Agriculture Reference
In-Depth Information
transgenes.from.pollen.and/or.seed.of.transgenic.tobacco.plants.
105
.Based.on.analysis.of.
more.than.25,000.progeny.for.each.representative.transgenic.event,.eficiencies.for.
automatic. deletion. of. all. transgenes. from. pollen. and/or. seed. are. as. high. as. 100%.
under. greenhouse. conditions.. Also,. we. have. demonstrated. that. the. high. excision.
eficiency.trait.remained.stable.in.vegetatively.propagated.progeny.plants..The.cur-
rent.version.of.the.gene.deletor.technology.is.readily.applicable.to.address.the.pollen-.
and. seed-mediated. transgene. low. problems. of. vegetatively. propagated. plants. that.
are.important.to.the.agricultural,.forestry,.bioenergy,.ornamental,.and.paper/pulping.
industries..This.technology.can.also.be.used.directly.in.sexually.propagated.crops.if.
artiicial.seeds.(i.e.,.no.pollination.or.fertilization.is.needed).are.used.for.the.propa-
gation.of.these.crops..Artiicial.seeds.have.been.produced.from.many.major.agricul-
tural.crops.
122
A.modiied.version.of.the.current.gene.deletor.technology.could.be.used.in.sexu-
ally.propagated.horticultural.crops.such.as.tomato,.lettuce,.eggplants,.etc..One.pos-
sible.strategy.is.to.introduce.a.chemically.inducible.
RNAi-FLP
.gene.cassette.into.the.
gene. deletor. system.. Application. of.a. chemical. inducer. at. the. correct. time. would.
prevent.the.deletion.of.transgenes.in.pollen.and.seeds..For.instance,.the.ethanol.induc-
ible.
ALCR/alcA
.(alc).two-component.system
123
.could.be.used.to.control.
RNAi-FLP
.
gene. expression.. With. the.
ALCR/alcA (alc)
. system,. application. of. ethanol. during.
pollen/seed. development. would. activate. the.
RNAi-FLP
. gene..
RNAi-FLP
.represses.
the.pollen/seed-speciic.expression.of.FLP.recombinase..As.a.result,.all.transgenes.
will.remain.in.the.pollen.or.seeds.during.that.generation..However,.if.the.inducer.
is.not.applied.in.a.subsequent.generation,.FLP.will.be.expressed..Consequently,.FLP.
expression.will.lead.to.deletion.of.all.functional.transgenes.in.pollen.and.seeds.
The.gene.deletor.technology.may.be.extended.to.generate.non-transgenic.edible.
parts. from. transgenic. plants. to. mitigate. consumer. concerns. over. the. presence. of.
transgenes. in. food. products.. For. instance,. in. the. case. of. the. transgenic. process-
ing.tomatoes.grown.in.California,.the.inal.products,.tomato.paste,.ended.up.being.
exported. to. many. countries. around. the. world.
2
. Approvals. prior. to. exporting. the.
tomato.paste.to.these.countries.had.to.be.obtained.from.each.of.these.countries..If.
the. processed. product. contains. viable. seeds,. environmental. studies. and. approvals.
are.then.required.in.the.importing.country,.even.if.the.importation.is.intended.only.
for.food.consumption..A.fruit-speciic.gene.deletor.system.to.eliminate.all.transgenes.
from.fruit.tissues.might.help.to.simplify.some.of.these.procedures.and.thus.reduce.
associated.costs..With.desirable.organ-.and.tissue-speciic.gene.promoters.or.devel-
opmental.stage.speciically.or.conditionally.inducible.gene.promoters.to.control.the.
FLP
.gene.expression,.it.is.possible.to.obtain.non-transgenic.organs.from.transgenic.
plants.or.to.revert.the.transgenic.plants.back.to.“non-transgenic”.plants.when.needed.
Volunteer. crops. are. plants. growing. from. seeds. that. are. left. in. the. ield. from. a.
previous. planting.. Volunteer. transgenic. plants. are. a. source. of. perceived. or. actual.
environmental.risks.and.have.resulted.in.lawsuits.from.neighboring.farms.or.seed.
companies.. Because. the. gene. deletor. technology. can. remove. all. functional. trans-
genes. from. pollen. and. seeds,. volunteer. plants. in. subsequent. seasons. will. then. be.
non-transgenic.
Deleting.all.transgenes.from.pollen,.seeds.or.other.organs.once.their.functions.are.
completed.probably.is.one.of.the.best.transgene.containment.concepts,.but.eficiency.
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