Agriculture Reference
In-Depth Information
GGDP
P
P O
O P
P
GGDP
Psy (crtB)
Phytoene
Pds (crtP)
ζ -Carotene
Zds (crtQ)
Lycopene
CrtL-e
CrtL-b
δ-Carotene
γ-Carotene
CrtL-b
CrtL-b
α-Carotene
β-Carotene
CrtR-e
CrtR-b
CrtR-b
OH
OH
Lutein
Zeaxanthin
HO
HO
aba2
OH
O
HO
Violaxanthin
?
OH
OH
Neoxanthin
HO
FIGURE 3.2 Carotenoid. biosynthesis. in. plants.. GGDP,. geranylgeranyl. diphosphate;. Psy,.
phytoene.synthase;.Pds,.phytoene.desaturase;.Zds,.ζ-carotene.desaturase;.CrtL-e,.lycopene.
ε-cyclase;.CrtL-b,.lycopene.β-cyclase;.aba2,.zeaxanthin.epoxidase..(From.Ronen,.G..et.al.,.
Plant J .,.17,.341,.1999..With.permission.)
new  colors.. Indeed,. bright. yellow. and. orange. Lotus . lowers. were. observed. in.
transgenic. plants. transformed. with. the. Agrobacterium aurantiacum . β-carotene.
ketolase. ( crtW ). gene. 29 . The. CrtW. enzyme. accepts. β-carotene,. β-cryptoxanthin,.
and.zeaxanthin.substrates.for.production.of.ketocarotenoids,.which.are.compounds.
found.in.bacteria,.fungi,.algae,.and.only.a.few.plant.species..Transgenic.lotus.plants.
expressing. crtW .had.altered.carotenoid.proiles.with.orange.lines.exhibiting.a.1.5-
fold.increase.in.total.carotenoids.and.ketocarotenoids.making.up.about.one-quarter.of.
the.total.carotenoid.content.
Flower. color. range. can. also. be. extended. through. modiication. of. carotenoid.
breakdown.pathways.(Table.3.1)..Oxidative.breakdown.of.carotenoids.is.catalyzed.
by.a.family.of.carotenoid.cleavage.dioxygenases.(CCDs).found.in.plants,.animals,.
and. bacteria.. The. carotenoid. breakdown. products,. or. apocarotenoids,. are. biologi-
cally. important. molecules. functioning. as. hormones,. lavor. and. fragrance. com-
pounds,.and.defense.molecules.(reviewed.by.Auldridge.et.al. 30 )..There.are.multiple.
lines.of.evidence.that.support.a.role.for.CCDs.in.carotenoid.turnover..Arabidopsis.
ccd1-1 .loss.of.function.mutants.have.increased.seed.carotenoid.content. 31 .Expression.
 
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