DELAYED RIPENING TOMATO PLANTS EXPRESSING THE ENZYME 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID DEAMINASE .1. MOLECULAR CHARACTERIZATION, ENZYMEEXPRESSION, AND FRUIT RIPENING TRAITS

Tomato plants that are delayed in fruit ripening have been developed b y Agrobacterium tumefaciens-mediated transfer of a gene encoding 1-ami nocyclopropane-1-carboxylic acid deaminase (ACCd) into the tomato geno me. Two delayed ripening (DR) tomato lines are characterized in this p aper. Line 8338, transformed by a double border plasmid vector, contai ns a single copy of the accd gene, and DNA outside the plasmid border sequences was not transferred to the plant genome. Line 5673, transfor med by a single border plasmid vector, contains a single, complete cop y of the accd gene plus tandem, incomplete copies of the gene. The mea n expression levels of ACCd in fruit collected from four field trials were 39.4 and 20.6 mu g/g of fresh weight for lines 8338 and 5673, res pectively. Fruit ethylene synthesis was significantly reduced, and tim e for fruit to ripen was extended for both DR tomato lines relative to the parental control line. Introduction of the accd gene and the dela yed ripening trait into appropriate tomato varieties will potentially allow production of tomato fruit with superior taste quality.