GeneticEngineering of Cold-Tolerant Tomato GlycinebetaineBiosynthesis

susceptible to chilling stress. Exposure to ternperatures below 10°C causes various symptoms of injury, and greatly decreases imit set (i,e., the number of fruits per plants) in most cultivars. Conventional breeding efforts haye failed to produce cultivars with satisfactory cold tolerance, Therefore, we have transforrned tomato (cv. Moneymaker) with the codA gene of Arthrobacter globij?]rmis, which encodes choline oxidase to catalyze the conversion of choline to GB. These transgenic plants express the codA gene and synthesize choline oxidase, while accumulating up to O,23.amol of GB per gram fresh weight in their leaves. During various phases of growth and development, from seed germination to ffuit production, the GB-accumulating plants are more tolerant of chMing stress than their wild-type counterpdits. Moreover, at the reproductive stage, our transgenic tomato plants yield, on average, 3096 more fniit after an episode of chilling stress. We demonstrate here that introducing the biosynthetic pathway of GB into tomato via metabolic engineering is an effective strategy foF improving fruit production under cold-stress