Transgenic Ornamental Crops - Transgenic Horticultural Crops: Challenges and Opportunities - page 65

useful,. (2). substrate. availability. needs. to. be. considered. when. altering. volatile.
pathways,.and.(3).endogenous.activities.can.convert.products.to.nonvolatile.forms..
The.opportunities.for.signiicant.increases.in.loral.volatile.production.most.likely.lie.
with.controlled.expression.of.genes.early.in.the.biosynthetic.pathways.and.regulatory.
factors.controlling.gene.expression.of.several.biosynthetic.pathways.
Fragrance and Color
Fragrance.benzenoids.and.anthocyanin.color.metabolites.are.produced.from.phen-
ylpropanoid.metabolism..Therefore,.altering.fragrance.metabolism.could.inluence.
the. production. of. color. and. vice. versa.. While. there. are. no. consistent. trends. for.
direct. relationships. between. color. and. fragrance,. there. is. evidence. that. this. does.
occur. in. carnation.. White. lowers. from. antisense. F3H. carnation. plants. produced.
higher.amounts.of.benzenoids.compared.to.the.red-orange.control.lowers. 58 .These.
transgenic.lowers.produced.ive-.to.sevenfold.higher.levels.of.methyl.benzoate.and.
2-hydroxy. methyl. benzoate.. Thus,. in. carnation,. loss. of. F3H. function. may. reduce.
lux.through.anthocyanin.synthesis.causing.phenylpropanoid.metabolism.to.be.redi-
rected.toward.benzenoid.production.
Interplay.between.color.and.fragrance.production.is.less.clear.in.petunia..Vivid.
pink.color.was.introduced.into.a.white.lowered,.nocturnally.fragrant. Petunia axil-
laris . background. by. transformation. with. the. AN2. lavonoid. biosynthesis. regula-
tor. 59 .The.transgenic.colored.lowers.did.not.exhibit.signiicant.changes.in.benzenoid.
volatile.production..Likewise,.colored.petunias.with.reduced.expression.of. ODO1 ,.a.
transcription.factor.thought.to.control.substrate.lux.to.benzenoid.fragrance.produc-
tion. in. petunia,. did. not. exhibit. any. visible. differences. in. pigmentation. compared.
to.controls. 47 .Recently,.Ben.Zvi.et.al. 60 .showed.that.heterologous.expression.of.the.
Arabidopsis thaliana PAP1 . Myb. transcription. factor. in. Petunia hybrida . cultivar.
'Blue. Spark'. led. to. increased. lower. pigmentation. and. increased. levels. of. certain.
fragrance. volatiles.. There. were. three. to. ive. times. more. benzaldehyde. and. higher.
internal. pools. of. phenylacetaldehyde,. benzyaldehyde. 4-hydroxy,. benzaldehyde.
3,4-dimethoxy,.and.vanillin. 60 .The.mechanism.of.how.PAP1.is.regulating.these.two.
processes.in.the.'Blue.Spark'.petunias.remains.to.be.elucidated.
v olatIleS and I nSect p lant d efenSe
Plants.produce.a.myriad.of.volatiles.in.response.to.herbivores.that.serve.to.intoxicate,.
attract. predators. and. parasitoids,. and/or. elicit. an. avoidance. response. in. the. insect.
inlicting.damage.to.the.plant..There.are.only.a.handful.of.documented.examples.of.
engineering.of.plant.defense-related.volatiles..However,.as.this.will.likely.be.a.useful.
method.in.the.future.for.improving.plant.defense.in.both.agronomic.and.ornamental.
crops,. a. few.examples. in.model. systems. will.be.highlighted.here..Increased.para-
sitoid.attraction.and.increased.pest.repellant.properties.have.been.achieved.through.
introducing.single.genes.into.Arabidopsis..For.example,.increased.aphid.parasitoid.
attraction.and.aphid.repellant.behavior.was.induced.in.Arabidopsis.plants.expressing.
(E)-β-farnesene.(Eβf).synthase.cloned.from. Mentha .x. piperita . 61 .The.Eβf.express-
ing.plants.emitted.high.levels.of.Eβf,.an.aphid.alarm.pheromone..Arabidopsis.plants.
overexpressing. a. strawberry. linalool/nerolidol. synthase. ( FaNES1) . gene. produced.