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The topless plant developmental phenotype explained!

Osmont KS, Hardtke CS - Genome Biol. (2008)

Bottom Line: The molecular-genetic cues that regulate plant embryo pattern formation are the subject of intense scrutiny at present.Recent work in Arabidopsis implicates the TOPLESS protein in auxin-dependent transcriptional repression, highlighting once again the crucial role of auxin signaling during embryogenesis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Plant Molecular Biology, University of Lausanne, Biophore Building, CH-1015 Lausanne, Switzerland.

ABSTRACT
The molecular-genetic cues that regulate plant embryo pattern formation are the subject of intense scrutiny at present. Recent work in Arabidopsis implicates the TOPLESS protein in auxin-dependent transcriptional repression, highlighting once again the crucial role of auxin signaling during embryogenesis.

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Related in: MedlinePlus

Mutations that affect auxin-mediated apical-basal patterning in Arabidopsis and the role of TOPLESS. (a) Schematic diagram of wild-type (WT), topless (tpl), monopteros (mp), bodenlos (bdl), mp tpl, bdl tpl, and bdl mp seedling phenotypes. The temperature-sensitive tpl mutant displays apical patterning defects at permissive temperatures (24°C), whereas restrictive temperatures (29°C) result in complete homeotic transformation of the seedling shoot to root. In the double mutants, tpl can suppress patterning defects in both mp and bdl. (b) Proposed function of the TOPLESS (TPL) corepressor protein in the nucleus. TPL can homodimerize, act in a complex with IAA12/BDL and MP, and hypothetically interact with other EAR-domain-containing proteins. The CTLH domain of TPL and the EAR domain of BDL mediate the interaction between TPL and BDL. Domains III and IV of BDL are found in all AUX/IAA proteins and mediate interaction with similar domains in ARFs, such as MP.
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Figure 1: Mutations that affect auxin-mediated apical-basal patterning in Arabidopsis and the role of TOPLESS. (a) Schematic diagram of wild-type (WT), topless (tpl), monopteros (mp), bodenlos (bdl), mp tpl, bdl tpl, and bdl mp seedling phenotypes. The temperature-sensitive tpl mutant displays apical patterning defects at permissive temperatures (24°C), whereas restrictive temperatures (29°C) result in complete homeotic transformation of the seedling shoot to root. In the double mutants, tpl can suppress patterning defects in both mp and bdl. (b) Proposed function of the TOPLESS (TPL) corepressor protein in the nucleus. TPL can homodimerize, act in a complex with IAA12/BDL and MP, and hypothetically interact with other EAR-domain-containing proteins. The CTLH domain of TPL and the EAR domain of BDL mediate the interaction between TPL and BDL. Domains III and IV of BDL are found in all AUX/IAA proteins and mediate interaction with similar domains in ARFs, such as MP.

Mentions: The tpl mutation is a rare temperature-sensitive mutation that changes apical cell fate. In the first examinations of a possible role for TPL in the auxin pathway by Long et al. [2], double mutants were generated between tpl and mp. Apically, these largely resembled tpl single mutants, whereas basally they resembled mp, although the reduced hypocotyl and vascular differentiation of mp was partially suppressed by tpl (Figure 1a). When the synthetic DR5 reporter construct, which monitors ARF activity and thereby auxin concentration, was introduced into tpl embryos, it rarely displayed strong ectopic apical expression [2]. Altogether, these findings led Long et al. to suggest that disturbance in the auxin pathway could not be responsible for the tpl phenotype. However, further experiments with the TPL protein by the same laboratory [3] reveal that this assumption was premature.


The topless plant developmental phenotype explained!

Osmont KS, Hardtke CS - Genome Biol. (2008)

Mutations that affect auxin-mediated apical-basal patterning in Arabidopsis and the role of TOPLESS. (a) Schematic diagram of wild-type (WT), topless (tpl), monopteros (mp), bodenlos (bdl), mp tpl, bdl tpl, and bdl mp seedling phenotypes. The temperature-sensitive tpl mutant displays apical patterning defects at permissive temperatures (24°C), whereas restrictive temperatures (29°C) result in complete homeotic transformation of the seedling shoot to root. In the double mutants, tpl can suppress patterning defects in both mp and bdl. (b) Proposed function of the TOPLESS (TPL) corepressor protein in the nucleus. TPL can homodimerize, act in a complex with IAA12/BDL and MP, and hypothetically interact with other EAR-domain-containing proteins. The CTLH domain of TPL and the EAR domain of BDL mediate the interaction between TPL and BDL. Domains III and IV of BDL are found in all AUX/IAA proteins and mediate interaction with similar domains in ARFs, such as MP.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2643930&req=5

Figure 1: Mutations that affect auxin-mediated apical-basal patterning in Arabidopsis and the role of TOPLESS. (a) Schematic diagram of wild-type (WT), topless (tpl), monopteros (mp), bodenlos (bdl), mp tpl, bdl tpl, and bdl mp seedling phenotypes. The temperature-sensitive tpl mutant displays apical patterning defects at permissive temperatures (24°C), whereas restrictive temperatures (29°C) result in complete homeotic transformation of the seedling shoot to root. In the double mutants, tpl can suppress patterning defects in both mp and bdl. (b) Proposed function of the TOPLESS (TPL) corepressor protein in the nucleus. TPL can homodimerize, act in a complex with IAA12/BDL and MP, and hypothetically interact with other EAR-domain-containing proteins. The CTLH domain of TPL and the EAR domain of BDL mediate the interaction between TPL and BDL. Domains III and IV of BDL are found in all AUX/IAA proteins and mediate interaction with similar domains in ARFs, such as MP.
Mentions: The tpl mutation is a rare temperature-sensitive mutation that changes apical cell fate. In the first examinations of a possible role for TPL in the auxin pathway by Long et al. [2], double mutants were generated between tpl and mp. Apically, these largely resembled tpl single mutants, whereas basally they resembled mp, although the reduced hypocotyl and vascular differentiation of mp was partially suppressed by tpl (Figure 1a). When the synthetic DR5 reporter construct, which monitors ARF activity and thereby auxin concentration, was introduced into tpl embryos, it rarely displayed strong ectopic apical expression [2]. Altogether, these findings led Long et al. to suggest that disturbance in the auxin pathway could not be responsible for the tpl phenotype. However, further experiments with the TPL protein by the same laboratory [3] reveal that this assumption was premature.

Bottom Line: The molecular-genetic cues that regulate plant embryo pattern formation are the subject of intense scrutiny at present.Recent work in Arabidopsis implicates the TOPLESS protein in auxin-dependent transcriptional repression, highlighting once again the crucial role of auxin signaling during embryogenesis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Plant Molecular Biology, University of Lausanne, Biophore Building, CH-1015 Lausanne, Switzerland.

ABSTRACT
The molecular-genetic cues that regulate plant embryo pattern formation are the subject of intense scrutiny at present. Recent work in Arabidopsis implicates the TOPLESS protein in auxin-dependent transcriptional repression, highlighting once again the crucial role of auxin signaling during embryogenesis.

Show MeSH
Related in: MedlinePlus