Agriculture Reference
In-Depth Information
to. insect. pests. and. to. avoid. chemical. pesticide. use.. The. predominant. strategy. to.
engineer. CM. resistance. in. tree. crops. has. been. through. expression. of.
Bacillus
thuringiensis
.(Bt).genes.that.encode.insecticidal.crystal.proteins.(ICP).
166-169
.In.vitro.
studies.have.shown.that.ICPs.bind.with.high.speciicity.and.afinity.to.speciic.cell.
receptors.on.the.insect.brush.border.membrane.of.midgut.epithelial.cells.
170-172
.This.
binding. correlates. with. the. formation. of. pores. and. membrane. lesions. in. the. mid-
gut. that. lead. to. swelling,. leakage,. and. lysis. of. the. epithelium,. ultimately. causing.
death.of.the.insect.through.starvation.and.septicemia.
172-174
.ICP.genes.from.differ-
ent.
Bacillus
. species. are. categorized. according. to. the. host. range. of. their. activity.
and.DNA.sequence.homology.
174,175
.The.
cry
lA(c).protein.was.found.to.be.the.most.
toxic.to.CM.larvae,
176
.but.the.transformation.of.apple
166
.and.walnut
167
.with.
cry1A
(c).
produced.very.low.levels.of.gene.expression..This.was.a.result.of.codon.bias.in.the.
bacterial.gene.sequence,.which.resulted.in.very.low.levels.of.translation.
167,169
.Codon-
optimized.synthetic.versions.of.
cry
IAc.have.been.introduced.into.apple,.where.they.
confer.high.levels.of.mortality.to.CM.larvae.both.under.greenhouse.and.ield.con-
ditions.. Similar. experiments. have. also. been. done. in. walnut
177
. and. persimmon,
178
.
where. chemically. synthesized. versions. of.
cry
IAc. provided. excellent. protection.
against.target.insect.larvae..Transgenic.tissues.expressing.cryIAc.protein.at.as.low.
as.0.02%.of.total.cellular.protein.produced.100%.mortality.in.CM.larvae.
177
.Recent.
studies.have.shown.evidence.that.RNA.silencing.pathways.also.play.a.role.in.plant.
defense.against.insects,.which.can.provide.an.alternative.biotechnological.strategy.
to.develop.pest.control.in.plants.
179
Epiphyas postvittana
(Light Brown Apple Moth)
Epiphyas postvittana
,.the.light.brown.apple.moth,.is.a.native.pest.of.horticultural.
crops. in. Australia. and. New. Zealand,
180
. and. is. now. present. in. New. Caledonia,.
North-Western.Europe,.Hawaii,.and.California..The.larvae.of.the.light.brown.apple.
moth. cause. signiicant. damage. to. apple. foliage. and. fruit.. To. confer. resistance. to.
E. postvittana
,. the. apple. cultivar. 'Royal. Gala'. was. transformed,. incorporating.
genes.encoding.the.potato.(
Solanum tuberosum
).biotin.binding.proteins.avidin.and.
strepavidin.. In. the. absence. of. biotin,. an. essential. vitamin. for. insects,. 80%-90%.
of.larvae.feeding.on.the.transgenic.apple.lines.died.in.a.period.of.3.weeks,.com-
pared. to. 14%.on. the. control. plants.
181
. The.recent. identiication.of.genes. involved.
in.
E. postvittana
. digestion
182
. has. allowed. proof-of-concept. research. focused. on.
the. development. of. an. alternative,. RNAi-based. strategy. to. combat. this. pest.. In.
controlled.feeding.experiments.with.
E. postvittana
.larvae,.oral.delivery.of.dsRNA.
homologous.to.the.
EposCXE1
.led.to.silencing.of.the.native.carboxylesterase.gene.
EposCXE1
,.which.encodes.a.larval.midgut.enzyme.involved.in.digestion.
183
OUTPUT TRAITS
The.genetic.modiication.of.input.traits.enhances.the.agricultural.properties.and.per-
formance.of.a.crop,.with.the.grower.as.the.primary.beneiciary..In.contrast,.trans-
genic.crops.with.altered.output.traits,.such.as.increased.shelf.life,.enhanced.nutritive.
value,.or.reduced.allergenicity,.primarily.beneit.the.consumer..In.perennial.orchard.
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