Response to Potassium Starvation in Roots

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Response to Potassium Starvation in Roots

• Experimenter Julian Schroeder
• University of California-San Diego

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PURPOSE

• Study the response of gene expression in roots of
  25-35 day old plants.
• CONDITIONS
• Grown on hydroponics after 6, 48 and 96 hours of
  potassium starvation.

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ROOTS POTASSIUM

• Potassium is an important macronutrient and the
  most abundant cation in plants.
• Due to complex soil dynamics, plants must be able
  to adjust to different nutrient availabilities.
• A low plant potassium status
• Triggers expression of high affinity k
  transporters
• Up regulates some k channels
• Activates signalling cascades
• Molecules responsible for signalling low k
  status in plants include
• Reactive oxygen species
• Auxin
• Ethylene
• Jasmonic acid

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METHOD

• RNA from roots of mature Arabidopsis thaliana
  plants was extracted after transfer to control or
  potassium free nutrient solution.
• Affymetrix Genechip microarrays were then used to
  identify genes responsive to K deprivation in
  the roots.

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RESULTS

• With root k content reduced by 60, only a few
  genes were changed in their expression level
  after 6, 48 and 96h of k starvation.
• AtHAK5 is a potassium transporter gene from the
  KUP/HAK/KT family.
• It was most consistently and strongly up
  regulated in its expression level across 48h and
  96h deprivation experiments.
• Its promoter -ß- glucuronidase and -green
  fluorescent protein fusions showed AtHAK5
  promoter activity in the epidermis and
  vasculature of K deprived roots

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REFERENCES

• http//jxb.oxfordjournals.org/cgi/content/abstract
  /57/2/425 accessed 26 Oct 2007
• http//www.pubmedcentral.nih.gov/articlerender.fcg
  i?artid1065410 accessed 26 Oct 2007

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Line Graph representing all genes
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Scatter Plot Representation of Genes
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3-D Scatter Plot of Genes
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Pie Chart of Biological Functions
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CONCLUSION

• Apart from up-regulation of transport proteins
  and adjustment of metabolic processes, potassium
  deprivation triggers developmental responses in
  roots.
• The acclimation strategies that plants have to go
  through enable them to survive and compete for
  nutrients in a dynamic environment with a
  variable availability for potassium.