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A loss-of-function mutation in the nucleoporin AtNUP160 indicates that normal auxin signalling is required for a proper ethylene response in Arabidopsis.

Robles LM, Deslauriers SD, Alvarez AA, Larsen PB - J. Exp. Bot. (2012)

Bottom Line: It was subsequently determined by map-based cloning that the mutant (sar1-7) represents a loss-of-function mutation in the previously described nucleoporin AtNUP160 (At1g33410, SAR1).In support of previously reported results, the sar1-7 mutant partially restored auxin responsiveness to roots of an rce1 loss-of-function mutant, indicating that AtNUP160/SAR1 is required for proper expression of factors responsible for the repression of auxin signalling.Consistent with this, addition of auxin to ethylene-treated seedlings resulted in severe hypocotyl shortening, reminiscent of that seen for other eer (enhanced ethylene response) mutants, suggesting that auxin functions in part synergistically with ethylene to control hypocotyl elongation and other ethylene-dependent phenomena.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of California-Riverside, Riverside, CA 92521, USA.

ABSTRACT
As part of a continuing effort to elucidate mechanisms that regulate the magnitude of ethylene signalling, an Arabidopsis mutant with an enhanced ethylene response was identified. Subsequent characterization of this loss-of-function mutant revealed severe hypocotyl shortening in the presence of saturating ethylene along with increased expression in leaves of a subset of ethylene-responsive genes. It was subsequently determined by map-based cloning that the mutant (sar1-7) represents a loss-of-function mutation in the previously described nucleoporin AtNUP160 (At1g33410, SAR1). In support of previously reported results, the sar1-7 mutant partially restored auxin responsiveness to roots of an rce1 loss-of-function mutant, indicating that AtNUP160/SAR1 is required for proper expression of factors responsible for the repression of auxin signalling. Analysis of arf7-1/sar1-7 and arf19-1/sar1-7 double mutants revealed that mutations affecting either ARF7 or ARF19 function almost fully blocked manifestation of the sar1-7-dependent ethylene hypersensitivity phenotype, suggesting that ARF7- and ARF19-mediated auxin signalling is responsible for regulating the magnitude of and/or competence for the ethylene response in Arabidopsis etiolated hypocotyls. Consistent with this, addition of auxin to ethylene-treated seedlings resulted in severe hypocotyl shortening, reminiscent of that seen for other eer (enhanced ethylene response) mutants, suggesting that auxin functions in part synergistically with ethylene to control hypocotyl elongation and other ethylene-dependent phenomena.

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IAA3 is required for a normal response to ethylene. (A) Seedlings of Ler and shy2-31, which is a loss-of-function mutation affecting IAA3, were grown in the presence of 5 μM AgNO3 or 100 μl l−1 ethylene, after which hypocotyl length was measured. (B) Manifestation of the ethylene response in dark-grown seedlings of shy2-2, which represents an amino acid change that prevents auxin-dependent degradation of the repressor of auxin response IAA3, was assessed following growth for 4 d in the presence of 5 μM AgNO3 or 100 μl l−1 ethylene. (C) For the yeast two-hybrid assay, the full coding sequence of IAA3 fused to the DNA-binding domain of pLEX-NLS was tested for an interaction with the full coding sequence of ARF7 fused to the GAL4 activation domain in pACTII. The inset shows an in vitro pull-down assay in which in vitro-translated ARF7 radiolabelled with [35S]methionine was tested for its ability to interact with bacterially produced MBP fused to IAA3.
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fig6: IAA3 is required for a normal response to ethylene. (A) Seedlings of Ler and shy2-31, which is a loss-of-function mutation affecting IAA3, were grown in the presence of 5 μM AgNO3 or 100 μl l−1 ethylene, after which hypocotyl length was measured. (B) Manifestation of the ethylene response in dark-grown seedlings of shy2-2, which represents an amino acid change that prevents auxin-dependent degradation of the repressor of auxin response IAA3, was assessed following growth for 4 d in the presence of 5 μM AgNO3 or 100 μl l−1 ethylene. (C) For the yeast two-hybrid assay, the full coding sequence of IAA3 fused to the DNA-binding domain of pLEX-NLS was tested for an interaction with the full coding sequence of ARF7 fused to the GAL4 activation domain in pACTII. The inset shows an in vitro pull-down assay in which in vitro-translated ARF7 radiolabelled with [35S]methionine was tested for its ability to interact with bacterially produced MBP fused to IAA3.

Mentions: As sar1-7 had increased expression of chiB and PDF1.2 in response to ethylene, it was of interest to determine whether leaves of an arf7-1/arf19-2 double mutant had altered ethylene-dependent expression of these defence genes (Fig. 6D). The arf7-1/arf19-2 double mutant had reduced ethylene-responsive expression of both chiB and PDF1.2, which supports the argument that auxin is required to condition the ethylene response and is consistent with our observation that loss of SAR1 function and the consequent ARF7- and ARF19-dependent enhanced auxin responsiveness leads to increased expression of these genes.


