Samenvatting Plant physiology H3: Gibberellins
Plant hormones introduction:
Hormone =
o Signal molecule
o Can be transported
o Regulates developmental processes in small concentrations
In the rest of the course every chapter is for one hormone
Specific
Cross-talk Multiple hormones can be needed for the same fct
This can than also go together with enverinmental factors like light
GA
introduction: Main bioactive GA’s
Discovered in fungus on rice ( all plant hormones can also prod by micro-
org)
Promotes stem elongation
GA bio-assay = Test for presence & activity of GA in (parts of) the plant
o Sensitivity promotion leaf development in dwarf rice by ultra low conc of
GA3 so HIGH activity
o Dose response Estimate GA content based on
plant height
GA Biosynthesis:
Terpenoid synthesis starts with isopentenyl diphosphate &
delivers building blocks, also for other hormones
Precursor GA = geranylgeranyl diphosphate
4 classes of enzymes regulate synthesis to GA12
o CPS = ent-copalyl diphosphate synthase has ga1 mutant (this means that
the ga1 mutant a mutation has in the CPS-gene which leads to less or no
production of the enzyme CPS no elongation slide 19)
o KS = ent-kaurene synthase has ga2 mutant
o KO = ent-kaurene oxidase = CYP450 monooxygenase has ga3 mutant & is
C19
o KAO = ent-kaurenoic acid oxidase = CYP88A monooxygenase is C7
, CYP = cytochrome prot ER localized
Monooxygenase reaction Insertion 1 atom of oxygen in aliphatic position of
STAGE 1 organic substrate, other atom reduced to water with NADPH STAGE 2
STAGE 3
Different
bioactive GA’s
EMS mutagenesis techniek om random mutatie te induceren door ethyl
methanesulfonate toe te dienen
o This is forward genetics = phenotype gene
o Reverse genetics = gene phenotype
GA12 different bioactive GA’s (GA1, GA3, GA4, GA7) has 2 pathways
o C13-hydroxylated pathway Via 13ox, after that 20ox and then 3ox
o Non C13-hydroxylated pathway Same but no use of 13ox but directly 20ox
Compartmentalization
o Stage 1 chloroplast
o Stage 2 chloroplast envelope & ER
o Stage 3 Cytosol
GA inactivation (3 pathways)
o GA2-oxidase
o GA methyltransferase
o CYP714D1
Feedback
Plant hormones introduction:
Hormone =
o Signal molecule
o Can be transported
o Regulates developmental processes in small concentrations
In the rest of the course every chapter is for one hormone
Specific
Cross-talk Multiple hormones can be needed for the same fct
This can than also go together with enverinmental factors like light
GA
introduction: Main bioactive GA’s
Discovered in fungus on rice ( all plant hormones can also prod by micro-
org)
Promotes stem elongation
GA bio-assay = Test for presence & activity of GA in (parts of) the plant
o Sensitivity promotion leaf development in dwarf rice by ultra low conc of
GA3 so HIGH activity
o Dose response Estimate GA content based on
plant height
GA Biosynthesis:
Terpenoid synthesis starts with isopentenyl diphosphate &
delivers building blocks, also for other hormones
Precursor GA = geranylgeranyl diphosphate
4 classes of enzymes regulate synthesis to GA12
o CPS = ent-copalyl diphosphate synthase has ga1 mutant (this means that
the ga1 mutant a mutation has in the CPS-gene which leads to less or no
production of the enzyme CPS no elongation slide 19)
o KS = ent-kaurene synthase has ga2 mutant
o KO = ent-kaurene oxidase = CYP450 monooxygenase has ga3 mutant & is
C19
o KAO = ent-kaurenoic acid oxidase = CYP88A monooxygenase is C7
, CYP = cytochrome prot ER localized
Monooxygenase reaction Insertion 1 atom of oxygen in aliphatic position of
STAGE 1 organic substrate, other atom reduced to water with NADPH STAGE 2
STAGE 3
Different
bioactive GA’s
EMS mutagenesis techniek om random mutatie te induceren door ethyl
methanesulfonate toe te dienen
o This is forward genetics = phenotype gene
o Reverse genetics = gene phenotype
GA12 different bioactive GA’s (GA1, GA3, GA4, GA7) has 2 pathways
o C13-hydroxylated pathway Via 13ox, after that 20ox and then 3ox
o Non C13-hydroxylated pathway Same but no use of 13ox but directly 20ox
Compartmentalization
o Stage 1 chloroplast
o Stage 2 chloroplast envelope & ER
o Stage 3 Cytosol
GA inactivation (3 pathways)
o GA2-oxidase
o GA methyltransferase
o CYP714D1
Feedback
