Scientists have cloned the gene in tomatoes that formsethylene, the fruit-ripening regulator whose enzyme haspreviously proved recalcitrant to purification, according to themost recent edition of the Proceedings of the NationalAcademy of Sciences.

Researchers from the University of Nottingham in England andFrench collaborators at ENSA Toulouse generated a cDNA thatconfers ethylene-forming activity to yeast. The cloned genedirects synthesis of ethylene in transgenic plants.

Previous ideas about the ethylene-forming enzyme have beengained from indirect observations, the researchers said.Expressing the gene for the enzyme in yeast will allowbiochemical analysis of the enzyme and characterization ofproteins it encodes, they wrote.

The British researchers have filed a patent on their method.Several biotech companies are also attempting to slowripening to prolong the shelf life of fruits and vegetables.Monsanto Co. is field-testing tomatoes with a bacterial genethat inhibits production of ethylene. The British process "is analternative strategy to exactly the same end," Monsantoresearcher Harry Klee told BioWorld.

Calgene Inc. last week filed for Food and Drug Administrationpermission to market its antisense tomato, which resistsripening with a gene that reduces breakdown of pectin. --Roberta Friedman, Ph.D.

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