Studies on the role of the Arabidopsis gene MONOPTEROS in vascular development and plant cell axialization

Przemeck, Gerhard K. H.; Mattsson, Jim; Hardtke, Christian S.; Sung, Z. Renee; Berleth, Thomas

doi:10.1007/bf00208313

Cited by 439 publications

(353 citation statements)

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“…Recently, several genetic and physiological studies strongly suggested that auxin transport and auxin response are required for normal embryogenesis (Przemeck et al, 1996;Hadfi et al, 1998;Hamann et al, 1999; Chen et al, 2001). Our studies show that AXR1 and ECR1 are expressed during embryo development, despite the fact that axr1 embryos do not have an obvious defect.…”

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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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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“…Because it is known that auxin plays an essential role in the patterning of vascular tissues (Przemeck et al, 1996;Hardtke and Berleth, 1998), possible alterations to auxin-cytokinin interactions in the pls mutant, which are attributable to increased cytokinin levels or sensitivity or reduced auxin levels or sensitivity, could account for the observed reduced vascularization in the pls leaf.…”

Section: Pls Functionmentioning

confidence: 99%

The POLARIS Gene of Arabidopsis Encodes a Predicted Peptide Required for Correct Root Growth and Leaf Vascular Patterning

et al. 2002

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The POLARIS ( PLS ) gene of Arabidopsis was identified as a promoter trap transgenic line, showing ␤ -glucuronidase fusion gene expression predominantly in the embryonic and seedling root, with low expression in aerial parts. Cloning of the PLS locus revealed that the promoter trap T-DNA had inserted into a short open reading frame (ORF). Rapid amplification of cDNA ends PCR, RNA gel blot analysis, and RNase protection assays showed that the PLS ORF is located within a short ( ‫ف‬ 500 nucleotides) auxin-inducible transcript and encodes a predicted polypeptide of 36 amino acid residues. pls mutants exhibit a short-root phenotype and reduced vascularization of leaves. pls roots are hyperresponsive to exogenous cytokinins and show increased expression of the cytokinin-inducible gene ARR5 / IBC6 compared with the wild type. pls seedlings also are less responsive to the growth-inhibitory effects of exogenous auxin and show reduced expression of the auxin-inducible gene IAA1 compared with the wild type. The PLS peptide-encoding region of the cDNA partially complements the pls mutation and requires the PLS ORF ATG for activity, demonstrating the functionality of the peptide-encoding ORF. Ectopic expression of the PLS ORF reduces root growth inhibition by exogenous cytokinins and increases leaf vascularization. We propose that PLS is required for correct auxin-cytokinin homeostasis to modulate root growth and leaf vascular patterning.

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“…Appropriate distribution of auxin has been shown to be necessary for a number of developmental processes. Normal embryogenesis, for example, requires auxin transport (Cooke et al, 1993), and the Arabidopsis mutants lop1, pin1-1, and monopterous (Okada et al, 1991;Carland and McHale, 1996;Przemeck et al, 1996), which may be altered in auxin transport, have altered vascular, floral, and pattern development, respectively.…”

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confidence: 99%

Inhibition of Auxin Movement from the Shoot into the Root Inhibits Lateral Root Development in Arabidopsis

1998

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In roots two distinct polar movements of auxin have been reported that may control different developmental and growth events. To test the hypothesis that auxin derived from the shoot and transported toward the root controls lateral root development, the two polarities of auxin transport were uncoupled in Arabidopsis. Local application of the auxin-transport inhibitor naphthylphthalamic acid (NPA) at the root-shoot junction decreased the number and density of lateral roots and reduced the free indoleacetic acid (IAA) levels in the root and [ 3 H]IAA transport into the root. Application of NPA to the basal half of or at several positions along the root only reduced lateral root density in regions that were in contact with NPA or in regions apical to the site of application. Lateral root development was restored by application of IAA apical to NPA application. Lateral root development in Arabidopsis roots was also inhibited by excision of the shoot or dark growth and this inhibition was reversible by IAA. Together, these results are consistent with auxin transport from the shoot into the root controlling lateral root development.

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Studies on the role of the Arabidopsis gene MONOPTEROS in vascular development and plant cell axialization

Cited by 439 publications

References 10 publications

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

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

The POLARIS Gene of Arabidopsis Encodes a Predicted Peptide Required for Correct Root Growth and Leaf Vascular Patterning

Inhibition of Auxin Movement from the Shoot into the Root Inhibits Lateral Root Development in Arabidopsis

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