DISCOVERY OF CYTOKININS

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DISCOVERY OF CYTOKININS

• SEARCH FOR CELL DIVISION FACTORS THAT WOULD
  ALLOW PLANT TISSUES TO DIVIDE IN TISSUE CULTURE
• CELL DIVISION ACTIVITY IDENTIFIED IN COCONUT
  MILK
• CELL DIVISION ACTIVITY ALSO FOUND IN VASCULAR
  TISSUES
• ADENINE FOUND TO BE SLIGHTLY ACTIVE
• OLD BOTTLE OF DNA FOUND TO HAVE STRONG ACTIVITY,
  BUT NOT NEW BOTTLE
• KINETIN IDENTIFIED AS DEGRADATION PRODUCT OF DNA

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KINETIN (6-furfurylaminopurine)
(Discovered as a cell division factor)
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STRUCTURE OF BENZYLADENINE (BA) - ANOTHER
SYNTHETIC CYTOKININ
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trans-Zeatin(The Naturally Occurring Cytokinin)
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Biological isoprene unit
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(active form)
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CYTOKININ DEGRADATION
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EFFECT OF CYTOKININ DEFICIENCY ON GROWTH OF
TOBACCO PLANTS
Tobacco plants overexpressing gene for cytokinin
oxidase
WILD TYPE
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Wild-type Tobacco
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Tobacco overexpressing cytokinin oxidase
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Wild-type
CO Overexpressor
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Wild-type root tip
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CO Overexpressor root tip
? Cytokinin inhibits root growth
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INCREASING IAA CONCENTRATION
INCREASING CK CONCENTRATION
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OVEREXPRESSION OF Cyclin D3 (CYCD3) BYPASSES THE
CYTOKININ REQUIREMENT FOR CELL DIVISION

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Crown gall tumor on tomato stem (Agrobacterium
tumefaciens)
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• TWO MAJOR OPINES FOUND IN CROWN GALL TUMORS
• GENES FOR OPINE SYNTHESIS PRESENT ON T-DNA FROM
  AGROBACTERIUM

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Witches broom on balsam fir (Corynebacterium
fascians)
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Protonemal filaments of the moss, Funaria.
(Control)
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Protonemal filaments of the moss, Funaria.
(Treated with Benzyladenine)
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BUD FORMATION IN THE MOSS, Funaria
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EFFECT OF CYTOKININ ON LEAF SENESCENCE
CYTOKININ-TREATED
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CYTOKININ CAUSES CELLS TO BECOME SINKS
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CYTOKININ INHIBITS SENESCENCE
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CYTOKININ PROMOTES EXPANSION OF RADISH COTYLEDONS
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CYTOKININ SIGNALING INVOLVES A TWO-COMPONENT
SYSTEM
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