Molecular Approaches for Transgene Containment and Their Potential Applications in Horticultural Crops - Transgenic Horticultural Crops: Challenges and Opportunities - page 295

wild-type.control.plants.grown.under.identical.conditions,.although.fruit.productivity.
per.plant.was.not.signiicantly.altered.
Seeds.can.be.produced.from.many.naturally.or.transgenically.produced.seedless.
fruit.plants.if.pollination.is.enforced..To.have.a.total.sterility.of.seedless.fruit.plants,.
we.have.also.constructed.a.number.of.gene.cassettes.that.can.lead.to.both.male.and.
female.sterility.and.also.production.of.normal.sized.fruits.with.no.seeds. 67 .We.used.
reproductive.organ-speciic.gene.promoters.to.control.the.expression.of.a.cytotoxin.
gene,. the. bacterial. barnase. gene. for. the. initial. testing,. to. achieve. both. male. and.
female. sterility.. We. used. an. ovary-speciic. gene. promoter. to. control. overproduc-
tion.of.auxin.for.seedless. fruit.production. 68 .With.a. combination. of. the.male-.and.
female-sterility.gene.and.the.seedless.fruit.gene,.we.have.demonstrated.that.trans-
genic.tobacco.and.tomato.plants.are.totally.sterile.(both.male.and.female.sterile).and.
also.capable.of.producing.normal.sized.fruit.with.no.seeds. 67
Nonhormonal. genes. have. also. been. shown. to. be. capable. of. producing. seedless.
fruits..For.example,.Yao.et.al. 73 .have.shown.that.the.loss.of.function.mutation.in.the.
MdPI.MADS-box.transcription.factor,.a.homolog.of. Arabidopsis .mutant.pistillata,.con-
fers.parthenocarpic.fruit.development.in.apple.plants..Ampomah-Dwamena 74 .reported.
that. repression. of. a. tomato. MADS. box. gene,. TM29 ,. using. either. cosuppression. or.
antisense.techniques,.resulted.in.infertile.stamens.and.ovaries.and.subsequently.led.to.
the.production.of.parthenocarpic.fruits..However,.these.transgenic.tomato.plants.also.
produced.aberrant.lowers.with.morphogenetic.alterations.in.the.organs.of.the.inner.
three. whorls.. Ito. and. Meyerowitz 75 . reported. that. overexpression. of. the. cytochrome.
P450 .gene.could.lead.to.production.of.parthenocarpic.fruits..Wild-type. Arabidopsis .
fruits.developed.to.normal.size.only.if.the.ovules.were.fertilized.. When.expression.
of. the. cytochrome. P450 . gene. was. hyperactivated,. fruits. grew. without. fertilization.
and. reached. nearly. normal. size.. When. wild-type. pollen. was. used. to. pollinate. the.
cytochrome.P450.overexpressing.plants,.the.pollinated.fruits.became.more.than.10%.
longer.and.40%.wider.than.wild-type.fruits.but.they.produced.very.few.seeds.
Seedless.fruit.technologies.can.be.used.to.reduce.seed-mediated.transgene.escape.
from.horticultural.crops.if.seeds.of.these.plant.species.are.of.little.value..Since.seeds.
can.be.produced.from.seedless.fruit.plants.if.pollination.is.enforced,.seedless.fruit.
technologies.can.be.used.in.both.vegetatively.and.sexually.propagated.crops..Further,.
the.use.of.a.seedless.fruit.technology.should.lead.to.improvement.of.fruit.quality.and.
productivity. 68,69,76
c hloroplaSt t ranSformatIon
Chloroplasts.of.higher.plants.are.semiautonomous.organelles.with.a.small,.highly.
polyploid. genomes. and. their. own. transcription-translation. machinery. 77 . In. most.
lowering.plants,.chloroplasts.are.inherited.from.their.female.parents.although.for.
some. plant. species. such. as. pines. their. chloroplasts. are. inherited. from. pollen. 78,79 .
For. the. plant. species. whose. chloroplasts. are. inherited. only. from. the. female,. if.
transgenes. are. intergrated. into. the. chloroplast. genome,. pollen. produced. from. the.
resulting.transgenic.plants. should.be. transgene.free..In.the.case.of.tobacco.plants.
with. transgenes. inserted. into. chloroplast. gemone,. for. instance,. only. three. out. of.
1,000,000.pollen.grains.contain.transgenes. 78