Transgenic Fruit and Nut Tree Crops Review - Transgenic Horticultural Crops: Challenges and Opportunities - page 17

(b)

(a)

(c)

(d)

(e)

FIGURE 1.1 (See color insert.) . Delayed. fruit. ripening. in. transgenic. apples.. (a). An.
apple.tree.expressing.an.antisense.ACC.oxidase.(ACO).transgene..Ethylene.production.is.
reduced.>90%.in.this.transgenic.line.compared.to.wild-type.controls..(b, c).ACO-silenced.
(b) and.wild-type.(c).apples.stored.at.room.temperature.for.1.month..(d, e).ACO-silenced.
(d). and. wild-type. (e). apples. stored. at. room. temperature. for. 3. months.. (Reprinted. with.
kind.permission.from.Springer.Science+Business.Media:. Transgenic Res .,.Effect.of.down-
regulation.of.ethylene.biosynthesis.on. fruit.lavor.complex. in.apple. fruit,. 13,.2004,. 373,.
Dandekar,.A..M..et.al.)

whether.the.fruit.from.these.plants.would.accumulate.these.compounds.at.levels.that.
could.potentially.beneit.human.health. 142,192 .Preliminary.reports.have.also.described.
attempts. to. increase. vitamin. A. content. in. grapefruit. (through. expression. of. the.
.carotenoid.biosynthetic.genes.phytoene.synthase,..phytoene.desaturase,.and.lycopene.
β-cyclase).and.attempts.to.increase.the.content.of.“heart.healthy”.oleic.acid.in.palm.
oil.(through.expression.of.the.fatty.acid.modifying.genes.β-ketoacyl-ACP.synthase II,.
Δ9-stearoyl-ACP-desaturase,. and. palmitoyl-ACP-thioesterase. [antisense]). 193,194 .
However,.no.phenotypic.characterization.of.the.transgenic.grapefruit.and.oil.palm.
plants.has.yet.been.reported.
A.unique.balance.of.soluble.sugars,.starch,.acids,.and.volatiles.underlies.the.lavor.
and.quality.of.each.type.of.fruit..The.recent.work.of.Teo.et.al..has.demonstrated.that.
fruit.quality/lavor.can.be.dramatically.altered.using.transgenic.approaches. 195 .Unlike.
most. plant. species,. apples. accumulate. and. transport. photosynthate. largely. in. the.
form.of.the.sugar.alcohol.sorbitol,.rather.than.sucrose..Sorbitol.is.synthesized.from.
glucose-6-phosphate. through. the. action. of. the. enzyme. sorbitol-6-phosphate. dehy-
drogenase.(S6PDH),.and.Teo.et.al..generated.transgenic.apple.plants.expressing.an.
antisense.copy.of.the.S6PDH.gene. 195 .Leaves.from.several.resultant.transgenic.lines.