The Arabidopsis gene MONOPTEROS encodes a transcription factor mediating embryo axis formation and vascular development

Hardtke, Christian S.; Berleth, Thomas

doi:10.1093/emboj/17.5.1405

Cited by 942 publications

(789 citation statements)

References 28 publications

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“…For example, manipulation of the amount and spatial distribution of auxin (Liu et al 1993;Fischer and Neuhaus 1996;Hadfi et al 1998) in developing zygotic embryos phenocopies development observed in a number of embryo defective mutants (Mayer et al 1991). Many em-bryo-patterning mutants have altered auxin sensitivities or are associated with auxin signal transduction (Hardtke and Berleth 1998;Hammann et al 1999;Hobbie et al 2000) beginning as early as the primary zygotic division. Unlike the established role for auxin in embryogenesis, the receptor(s) mediating any auxin action is unclear.…”

Section: Discussionmentioning

confidence: 99%

ABP1 is required for organized cell elongation and division in Arabidopsis embryogenesis

Chen

Ullah²,

Young³

et al. 2001

Genes Dev.

299

246

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To directly address the function of a putative auxin receptor designated ABP1, a reverse genetic approach was taken to identify and characterize ABP1 mutant alleles in Arabidopsis. A homozygous null mutation in ABP1 confers embryo lethality. Null mutant embryos develop normally until the early stages of the globular embryo but are unable to make the transition to a bilaterally symmetrical structure because cells fail to elongate. Cell division was also aberrant both in the suspensor and embryo proper. Antisense suppression of ABP1 in tobacco cells causes slow proliferation and eliminates auxin-induced cell elongation and reduces cell division. The complete lack of auxin-inducible elongation in individual cells confirms the results observed in embryos, indicates a cell autonomous function, and, taken together with biochemical evidence that ABP1 binds auxins, suggests that ABP1 mediates auxin-induced cell elongation and, directly or indirectly, cell division.

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Section: Discussionmentioning

confidence: 99%

ABP1 is required for organized cell elongation and division in Arabidopsis embryogenesis

Chen

Ullah²,

Young³

et al. 2001

Genes Dev.

299

246

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“…In addition, bdl axr1 embryos resemble the embryonic mutant monopteros (mp) or wild-type embryos exposed to auxin transport inhibitors during embryogenesis (Hadfi et al, 1998). MP encodes a transcription factor (IAA24) that binds to the promoter elements of auxin-regulated genes (Ulmasov et al, 1997;Hardtke and Berleth, 1998). We have shown recently that overexpression of a mutant stabilized form of IAA7/AXR2 called axr2-1 in an axr1-3 background results in a mp phenotype (Gray et al, 2001).…”

Section: Function Of Axr1-ecr1 During Embryogenesismentioning

confidence: 99%

AXR1-ECR1–Dependent Conjugation of RUB1 to the Arabidopsis Cullin AtCUL1 Is Required for Auxin Response

