Basic Hormone Treatment of Seeds An AtGenExpress Experiment on Arabidopsis thaliana

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Basic Hormone Treatment of SeedsAn AtGenExpress
Experiment on Arabidopsis thaliana

• Chijioke Elekwachi
• University of Nottingham, School of Biosciences
• Sutton Bonnington, Loughborough. UK
• Module D2DPG1 Coursework

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Introduction

• Gibberellins are plant hormones thought to
  influence aspects of the plant development
  process, including
• Cell division Stem elongation
• Fruit/Leaf development (senescence)
• Flowering Sex expression (maleness in dioecious
  flowers)
• Breaking of seed/bud dormancy Germination
• Information on its actual mechanism of operation,
  the genes involved in its control, and the
  dynamics of such genes/activity is however
  sparse.

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Project Objectives

• This study seeks to investigate the influence of
  hormone treatment of the seeds of Arabidopsis
  thaliana on the transcriptomics of the plant
• Specifically, to identify (if possible) genes
  whose expression might have been modulated (up or
  down) in response to treatment with gibberellins.
• To determine the expression pattern of such genes
  

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Design

• Seeds of Arabidopsis thaliana were treated with
  hormone solution
• Treatments
• 5µM Gibberellin Solution
• Water (Control)
• Times
• 3hr 6hrs 9hrs
• Replicates 3
• Samples hybridized to Affymetrix ATH1 Arabidopsis
  Genome Array

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Results

• Volcano Plots
• Compared significant changes in gene expression
  btw treated samples and the control (water) at
  each of the specified time intervals.Fold
  change 1.5 p-value 0.05.

3hrs 5µM gibberellin/3hrs Water Genes sigf.
expressed 84
6hrs 5µM gibberellin/6hrs Water Genes sigf.
expressed 372
9hrs 5µM gibberellin/9hrs Water Genes sigf.
expressed 869
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Results

• Identification of Genes of interest
• Genes whose expression changed significantly at
  the specified fold change delimitation throughout
  the three time periods under investigation.

22 candidate genes were identified.
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Results

• Cluster Analysis (K Means / Gene Tree)

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Results

• Candidate genes included
• a transcription factor,
• three auxin or gibberellin-induced proteins, and
• other protein/enzyme families involved in
  physiological processes like root nodule
  development, glucose transportation etc..

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Results

• Considerations from Gene Ontology

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Conclusions

• Exposure to gibberellins resulted in the
  modulation of a number of A. thaliana genes the
  number increasing with increasing exposure time.
  The expression profile of about 22 genes
  significantly changed through out the experiment.
• Gibberellins therefore have been shown to play
  some role in seed germination of Arabidopsis
• The study also suggests that this
  hormone-mediated control involves
• Synthesis and biogenesis
• Response
• Cell metabolic activities
• Cell signalling and transport.

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Possible next steps

• Possibly look at influence of different light
  regimes in addition to Gibberellins, on breaking
  of seed dormancy and germination in some plants.

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Thank you