A loss-of-function mutation in the nucleoporin AtNUP160 indicates that normal auxin signalling is required for a proper ethylene response in Arabidopsis.

Robles LM, Deslauriers SD, Alvarez AA, Larsen PB - J. Exp. Bot. (2012)

IAA3 is required for a normal response to ethylene. (A) Seedlings of Ler and shy2-31, which is a loss-of-function mutation affecting IAA3, were grown in the presence of 5 μM AgNO3 or 100 μl l−1 ethylene, after which hypocotyl length was measured. (B) Manifestation of the ethylene response in dark-grown seedlings of shy2-2, which represents an amino acid change that prevents auxin-dependent degradation of the repressor of auxin response IAA3, was assessed following growth for 4 d in the presence of 5 μM AgNO3 or 100 μl l−1 ethylene. (C) For the yeast two-hybrid assay, the full coding sequence of IAA3 fused to the DNA-binding domain of pLEX-NLS was tested for an interaction with the full coding sequence of ARF7 fused to the GAL4 activation domain in pACTII. The inset shows an in vitro pull-down assay in which in vitro-translated ARF7 radiolabelled with [35S]methionine was tested for its ability to interact with bacterially produced MBP fused to IAA3.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3295400&req=5

fig6: IAA3 is required for a normal response to ethylene. (A) Seedlings of Ler and shy2-31, which is a loss-of-function mutation affecting IAA3, were grown in the presence of 5 μM AgNO3 or 100 μl l−1 ethylene, after which hypocotyl length was measured. (B) Manifestation of the ethylene response in dark-grown seedlings of shy2-2, which represents an amino acid change that prevents auxin-dependent degradation of the repressor of auxin response IAA3, was assessed following growth for 4 d in the presence of 5 μM AgNO3 or 100 μl l−1 ethylene. (C) For the yeast two-hybrid assay, the full coding sequence of IAA3 fused to the DNA-binding domain of pLEX-NLS was tested for an interaction with the full coding sequence of ARF7 fused to the GAL4 activation domain in pACTII. The inset shows an in vitro pull-down assay in which in vitro-translated ARF7 radiolabelled with [35S]methionine was tested for its ability to interact with bacterially produced MBP fused to IAA3.
Mentions: As sar1-7 had increased expression of chiB and PDF1.2 in response to ethylene, it was of interest to determine whether leaves of an arf7-1/arf19-2 double mutant had altered ethylene-dependent expression of these defence genes (Fig. 6D). The arf7-1/arf19-2 double mutant had reduced ethylene-responsive expression of both chiB and PDF1.2, which supports the argument that auxin is required to condition the ethylene response and is consistent with our observation that loss of SAR1 function and the consequent ARF7- and ARF19-dependent enhanced auxin responsiveness leads to increased expression of these genes.

Bottom Line: It was subsequently determined by map-based cloning that the mutant (sar1-7) represents a loss-of-function mutation in the previously described nucleoporin AtNUP160 (At1g33410, SAR1).In support of previously reported results, the sar1-7 mutant partially restored auxin responsiveness to roots of an rce1 loss-of-function mutant, indicating that AtNUP160/SAR1 is required for proper expression of factors responsible for the repression of auxin signalling.Consistent with this, addition of auxin to ethylene-treated seedlings resulted in severe hypocotyl shortening, reminiscent of that seen for other eer (enhanced ethylene response) mutants, suggesting that auxin functions in part synergistically with ethylene to control hypocotyl elongation and other ethylene-dependent phenomena.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of California-Riverside, Riverside, CA 92521, USA.

ABSTRACT
As part of a continuing effort to elucidate mechanisms that regulate the magnitude of ethylene signalling, an Arabidopsis mutant with an enhanced ethylene response was identified. Subsequent characterization of this loss-of-function mutant revealed severe hypocotyl shortening in the presence of saturating ethylene along with increased expression in leaves of a subset of ethylene-responsive genes. It was subsequently determined by map-based cloning that the mutant (sar1-7) represents a loss-of-function mutation in the previously described nucleoporin AtNUP160 (At1g33410, SAR1). In support of previously reported results, the sar1-7 mutant partially restored auxin responsiveness to roots of an rce1 loss-of-function mutant, indicating that AtNUP160/SAR1 is required for proper expression of factors responsible for the repression of auxin signalling. Analysis of arf7-1/sar1-7 and arf19-1/sar1-7 double mutants revealed that mutations affecting either ARF7 or ARF19 function almost fully blocked manifestation of the sar1-7-dependent ethylene hypersensitivity phenotype, suggesting that ARF7- and ARF19-mediated auxin signalling is responsible for regulating the magnitude of and/or competence for the ethylene response in Arabidopsis etiolated hypocotyls. Consistent with this, addition of auxin to ethylene-treated seedlings resulted in severe hypocotyl shortening, reminiscent of that seen for other eer (enhanced ethylene response) mutants, suggesting that auxin functions in part synergistically with ethylene to control hypocotyl elongation and other ethylene-dependent phenomena.

Show MeSH
Related in: MedlinePlus