Sensitivity to ethylene increases as flowers
mature, and this is associated with autocatalytic ethylene
production that initiates petal senescence. The coordination
of the senescence process within the flower requires
interorgan communication. To determine if differential
ethylene responsiveness among floral organs is involved
in regulating senescence signaling, ethylene biosynthesis
and the expression of ethylene biosynthetic genes were
investigated in styles, ovaries, and petals from 6 stages
of flowers following ethylene treatment. As flowers matured,
all floral organs investigated became more responsive
to ethylene. Ovaries were the first flower organ that
had detectable increases in ethylene production following
ethylene treatment. In stage 4 and 5 flowers, the
highest levels of ethylene production were detected in
petals, while styles had the highest ethylene production
at stage 6. 1-Aminocyclopropane-1-carboxylic acid (ACC)
synthase (ACS) and ACC oxidase (ACO) genes were induced
by ethylene treatment, and transcript abundance of
DCACS1, DCACS2 and DCACO1 increased in all floral
organs as flowers matured. DCACS3, a pollinationresponsive
ACS gene, did not show a significant increase
in transcript levels following ethylene treatment
except in styles. Patterns of gene expression in ethylenetreated
styles and petals corresponded with increases in
ethylene biosynthesis, with increases in ACS mRNA
abundance detected at stage 1 or 2 in petals and at stages
4, 5, or 6 in styles. The largest increases in ethylene production
and gene expression occurred in styles at stages
5 and 6 and corresponded to the stages at which the
styles were first receptive to pollination. Reasons for differential
ethylene sensitivity among the flower organs
during development are discussed
Sensitivity to ethylene increases as flowersmature, and this is associated with autocatalytic ethyleneproduction that initiates petal senescence. The coordinationof the senescence process within the flower requiresinterorgan communication. To determine if differentialethylene responsiveness among floral organs is involvedin regulating senescence signaling, ethylene biosynthesisand the expression of ethylene biosynthetic genes wereinvestigated in styles, ovaries, and petals from 6 stagesof flowers following ethylene treatment. As flowers matured,all floral organs investigated became more responsiveto ethylene. Ovaries were the first flower organ thathad detectable increases in ethylene production followingethylene treatment. In stage 4 and 5 flowers, thehighest levels of ethylene production were detected inpetals, while styles had the highest ethylene productionat stage 6. 1-Aminocyclopropane-1-carboxylic acid (ACC)synthase (ACS) and ACC oxidase (ACO) genes were inducedby ethylene treatment, and transcript abundance ofDCACS1, DCACS2 and DCACO1 increased in all floralorgans as flowers matured. DCACS3, a pollinationresponsiveACS gene, did not show a significant increasein transcript levels following ethylene treatmentexcept in styles. Patterns of gene expression in ethylenetreatedstyles and petals corresponded with increases inethylene biosynthesis, with increases in ACS mRNAabundance detected at stage 1 or 2 in petals and at stages4, 5, or 6 in styles. The largest increases in ethylene productionand gene expression occurred in styles at stages5 and 6 and corresponded to the stages at which thestyles were first receptive to pollination. Reasons for differentialethylene sensitivity among the flower organsduring development are discussed
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