celenza@bu.edu

Cell Signalling and Gene Regulation Genetics Developmental Biology

Associate Professor of Biology
Ph.D., Columbia University, 1988

Plant development, molecular biology, genetics

Lateral root formation is the primary way in which plants enlarge their root system and requires the coordination of many developmental processes including cell division, cell expansion and differentiation. Lateral roots arise from a subset of pericycle cells which then differentiate into a mature lateral root containing the same tissues found in the primary root. The plant growth hormone, indole-3-acetic acid (IAA), induces lateral root formation in a dose dependent manner and is thought to be an in vivo regulator of lateral root formation. In addition, the root system is greatly influenced by the local environment and by genetic regulation.

The major goal of my laboratory is to understand how the plant growth hormone, indole-3-acetic acid (IAA), regulates lateral root formation in the higher plant Arabidopsis thaliana. To achieve this goal we are using two approaches that exploit the amenability of Arabidopsis to classical and molecular genetic techniques.

Identification of Arabidopsis mutants that perturb lateral root formation.

We have isolated and characterized Arabidopsis mutants that exhibit aberrant lateral root formation (alf). The alf1-1 mutation, an allele of rooty and sur1, causes hyperproliferation of lateral roots and adventitious roots because it overproduces IAA. The alf4-1 mutation blocks initiation of lateral roots and is resistant to the IAA induction of cell division. The alf3-1 mutant is defective in the maturation of lateral roots. Lateral roots initiate in the alf3-1 mutant, but then arrest and die. Our recent efforts have been focused on walking to the ALF4 and ALF3 genes which are both located on chromosome 5. Identification of these two genes and characterization of their predicted proteins will allow for the determination of their functions in lateral root development.

Identification of genes involved in IAA metabolism.

Because of the central role of IAA in root system development we have looked for genes involved in IAA biosynthesis. Using a heterologous expression screen, we identified two Arabidopsis genes which encode the cytochrome P450s, CYP79B2 and CYP79B3. These two proteins, when expressed in E. coli convert tryptophan to indole-3-acetaldoxime. Indole-3-acetaldoxime has been proposed as an intermediate in Trp-dependent IAA biosynthesis and is also an intermediate for the biosynthesis of indole glucosinolates, a class of plant defense compounds. We are currently using reverse genetic methods to determine the function of these genes in plants in order to determine the overall importance of these genes for IAA biosynthesis.

Ljung, K., A. K. Hull, J. Celenza, M. Yamada, M. Estelle, J. Normanly, and G. Sandberg (2005). Sites and regulation of auxin biosynthesis in Arabidopsis roots. Plant Cell 17:1090-1104.

Celenza, J.L., J.A. Quiel, G.A. Smolen, H. Merrikh, A. Silvestro, J. Normanly and J. Bender (2005). The Arabidopsis ATR1 Myb transcription factor controls indolic glucosinolate homeostasis. Plant Physiol. 137:253-262.

DiDonato, R. J., E. Arbuckle, S. Buker, J. Sheets, J. Tobar, R. Totong, P. Grisafi, G. R. Fink and J. L. Celenza. 2003.  Arabidopsis ALF4 encodes a nuclear-localized protein required for lateral root formation. The Plant Journal. On-line publication December 11, 2003.

Zhao, Y., A. K. Hull, N. R. Gupta, K. Goss, J. Normanly, J. Chory and J.L. Celenza. 2002. Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3. Genes Dev. 16: 3100-3112.

Ljung K, A. K. Hull, M. Kowalczyk, A. Marchant, J. Celenza, J.D. Cohen and G. Sandberg. 2002. Biosynthesis, conjugation, catabolism and homeostasis of indole-3-acetic acid in Arabidopsis thaliana Plant Mol. Biol. 49: 249-272.

Celenza, J. L. 2001. Natural products derived from the N-hydroxylation of tyrosine and tryptophan. Curr. Opin. Plant Biol. 4: 234-240.

Hull, A. K., Vij, R., and Celenza, J. L. 2000. Arabidopsis cytochrome P450s that catalyze the first step of tryptophan-dependent indole-3-acetic acid biosynthesis. Proc. Natl. Acad. Sci. USA 97, 2379-2384.

Hull, A. K., and Celenza, J. L. 2000. Bacterial expression and purification of the Arabidopsis NADPH-cytochrome P450 reductase ATR2. Protein Expr. Purif. 18, 310-315.

Celenza, J.L., P. Grisafi, and G.R. Fink. 1995. A pathway for lateral root formation in Arabidopsis thaliana. Genes Development 9:2131-2142.

Questions and comments are always welcome.
Copyright © 1996, The Trustees of Boston University
This document was last modified on November 18, 2005.