3. DISCOVERY OF GIBBERELLINS
1. “BAKANAE” OR “FOOLISH SEEDLING” DISEASE OF RICE : plants grew
too talkk and toppled over.
2. JAPANESE SCIENTISTS WORKED ON THE PROBLEM AND IDENTIFIED
CAUSE: INFECTION BY FUNGUS, GIBBERELLA FUJUKUROI.
3. MID 1950s: ACTIVE SUBSTANCE CRYTALIZED AND IDENTIFIED IN
ENGLAND AND US: GIBBERELLIC ACID (GA3)
7. GIBBERELLIN BIOSYNTHESIS AND METABOLISM
1. GIBBERELLINS ARE SYNTHESIZED VIA THE TERPENOID
PATHWAY.
2. BASED ON ISOPRENE UNITS:
3. BIOLOGICAL ISOPRENE UNIT = ISOPENTENYL DIPHOSPHATE
8.
9.
10.
11. LOCATIONS OF
SOME MUTANT
GENES THAT
BLOCK GA
BIOSYNTHETIC
PATHWAY IN
PEA
21. DISTRIBUTION OF CELL DIVISION FOLLOWING GA TREATMENT OF
A ROSETTE PLANT, Samolus parviflorus
22. Arabidopsis GIBBERELLIN RESPONSE MUTANTS WITH
DEFECTS IN SIGNAL TRANSDUCTION
1. Gibberellin-in sensitive dwarfs
2. Gibberellin-deficient mutants in which GA deficiency
has been overcome by a second suppressor mutation,
so plant looks normal (double mutant)
3. Mutants with constitutive gibberellin response
(“slender” mutants)
23.
24. GAI and RGA are related repressor proteins
Repression of GA
Response Genes
GA Response
Genes
Expressed
25. DIFFERENT TYPES OF MUTATIONS OF GAI AND RGA
REPRESSORS AFFECT GROWTH DIFFERENTLY
26. Enzyme
involved in
protein
modification -
enhances
activity of
GAI and RGA
GA acts to
block action
of both SPY
and
GAI/RGA