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PLANT HORMONE RECEPTORS

Objective

KNOWLEDGE OF PLANT HORMONES IS ESSENTIAL IN THE MANIPULATION OF PLANT GROWTH, DIFFERENTIATION AND REGENERATION FOR PRACTICAL PURPOSES. THE DEVELOPMENT OF SOPHISTICATED TECHNOLOGIES FOR THE DESIGN AND PRACTICAL USE OF PLANT GROWTH HORMONES, AND FOR THE INDUCTION AND REGULATION OF CELL REGENERATION IN THE TEST TUBE TOWARDS THE DIFFERENTIATED PLANT IN THE FIELD HAVE BEEN HAMPERED BY A LOW LEVEL OF UNDERSTANDING OF THE PERCEPTION AND TRANSDUCTION OF PLANT HORMONES.

THE CURRENT STUDIES ON PLANT HORMONE RECEPTORS INVOLVE A SMALL NUMBER OF GROUPS ALMOST EXCLUSIVELY SITUATED IN WESTERN EUROPE. BY BRINGING THESE GROUPS TOGETHER, THE PROJECT SHOULD SPEED UP SCIENTIFIC AND TECHNICAL PROGRESS IN THE ABOVE AREA. IT SHOULD BE REGARDED AS A DECISIVE CONTRIBUTION TO A DIFFICULT SOLUTION TO THE LACK OF RESPONSIVENESS SHOWN BY MAJOR CROP SPECIES WHEN STIMULATED BY THE RANGE OF KNOWN EFFECTORS IN VITRO.
Deeper insights into the mechanism(s) by which cells detect plant hormones by means of receptor and transduce these primary signals into secondary messenger molecules, can lead to novel methods for the manipulation of growth and development of higher plants. Biochemical, immunological and molecular approaches have been used to purify and characterize receptor proteins for auxin, for fusicoccin (which is a plant hormone related compound produced by the plant pathogenesis fungus Fusicoccum amygdali), and for ethylene. Primary auxin response genes have been isolated in order to identify, either directly, auxin receptor proteins involved in modulating the expression of specific genes.

A protein that binds auxin has been purified and the gene cloned. Antibodies to the protein have been used to show that it acts as a receptor on the outerface of the cell membrane. Transgenic cell systems have been developed to identify auxin receptor forms involved in the modulation of expression of primary auxin responsive genes. A receptor function for a fusicoccin binding protein has been demonstrated by in vitro reconstitution of a proton pumping system which is stimulated by fusicoccin. An ethylene binding protein has been purified to homogeneity and highly specific antibodies directed against the binding protein have been raised. Levels of the binding protein correlate with ethylene sensitivity (eg, ethylene insensitive mutants of Arabidopsis have extremely low levels), thus showing that the binding protein probably acts as a receptor.
THE AIM OF THE PROJECT IS TO IMPROVE TECHNIQUES OF IDENTIFICATION, ISOLATION, CHARACTERIZATION, LOCALIZATION, QUANTITATION AND ANALYSIS OF THE FUNCTION OF PLANT-HORMONE RECEPTORS.
THE FIVE GROUPS WILL CONTRIBUTE TO THE JOINT PROGRAMME THEIR SPECIFIC EXPERTISE ON PARTICULAR RECEPTOR SYSTEMS :

- MEMBRANE-BOUND AND "SOLUBLE" AUXIN-RECEPTOR SYSTEMS (BONN, LEIDEN, EAST MALLING);
- ETHYLENE-RECEPTOR SYSTEMS (ABERYSTWYTH);
- FUSICOCCIN-RECEPTOR SYSTEMS (ROME);
- ENDOGENOUS AUXIN-TRANSPORT INHIBITORS (EAST MALLING, ROME).
UNRAVELLING, IN PARTICULAR, THE RELATIVELY SIMPLE MECHANISM OF ACTION OF FUSICOCCIN, WHICH MIMICKS THE ACTION OF SOME PLANT HORMONES, MIGHT REVEAL A FEW STEPS IN THE MORE COMPLICATED TRANSDUCTION CHAIN OF THE HORMONE.
IT IS EXPECTED THAT TECHNICAL PROBLEMS, SUCH AS APPLICATION OF IMMUNOLOGICAL OR BIOCHEMICAL METHODS, EXPERIMENTS OF FUNCTIONAL RECONSTRUCTION, CAN BE SOLVED THROUGH THE ADDED VALUE GENERATED BY POOLING KNOWLEDGE AND EXPERTISE ACROSS BOUNDARIES.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Rheinische Friedrich-Wilhelms-Universität Bonn
Address
Nußallee 14-16
53115 Bonn
Germany

Participants (4)

East Malling Research Station
United Kingdom
Address
East Malling
ME19 6BJ Maidstone
UNIVERSITA DEGLI STUDI DI ROMA LA SAPIENZA
Italy
University of Leiden
Netherlands
Address

2300 RA Leiden
University of Wales, Aberystwyth
United Kingdom
Address
Old College King Street
SY23 2AX Aberystwyth