EEB340 Lecture 11.docx

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10 Apr 2012
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Lecture 10: Ancestral Tool Kit
Ancestral Tool Kit for Land Plants
Auxin and Transport
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- in the peripheral zone there is a max of Auxin where leaf primordia develop
- PIN proteins can control localized concentrations of auxin by transport
- Very low levels of auxin in algae
- Algae: auxin transport
o No polar transport
o Efflux and influx carriers
o No studies on PIN in the direct algal ancestors
- Hornworts and liverworts
o Auxin present
o No polar transport rather, movement by difussion
o No study on presence of absence of PINS
- Mosses
o Possible polar transport
o PINs present
- Selaginella
o Polar transport
o PINs present
o Protostele and microphylls
o Auxin transport directed from central region downwards
o Next get vascularization of microphylls
o Not sure if microphylls also associated with max in auzin
o Evolutionarily, may have been shift in orientation PIN proteins direct auxin,
so that transport the same way as in seed plants
o Endoplasmic reticulum and plasma membrane PINs
- Ferns
o Polar transport investigated using compounds that prevent polar
transport
o No studies on PINs
- In seed plants there are PINs specifically situated at the plasma membrane to move
auxin from cell to cell
o PINs at endoplasmic reticulum to control the concentration of auxin in the
cytoplasm can be stored in lumen of the endoplasmic reticulum
- Mosses have PINs at endoplasmic reticulum possibly ancestral
- Thought PINs at ER were transferred to plasma membrane at some point in
evolution
- PINs in PM imply a much finer control effects as auxin flows in and effect as flows
out
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