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Slide 2 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 (GA 3 ) Slide 3 Slide 4 Slide 5 Slide 6 Slide 7 Rice leaf sheath bioassay for gibberellin Increasing GA 3 concentration Slide 8 GIBBERELLIN BIOSYNTHESIS AND METABOLISM 1.GIBBERELLINS ARE SYNTHESIZED VIA THE TERPENOID PATHWAY. 2. BASED ON ISOPRENE UNITS: 3.BIOLOGICAL ISOPRENE UNIT = ISOPENTENYL DIPHOSPHATE Slide 9 Slide 10 Slide 11 Slide 12 LOCATIONS OF SOME MUTANT GENES THAT BLOCK GA BIOSYNTHETIC PATHWAY IN PEA Slide 13 GA 1, THE BIOLOGICALLY ACTIVE GIBBERELLIN, IS SYNTHESIZED FROM GA 20 Slide 14 GA 1 LEVELS CORRELATE WITH INTERNODE LENGTH Slide 15 Phenotypes and genotypes of peas with different gibberellin levels Slide 16 Luciferase reporter construct for GA 20-oxidase HIGHEST IN APICAL BUD Slide 17 EFFECT OF AMO-1618 ON PETIOLE ELONGATION OF SPINACH Slide 18 EFFECT OF LONG DAYS ON GA LEVELS IN SPINACH Slide 19 Long DaysShort Days Effect of Long Days (High GA levels) on Tuber Formation in Potato Slide 20 Genetically Engineered Dwarf Wheat Plants Overexpressing GA 2-ox, which degrades GA 1 Slide 21 KINETICS OF GA-INDUCED ELNGATION OF DEEPWATER RICE INTERNODE 30 min Slide 22 DISTRIBUTION OF CELL DIVISION FOLLOWING GA TREATMENT OF A ROSETTE PLANT, Samolus parviflorus Slide 23 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) Slide 24 Slide 25 GAI and RGA are related repressor proteins Repression of GA Response Genes GA Response Genes Expressed Slide 26 DIFFERENT TYPES OF MUTATIONS OF GAI AND RGA REPRESSORS AFFECT GROWTH DIFFERENTLY Slide 27 Enzyme involved in protein modification - enhances activity of GAI and RGA GA acts to block action of both SPY and GAI/RGA Slide 28 THE CEREAL ALEURONE LAYER Slide 29 Slide 30 Slide 31 Slide 32 Slide 33 Slide 34 EFFECT OF GA ON CALCIUM IN BARLEY ALEURONE LAYER PROTOPLAST CONTROL + GA 3 GA 3 + ABA (ABSCISIC ACID) Low Cytoplasmic [Ca2+] High Slide 35 SUMMARY OF STEPS IN GA SIGNAL TRANSDUCTION PATHWAY