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Mutations that a fg ect auxin tra ffj c or perception give rise to - - PowerPoint PPT Presentation
Mutations that a fg ect auxin tra ffj c or perception give rise to - - PowerPoint PPT Presentation
2018 CDB Part IB Plant Development Lecture 2. Polarity and auxin fm ow Jim Haseloff Department of Plant Sciences Mutations that a fg ect auxin tra ffj c or perception give rise to plants with altered body plans Charles and Francis
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Charles and Francis Darwin’s experiments on signalling during plant phototropism
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Demonstration of chemical signaling
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Auxin and apical-basal polarity: Apical-basal polarity and the coordination of indeterminate growth and branching in plants is maintained by traffic of growth regulators. These are not passive gradients, but are the product of active cellular transport.
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HA H+ A-
The pathway of auxin traffic through the plant is determined by the activities of influx and efflux carriers.
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Auxin influx carrier: AUX1
The aux1 mutant confers resistance to the herbicide 2,4-D, an auxin mimic
WT WT aux1 aux1 2,4-D 1-NAA
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WT pin1
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PIN1 auxin efflux carrier
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(upper cell) (lower cell) (cell wall)
PIN1 is plasma membrane localised with a polar distribution within the cell
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Auxin fmow and accumulation regulates patterning in the embryo
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Immunolocalisation of PIN4 in Arabidopsis embryos Immunolocalisation of PIN7 in Arabidopsis embryos
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Changes in PIN1 in distribution during Arabidopsis embryogenesis
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Auxin triggered gene expression during embryogenesis DR5::GFP
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Mutations that affect auxin traffic or perception give rise to plants with altered body plans.
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wild type Immunolocalisation of PIN1 in Arabidopsis embryos gnom mutant
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Feedback through regulated expression and localisation of PIN genes
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Asymmetric localisation of the PIN1 auxin efflux transporter is a dynamic process and requires the maintenance of polar secretion.
Brefeldin A treatment causes rapid loss of PIN1 localisation.
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untreated PIN1-GFP PIN1-GFP PM-ATPase PIN2-GFP
Application of auxin reverses the effect of Brefeldin A (BFA)
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Brefeldin A
- r
gnom mutant
x x
Auxin
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Inhibition of auxin transport by application of NPA
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Defects in auxin transport or response affect patterning of the plant vascular system
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“Canalisation” of auxin flow
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Auxin flux
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PIN1 localisation
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pin2 mutant seedlings show loss of gravitropism in the root
Family of PIN genes in the Arabidopsis root
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PIN2 localisation
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PIN3 localisation PIN4 localisation
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PIN1 PIN3 PIN4 PIN2 PIN2
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Polar fmux of auxin controls cell fate and organisation in the Arabidopsis root + NPA auxin fmux inhibitor control
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PIN1 PIN3 PIN4 PIN2 PIN2
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Gravity and PIN3 mediated redirection of auxin fmow at the root tip regulates the direction of root growth
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It provides both long-range coordination of plant architecture, and a short-range mechanism for controlling individual cell fates.
- Embryo polarity and outgrowth
- Root and shoot meristem
- utgrowth
- Vascular development
Feedback-regulated traffic of auxin coordinates polar growth of plant cells
“Canalisation” of auxin flow
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