and iar1 defects uncovered a role for metal homeostasis in auxin metabolism. 

We currently are working to identify the genes defective in additional conjugate response mutants and using these mutants to elucidate the importance of various auxin storage forms during plant development.



Lab members with conjugate projects:

Collaborator:

Rebekah Rampey

Former Graduate Students:

Haifeng Chen (M.A., 1999)
Jamie Lasswell (Ph.D., 2000)
Sherry LeClere (Ph.D., 2002)
Mónica Magidin (Ph.D., 2002)
Rebekah Rampey (Ph.D., 2004)
Andrew Woodward (Ph.D., 2005)
Luise Rogg (Ph.D., 2001)
Rosie Tellez (1995-2001)


We gratefully acknowledge support for this research from the NIH, the Robert A. Welch Foundation, a NIH Training Grant (T32-GM08362; SL), and Houston Livestock Show and Rodeo Scholarships (RR, SL, JL, RT).

Rebekah Rampey

Publications on conjugates:

Other Bartel lab projects:
Auxin signaling, IBA, peroxisomes

An Arabidopsis basic helix-loop-helix leucine zipper protein modulates metal homeostasis and auxin conjugate responsiveness. 
Rampey, R.A., Woodward, A.W., Hobbs, B.N., Tierney, M.P., Lahner, B., Salt, D.E., and Bartel, B. (2006) Genetics 174, 1841-1857.
Abstract; full text

Auxin: regulation, action, and interaction. 
Woodward, A.W. and Bartel, B. (2005) Annals of Botany,95, 707-735.
Abstract; full text

A family of auxin-conjugate hydrolases that contribute to free indole-3-acetic acid levels during Arabidopsis germination.
Rampey, R.A., LeClere, S., Kowalczyk, M., Ljung, K., Sandberg, G., and Bartel, B. (2004) Plant Physiology 135, 978-988.
Abstract; full text; PDF

IAR4, a gene required for auxin conjugate sensitivity in Arabidopsis, encodes a pyruvate dehydrogenase E1a homolog.
LeClere, S., Rampey, R.A., and Bartel, B. (2004) Plant Physiology 135, 989-999.
Abstract; full text; PDF

ILR2, a novel gene involved in IAA conjugate sensitivity and metal transport in Arabidopsis thaliana.
Magidin, M., Pittman, J.K., Hirschi, K.D., and Bartel, B. (2003) The Plant Journal 35, 523-534.
Abstract; full text; PDF

Characterization of a family of IAA-amino acid conjugate hydrolases from Arabidopsis
LeClere, S., Tellez, R., Rampey, R.A., Matsuda, S.P.T., and Bartel, B. (2002) Journal of Biological Chemistry 277, 20446-20452.
Abstract; full text; PDF

Inputs to the active indole-3-acetic acid pool: de novo synthesis, conjugate hydrolysis, and indole-3-butyric acid b-oxidation.
Bartel, B., LeClere, S., Magidin, M., and Zolman, B.K. (2001) Journal of Plant Growth Regulation 20, 198-216.  (Review Article)
Abstract; full text

Cloning and characterization of IAR1, a gene required for auxin conjugate sensitivity in Arabidopsis.
Lasswell, J., Rogg, L.E., Nelson, D.C., Rongey, C., and Bartel, B. (2000)  Plant Cell 12, 2395-2408. 
Abstract; full text; PDF

IAR3 encodes an auxin conjugate hydrolase from Arabidopsis. 
Davies, R.T., Goetz, D.H., Lasswell, J., Anderson, M.N., and Bartel, B. (1999) Plant Cell 11, 365-376.
Abstract; full text; PDF

Redundancy as a way of life - IAA metabolism.
Normanly, J. and Bartel, B. (1999) Current Opinion in Plant Biology 2, 207-213. (Review Article)
Abstract

ILR1, an amidohydrolase that releases active indole-3-acetic acid from conjugates.
Bartel, B. and Fink, G.R. (1995) Science 268, 1745-1748. 
Abstract


Links:
TAIR (The Arabidopsis Information Resource)
T-DNA Express at the Salk Institute (insertion lines)
American Society of Plant Biologists (Plant Cell, Plant Physiology)
Center for Plant Science at Rice University
Biochemistry and Cell Biology Department

Biochemistry