Agriculture Reference
In-Depth Information
However,. when. needed,. seed. germination. and. seedling. growth. can. be. restored.
through.a.heat.shock.treatment.of.germinating.seeds..Thus,.the.RBF.system.could.
be.a.useful.tool.to.reduce.seed-mediated.escape.of.transgenes.
As.represented.by.the.“terminator”.seed.and.RBF.systems,.genesafe.technologies.
are.conditional.seed.sterility.technologies..For.the.“terminator”.seed.technology,.one.
important.requirement.is.high.eficiencies.of.the.chemical-induced. removal.of.the.
blocking.DNA.sequence.from.the.barnase.gene..On.the.other.hand,.high.eficiency.
of. the. barstar. gene. in. the. RBF. system. is. not. critical.. Regarding. the. food. safety.
concerns,.it.should.be.noted.that.the.barnase.gene.used.in.the.two.genesafe.systems.
discussed.in.“Male.and.female.sterility”.section.may.be.replaced.with.a.gene.whose.
product.is.nontoxic.to.humans.or.animals.
p
arthenocarpy
t
echnoloGy
Parthenocarpy.(seedlessness).is.the.production.of.normal-sized.fruits.without.fertil-
ization.and.the.fruit.produced.contains.no.embryo.and.endosperm..Fruit.development.
in.higher.plants.normally. requires.pollination,.fertilization,.and.seed.development.
that.stimulate.cell.division.of.speciic.loral.and.fruit.tissues..Traditionally,.parthe-
nocarpic. fruits. are. produced. from. mutants,. triploid. plants,.or.lowers. treated. with.
exogenous. growth. regulators.
62
. Transgenic. parthenocarpy. was. reported. in. auxin-
overproducing. transgenic. petunia
63
. and. in. tobacco. plants
64
. using. the.
iaaM
. gene.
cloned. from.
Agrobacterium tumefaciens
.
63
. With. ovary-. or. fruit-speciic. gene. pro-
moters. to. direct. expression. of. the.
iaaM
. gene. or.
RolB
. gene,. seedless. fruits. were.
produced.from.eggplant,.tobacco,.tomato,.and.watermelon.
65-69
Rotino
69
.reported.that.transgenic.tobacco.and.eggplants.that.expressed.the.coding.
region.of.the.
iaaM
.gene.from.
Pseudomonas syringae
pv
. savastanoi
,.driven.by.an.
ovule-speciic.
DefH9
.gene.promoter.from.
Antirrhinum majus
,.produced.partheno-
carpic.fruits..If.lowers.were.emasculated,.seedless.fruits.were.produced.from.these.
transgenic.plants..If.pollinated,.the.plants.produced.fruits.containing.seeds..In.the.
case.of.eggplant,.the.expression.of.the.
iaaM
.transgene.enabled.fruit.set.and.growth.
under. environmental. conditions. where. no. fruit. setting. was. observed. in. the. wild-
type.control.plants..Under.normal.growth.conditions,.the.transgenic.plants.produced.
marketable.fruits.from.pollinated.or.unpollinated.transgenic.lowers,.but.the.control.
plants.produced.fruits.of.marketable.size.only.if.lowers.were.fertilized.
69
We. have. used. two. types. of. gene. promoters. to. control. the. expression. of. the.
Agrobacterium iaaM
.gene..One.is.the.auxin.inducible,.ovary.active.
GH3
.promoter.
cloned.from.soybean
70,71
.and.another.is.the.ovary.speciic.
AGL5
.promoter.
72
.Using.
these.two.
iaaM
.fusion.genes,.we.produced.transgenic.
Arabidopsis
,.tobacco,.tomato,.
and.watermelon.plants.
68
.Transgenic.plants.that.expressed.the.
GH3
.promoter::
iaaM
.
or.
AGL5
. promoter-
iaaM
. gene. were. capable. of. producing. seedless. fruits.. Also,.
because.overproduction.of.auxin.in.the.transgenic.plants.was.restricted.to.the.ovary.
and.developing.fruit,.no.obvious.side.effects.were.evident..The.seedless.tomato.and.
watermelon. fruits. produced. from. the. transgenic. plants.contained. similar. levels. of.
acids.and.sugars,.vitamins,.and.other.nutrients.relative.to.the.seeded.fruits.produced.
from.control.plants..Furthermore,.the.seedless.tomatoes.and.watermelons.were.nor-
mal. in. size. or. sometimes. were. signiicantly. larger. than. those. produced. from. the.
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