Calgene Inc. has received its first notice of allowance for U.S.patent claims related to control of the fruit-ripening hormoneethylene.

Control of ethylene is expected to have significant commercialvalue in such fresh produce as tomatoes, berries, melons,bananas and tree fruits.

Calgene subsidiary Calgene Fresh has begun field-testingtomatoes that incorporate the ripening-control technologyalong with the previously developed Flavr Savr gene, whichslows softening.

"It's a way of extending shelf life," said John Bedbrook,executive vice president and director of science at DNA PlantTechnology Corp. of Cinnaminson, N.J. "It's very interestingscientifically and will have commercial potential."

An advantage of the technology is that it can be used to reducethe amount of ethylene produced in most plant species.However, this is accomplished by use of a gene from a soilbacterium, which may warrant the same "food additive"regulatory review required of the kanamycin marker geneused in Flavr Savr.

The bacterial gene, 1-aminocyclopropane-1-carboxylic aciddeaminase (ACCD), removes a key substrate in the ethylenebiosynthetic pathway, 1-aminocyclopropane-1-carboxylic acid(ACC).

The ability to control ripening means that growers have morecontrol over when fruit is harvested, said Stephen Benoit, vicepresident of Calgene Fresh. The rate at which ACCD slowsripening varies with plant variety.

Once the fruit is harvested, it remains in the same state ofripeness longer. Ethylene gas is used to prepare the fruit formarket, Bedbrook said. The sugar and acid balance developseven without ethylene, which primarily turns tomatoes red.When unmodified fruit is left on the vine, ethylene alsonaturally leads to fully ripened fruit falling to the ground.

Calgene (NASDAQ:CGNE) of Davis, Calif., will receive patentprotection for its claims to DNA constructs for expression ofACCD in plant cells. The company already has an issued patentcovering the use of antisense RNA techniques to control geneexpression in all plant cells.

-- Nancy Garcia Associate Editor

(c) 1997 American Health Consultants. All rights reserved.