15th International Conference on Arabidopsis Research - TAIR

T07-021
Equilibrative nucleoside transporters (ENT) influence
physiology and development in Arabidopsis
Michaela Traub(1), Martin Flörchinger(1), H. Ekkehard Neuhaus(1), Torsten
Möhlmann(1)
1-University of Kaiserslautern
Members of the protein family of equilibrative nucleoside transporters (ENTs)
have been identified in diverse organisms like mammals, protists, and fungi.
Nucleoside transporters are reportedly involved in the salvage pathways
of nucleotide synthesis. We confirmed that nucleoside uptake and salvage
occurs in Arabidopsis leaves and Ricinus cotyledons. The Arabidopsis ENT
family comprises of eight members in total. The heterologous expression in
yeast cells allowed us to characterize the transport properties of AtENT1, 3,
4, 6 and 7 for purine and pyrimidine nucleosides and related compounds.
The subcellular localisation has been revealed by GFP-fusion constructs and
transient expression in tobacco protoplasts. We studied the tissue specificity
of all eight AtENTs applying quantitative RT-PCR and furthermore analysed
the cell type specific expression of some AtENTs by promoter-GUS-fusion.
Moreover, we identified growth conditions that affect the regulation of AtENT
gene expression like pathogen-attack, wounding, senescence and nutrientlimitation.
In addition, knockout plants for several AtENTs display phenotypes
under distinct growth conditions pointing to an involvement of these proteins
in physiology and development in Arabidopsis. Results of the previously listed
experiments will be presented on our poster.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T07-022
Identification of new glucosinolate-biosynthesis
genes induced by coronatine
Markus Piotrowski(1), Andreas Schemenwitz(1), Anna Lopukhina(1), Tim
Janowitz(1), Elmar W. Weiler(1), Claudia Oecking(2)
1-Dep. of Plant Physiology, Ruhr-Universität Bochum
2-Plant Physiology, Center for Plant Molecular Biology Tübingen
The phytotoxin coronatine is a structural analog of the octadecanoid signal
molecules jasmonic acid and 12-oxophytodienoic acid, which are important
for activation of plant defense genes. In order to isolate novel coronatine-regulated
genes from Arabidopsis thaliana, differential mRNA display was performed
(Lopukhina et al., 2001). One of the genes identified by this method,
CORI-7, is annotated as a member of the sulfotransferase family. The cDNA
for CORI-7 was obtained and expressed in Escherichia coli. The purified
protein showed sulfotransferase activity towards several desulfo-glucosinolates
transferring the sulfate group of 3’-phosphoadenosine-5’-phosphosulfate
to the desulfo-glucosinolates and thereby catalyzes the last step in the
biosynthesis of the glucosinolate core structure. Glucosinolates are secondary
compounds found in many species of the Brassicales (Capparales) and are
involved in herbivore- and pathogen-defense reactions in these plants. It is
known for more than ten years that plants treated with jasmonic acid contain
increased amounts of glucosinolates (e.g. Bodnaryk, 1993), and we therefore
suppose that CORI-7 is involved in the biosynthesis of glucosinolates in vivo.
The regulation of the CORI-7 gene by several herbivore- or pathogen-defense
signaling compounds and the impact of coronatine on glucosinolate biosynthesis
in comparison to jasmonic acid was studied.
Interestingly, other genes found to be up-regulated by coronatine in this
screen, like a C-S lyase and a methyltransferase, do, in principle, also catalyze
reactions taking place during the biosynthesis of glucosinolates and may
therefore also be involved in this pathway.
Bodnarik (1993) Phytochemistry 35:301-305
Lopukhina et al. (2001) Plant Phys. 126:1678-1687
T07 Metabolism (Primary, Secondary, Cross-Talk and Short Distance Metabolite Transport)