15th International Conference on Arabidopsis Research - TAIR

T02-043
Analysis of the distribution of Arabidopsis thaliana
amidase1, an enzyme capable of forming indole-3acetic
acid from indole-3-acetamide.
Tina Schäfer(1), Elmar W. Weiler(1), Stephan Pollmann(1)
1-Lehrstuhl für Pflanzenphysiologie, Ruhr-Universität Bochum, Universitätsstrasse 150, D-44801
Bochum, Germany
The biosynthesis of the major plant growth hormone indole-3-acetic acid
(IAA) has not yet been fully uncovered. The only clarified pathway of IAA
synthesis which has formerly been known to exclusively exist in phytopathological
bacteria, e.g. in the genera Agrobacterium, leads from tryptophan to
IAA via indole-3-acetamide (IAM). This reaction sequence is catalyzed by a
tryptophan-2-monooxygenase (TMO) and an indole-3-acetamide hydrolase
(IAH). As IAM could be elucidated as an endogenous compound of Arabidopsis
thaliana seedlings (Pollmann et al., 2002), this pathway might also
be valid in this model plant. With IAM as a precursor of IAA and the finding
of a specific IAM hydrolase (AMI1), catalyzing the conversion of IAM to IAA
(Pollmann et al., 2003), the function, distribution and histological localization
of this enzyme has become matter of particular interest.
For this reason the A. thaliana amidase1 was fused to the green fluorescent
protein (GFP) of the jellyfish Aequorea victoria and its subcellular localization
was monitored utilizing transiently transformed plant cells and confocal laser
scanning microscopy.
To further investigate the expression pattern of AMI1 in whole plants we
performed semiquantitative RT-PCR using different plant tissues. In addition,
transgenic Arabidopsis lines carrying the ami1-promoter sequence fused to
the b-glucuronidase (GUS) reporter gene were created. Here we present the
first experiments, pointing out the expression of AMI1 in meristematic tissue
in planta, thus emphasizing the putative AMI1 function in auxin biosynthesis.
Pollmann et al. (2003) Phytochemistry 62, 293-300
Pollmann et al. (2002) Planta 216, 155-161
T02 Development 2 (Shoot, Root)
T02-044
Altered Cytokinin Sensitivity 1 (AtACS1) encodes
a cytokinin-binding protein involved in cytokinin
perception
Christopher G. Wilkins(1), David E. Hanke(1), Beverley J. Glover(1)
1-Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA,
UK
In the 50 years since cytokinins were first characterised as promoters of cell
division they have been shown to influence almost every plant developmental
process. The use of biochemical techniques to identify cytokinin receptors
is an important development in our understanding of this essential group of
plant growth regulators, given the deficiency of mutants with lesions in cytokinin
perception machinery. AtACS1 has been identified as a thaumatin-like
cytokinin-binding protein in Arabidopsis and disruption of AtACS1 expression
alters plant perception of cytokinin.
Analysis of mutant and misexpressing lines has been used to show that
AtACS1 expression is important for normal responses to applied cytokinin.
A T-DNA insertion in the 3'UTR of AtACS1 (Atacs1-1) is sufficient to perturb
root and leaf callus responses, root elongation on exogenous cytokinin and
nutrient stress responses. The location of AtACS1 has been demonstrated to
be extracellular and this cumulative evidence indicates that AtACS1 is a novel
cytokinin receptor.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin