1. DISCOVERY OF GIBBERELLINS
“BAKANAE” OR “FOOLISH SEEDLING” DISEASE OF RICE : plants grew too talkk and toppled over.
JAPANESE SCIENTISTS WORKED ON THE PROBLEM AND IDENTIFIED CAUSE: INFECTION BY FUNGUS, GIBBERELLA FUJUKUROI.
MID 1950s: ACTIVE SUBSTANCE CRYTALIZED AND IDENTIFIED IN ENGLAND AND US: GIBBERELLIC ACID (GA3)

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6. Rice leaf sheath bioassay for gibberellin
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Increasing GA3 concentration

7. GIBBERELLIN BIOSYNTHESIS AND METABOLISM
GIBBERELLINS ARE SYNTHESIZED VIA THE TERPENOID PATHWAY.
BASED ON ISOPRENE UNITS:
BIOLOGICAL ISOPRENE UNIT = ISOPENTENYL DIPHOSPHATE

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11. LOCATIONS OF SOME MUTANT GENES THAT BLOCK GA BIOSYNTHETIC PATHWAY IN PEA
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12. GA1, THE BIOLOGICALLY ACTIVE GIBBERELLIN, IS SYNTHESIZED FROM GA20
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13. GA1 LEVELS CORRELATE WITH INTERNODE LENGTH
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14. Phenotypes and genotypes of peas with different gibberellin levels
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15. Luciferase reporter construct for GA 20-oxidase
HIGHEST IN APICAL BUD
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16. EFFECT OF AMO-1618 ON PETIOLE ELONGATION OF SPINACH
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17. EFFECT OF LONG DAYS ON GA LEVELS IN SPINACH
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18. Effect of Long Days (High GA levels) on Tuber Formation in Potato
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Long Days
Short Days

19. Genetically Engineered Dwarf Wheat Plants Overexpressing GA 2-ox, which degrades GA1
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20. KINETICS OF GA-INDUCED ELNGATION OF DEEPWATER RICE INTERNODE
30 min
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21. DISTRIBUTION OF CELL DIVISION FOLLOWING GA TREATMENT OF A ROSETTE PLANT, Samolus parviflorus
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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)

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24. GAI and RGA are related repressor proteins
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Repression of GA Response Genes
GA Response Genes Expressed

25. DIFFERENT TYPES OF MUTATIONS OF GAI AND RGA REPRESSORS AFFECT GROWTH DIFFERENTLY
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26. GA acts to block action of both SPY and GAI/RGA
Enzyme involved in protein modification - enhances activity of GAI and RGA
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27. THE CEREAL ALEURONE LAYER
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THE CEREAL ALEURONE LAYER

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33. EFFECT OF GA ON CALCIUM IN BARLEY ALEURONE LAYER PROTOPLAST
CONTROL GA GA3 + ABA (ABSCISIC ACID)
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Low Cytoplasmic [Ca2+] High

34. SUMMARY OF STEPS IN GA SIGNAL TRANSDUCTION PATHWAY
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