wang yuqian
DESCRIPTION
A small acidic protein 1 (SMAP1) mediates responses of the Arabidopsis root to the synthetic auxin 2,4-dichlorophenoxyacetic acid. Wang Yuqian. Introduction Result Discussion. introduction. The functions of auxin The mechanism of auxin signal transduction Unknown. TIR1. auxin. SCF TIR1. - PowerPoint PPT PresentationTRANSCRIPT
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A small acidic protein 1 (SMAP1) mediates responses of the
Arabidopsis root to the synthetic auxin
2,4-dichlorophenoxyacetic acid
A small acidic protein 1 (SMAP1) mediates responses of the
Arabidopsis root to the synthetic auxin
2,4-dichlorophenoxyacetic acid
Wang Yuqian
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IntroductionResultDiscussion
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introduction
The functions of auxin The mechanism of auxin
signal transduction Unknown
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G protein ?
exogenous auxin concentration ?
polar auxin
transport ?
a component of a multisubunit E3
ubiquitin ligase
SCFTIR1
AUX/IAA
a large
family of
regulatory proteins
TIR1auxin
ARFsauxin response factors
transcription factors
Gene expression
auxin receptor
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Result1. Identification of the aar1-1 mutant
2. Root elongation, lateral root induction, and germination
in aar1-1 are resistant specifically to 2,4-D
3. Auxin-dependent gene expression and proteolysis in
aar1-1
4. Uptake and metabolism of 2,4-D are unaltered in aar1-1
5. At4g13520 mediates PCIB and 2,4-D responsiveness
6. At4g13520 encodes a small, acidic protein of unknown
function
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Result
1. Identification of the aar1-1 mutant
1) grow under PCIB (p-chlorophenoxyisobutyric acid)
2) select the one with longer root
3) re-screen after several generations of selfing
4) get antiauxin resistant1 (aar1-1)
5) backcrossing with WT and selfing to get F2
6) 3:1
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11-day-old light-grown seedlings. 10-day-old light-grown seedlings exposed to 20 uM PCIB
Figure 1. Photographs illustrating seedling phenotypes of wild-type (WT) and aar1-1.
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Result
2. Root elongation in aar1-1 are resistant specifically to 2,4-D
Figure 2. Root elongation versus concentration of IAA and 2,4-D.
Conclusion: For root growth, aar1-1 responds like wild-type to IAA
but is resistant to 2,4-D.
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Result3. Auxin-dependent gene expression and proteolysis in
aar1-1
Figure 3. DR5:GUS expression in wild-type and aar1-1 in response to IAA and 2,4-D. Seedlings were exposed to the auxins in liquid for 6 h.
Conclusion: IAA stimulated DR5:GUS expression similarly in both genotypes, whereas 2,4-D at all concentrations was less effective in aar1-1 compared to the wild-type.
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Conclusion: AAR1 is a component of a
response pathway that
recognizes 2,4-D specifically
Figure 4. Real-time PCR analysis of the expression of the IAA11 gene in wildtype and aar1-1.
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Result
4. Uptake and metabolism of 2,4-D are unaltered in aar1-1
Conclusion: The accumulation of 2,4-D was indistinguishable in wild-type and aar1-1 .
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Figure 6. Metabolism of 2,4-D in wild-type and aar1-1.
Conclusion: There was no change in the amount of radioactivity in any of the three resolved fractions, with the great majority remaining unmetabolized (fraction C), suggesting that the metabolism of 2,4-D is not altered in aar1-1.
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Result5. At4g13520 mediates PCIB and 2,4-D responsiveness
Figure 7. Maps of the aar1 locus and of constructs used for complementation.
1. The region deleted in aar1-1 is indicated by the red box.
2. The structure of the enhancer-trap insertion in aar1-2 is shown.
3. Annotated open reading frames are shown as black boxes.
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Construct
Transfection
Expression in aar1
2,4-D response
2,4-D resistant X
√
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Figure 9. RNAi experiments.
The RNAi results, taken together with the complementation and the isolation of aar1-2, indicate that At4g13520 confers sensitivity to PCIB and 2,4-D.
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Result6. At4g13520 encodes a small, acidic protein of unknown
function
Figure 10. Alignment of putative SMAP1 homologues.
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Discussion
1. Collectively, these results indicate that the auxin transport machinery functions as normal in this mutant, and the specific resistance of aar1 towards 2,4-D and PCIB seems not to be due to an alteration in transport of these compounds.
2. The aar1 mutant and the SMAP1 gene provide genetic evidence that 2,4-D has a distinct response pathwayfrom IAA.
3. SMAP1 may be an accessory protein that stabilizes the auxin signaling complex, and 2,4-D action in this complex is more sensitive to loss of SMAP1 than is IAA action.
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Thank you!Thank you!