et al. 2002

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Mutations in the AXR1 gene result in a reduction in auxin response and diverse defects in auxin-regulated growth and development. In a previous study, we showed that AXR1 forms a heterodimer with the ECR1 protein. This enzyme activates the ubiquitin-related protein RUB1 in vitro. Furthermore, we showed that the Skp1-Cul1/Cdc53-F-box (SCF) subunit AtCUL1 is modified by RUB1 in vivo. In this report, we demonstrate that the formation of RUB-AtCUL1 is dependent on AXR1 and ECR1 in vivo. The expression of AXR1 and ECR1 is restricted to zones of active cell division and cell elongation, consistent with their role in growth regulation. These results provide strong support for a model in which RUB conjugation of AtCUL1 affects the function of SCF E3s that are required for auxin response. INTRODUCTIONIndole-3-acetic acid (IAA or auxin) is an important regulator of plant growth and development. Auxin is implicated in many growth processes, ranging from embryogenesis to floral development (Davies, 1995). In addition, auxin plays a principal role in the control of cell division and elongation (Evans, 1984;Gray et al., 1998Gray et al., , 1999. Despite the importance of this hormone, the molecular mechanisms of auxin action are poorly defined. In an attempt to elucidate these mechanisms, several groups have taken a genetic approach by screening for Arabidopsis mutants with defects in auxin response (Hobbie et al., 1994). One of the mutants recovered in these screens, called axr1 , has a pleiotropic phenotype related to decreased auxin response. Mutant plants have reduced apical dominance, fewer lateral roots and root hairs, low fertility, and reduced gravitropic response (Lincoln et al., 1990). In addition, members of the Aux/IAA and SAUR families of auxin-regulated genes are not expressed normally in the mutant, suggesting that AXR1 functions in auxin signal transduction (Abel et al., 1995;Timpte et al., 1995).AXR1 encodes a subunit of a heterodimeric RUB-activating enzyme (del Pozo et al., 1998). Biochemical studies suggest that a protein called ECR1 is the second subunit in this enzyme (del Pozo et al., 1998). RUB (or NEDD8 in humans) is a small ubiquitin-related protein that is conjugated to cellular proteins via a pathway similar to the ubiquitin conjugation pathway. At present, the only known targets of RUB modification are members of the cullin family (del Pozo et al., 1998;Lammer et al., 1998;Osaka et al., 1998;del Pozo and Estelle, 1999;Liakopoulos et al., 1999;Wada et al., 1999). Cullins are subunits of an E3-ubiquitin ligase complex called the Skp1-Cul1/Cdc53-F-box (SCF). The other subunits of the complex are SKP1, RBX1, and an F-box protein (Patton et al., 1998;Kamura et al., 1999). The SCF promotes the transfer of ubiquitin from a ubiquitin-conjugating enzyme (E2) to a target protein. The function of RUB modification of cullin is unknown. Unlike ubiquitination, RUB modification of the cullin does not affect its metabolic stability. Instead, genetic and biochemical evidence suggests that RUB modification regulate...

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“…There is currently very little known about the function of most ARF family members other than NPH4/ARF7 with the exception of a small handful. Through loss of function mutant analysis we know that ETTIN(ET)/ ARF3 is necessary for auxin-dependent pattern formation of the gynoecium (Nemhauser et al, 2000;Sessions et al, 1997) and that MONOPTEROS(MP)/ARF5 plays a role in vascular tissue patterning and differentiation (Hardtke and Berleth, 1998).…”

Section: Saw the Lightmentioning

confidence: 99%

Plant tropisms: providing the power of movement to a sessile organism

Esmon¹,

Pedmale²,

Liscum³

2005

Int. J. Dev. Biol.

108

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In an attempt to compensate for their sessile nature, plants have developed growth responses to deal with the copious and rapid changes in their environment. These responses are known as tropisms and they are marked by a directional growth response that is the result of differential cellular growth and development in response to an external stimulation such as light, gravity or touch. While the mechanics of tropic growth and subsequent development have been the topic of debate for more than a hundred years, only recently have researchers been able to make strides in understanding how plants perceive and respond to tropic stimulations, thanks in large part to mutant analysis and recent advances in genomics. This paper focuses on the recent advances in four of the best-understood tropic responses and how each affects plant growth and development: phototropism, gravitropism, thigmotropism and hydrotropism. While progress has been made in deciphering the events between tropic stimulation signal perception and each characteristic growth response, there are many areas that remain unclear, some of which will be discussed herein. As has become evident, each tropic response pathway exhibits distinguishing characteristics. However, these pathways of tropic perception and response also have overlapping components -a fact that is certainly related to the necessity for pathway integration given the everchanging environment that surrounds every plant.

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The Arabidopsis gene MONOPTEROS encodes a transcription factor mediating embryo axis formation and vascular development

Cited by 942 publications

References 28 publications

ABP1 is required for organized cell elongation and division in Arabidopsis embryogenesis

ABP1 is required for organized cell elongation and division in Arabidopsis embryogenesis

AXR1-ECR1–Dependent Conjugation of RUB1 to the Arabidopsis Cullin AtCUL1 Is Required for Auxin Response

Plant tropisms: providing the power of movement to a sessile organism

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