Limits...
The Arabidopsis AtRaptor genes are essential for post-embryonic plant growth.

Anderson GH, Veit B, Hanson MR - BMC Biol. (2005)

Bottom Line: AtRaptor transcripts accumulate in dividing and expanding cells and tissues.The data implicate the TOR signaling pathway, a major regulator of cell growth in yeast and metazoans, in the maintenance of growth from the shoot apical meristem in plants.These results provide insights into the ways in which TOR/Raptor signaling has been adapted to regulate plant growth and development, and indicate that in plants, as in other eukaryotes, there is some Raptor-independent TOR activity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Molecular Biology and Genetics, Cornell University, Ithaca, 14853, USA. ganderson@salk.edu

ABSTRACT

Background: Flowering plant development is wholly reliant on growth from meristems, which contain totipotent cells that give rise to all post-embryonic organs in the plant. Plants are uniquely able to alter their development throughout their lifespan through the generation of new organs in response to external signals. To identify genes that regulate meristem-based growth, we considered homologues of Raptor proteins, which regulate cell growth in response to nutrients in yeast and metazoans as part of a signaling complex with the target of rapamycin (TOR) kinase.

Results: We identified AtRaptor1A and AtRaptor1B, two loci predicted to encode Raptor proteins in Arabidopsis. Disruption of AtRaptor1B yields plants with a wide range of developmental defects: roots are thick and grow slowly, leaf initiation and bolting are delayed and the shoot inflorescence shows reduced apical dominance. AtRaptor1A AtRaptor1B double mutants show normal embryonic development but are unable to maintain post-embryonic meristem-driven growth. AtRaptor transcripts accumulate in dividing and expanding cells and tissues.

Conclusion: The data implicate the TOR signaling pathway, a major regulator of cell growth in yeast and metazoans, in the maintenance of growth from the shoot apical meristem in plants. These results provide insights into the ways in which TOR/Raptor signaling has been adapted to regulate plant growth and development, and indicate that in plants, as in other eukaryotes, there is some Raptor-independent TOR activity.

Show MeSH

Related in: MedlinePlus

AtRaptor loci and insertion allele characterization. (A) AtRaptor1A and AtRaptor1B loci. Genomic sequence is depicted as a thin central line. Thick blocks indicate exons. Coding exons span the central line; exons encoding untranslated regions are fully below the central line. The positions of the T-DNA insertions are depicted with inverted triangles. (B) Reverse-Transcribed RNA-template Polymerase Chain Reactions (RT-PCR) on plants homozygous for both wild-type AtRaptor alleles (Col), the AtRaptor1A insertion allele (A-) or the AtRaptor1B insertion allele (B-), using primers spanning the AtRaptor1A insertion site, the AtRaptor1B insertion site, or control primers. Both AtRaptor insertion alleles abolish accumulation of the wild-type transcript from their locus.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC1131892&req=5

Figure 2: AtRaptor loci and insertion allele characterization. (A) AtRaptor1A and AtRaptor1B loci. Genomic sequence is depicted as a thin central line. Thick blocks indicate exons. Coding exons span the central line; exons encoding untranslated regions are fully below the central line. The positions of the T-DNA insertions are depicted with inverted triangles. (B) Reverse-Transcribed RNA-template Polymerase Chain Reactions (RT-PCR) on plants homozygous for both wild-type AtRaptor alleles (Col), the AtRaptor1A insertion allele (A-) or the AtRaptor1B insertion allele (B-), using primers spanning the AtRaptor1A insertion site, the AtRaptor1B insertion site, or control primers. Both AtRaptor insertion alleles abolish accumulation of the wild-type transcript from their locus.

Mentions: To gain insight into the function of the AtRaptor proteins, we searched for insertion alleles of each locus among the publicly available sequenced T-DNA insertion lines. Insertion mutant lines SALK_043920 and SALK_078159, with disruptions to the AtRaptor1A and AtRaptor1B loci, were obtained from the Arabidopsis Biological Resource Center (USA). Lines homozygous for each insertion (referred to as 1A -/- and 1B -/-, respectively) were identified via polymerase chain reaction (PCR), and RNA from floral buds of insertion homozygotes was used for reverse-transcriptase-PCR (RT-PCR) to assay for accumulation of wild-type transcripts from the disrupted locus. AtRaptor1A transcripts could not be detected in 1A -/- buds, but were detected in 1B -/- buds. AtRaptor1B transcripts were not detected in 1B -/- buds, but were detected in 1A -/- buds. Both transcripts were detected in wild-type Columbia (Col) buds (Fig. 2).


The Arabidopsis AtRaptor genes are essential for post-embryonic plant growth.

Anderson GH, Veit B, Hanson MR - BMC Biol. (2005)

AtRaptor loci and insertion allele characterization. (A) AtRaptor1A and AtRaptor1B loci. Genomic sequence is depicted as a thin central line. Thick blocks indicate exons. Coding exons span the central line; exons encoding untranslated regions are fully below the central line. The positions of the T-DNA insertions are depicted with inverted triangles. (B) Reverse-Transcribed RNA-template Polymerase Chain Reactions (RT-PCR) on plants homozygous for both wild-type AtRaptor alleles (Col), the AtRaptor1A insertion allele (A-) or the AtRaptor1B insertion allele (B-), using primers spanning the AtRaptor1A insertion site, the AtRaptor1B insertion site, or control primers. Both AtRaptor insertion alleles abolish accumulation of the wild-type transcript from their locus.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1131892&req=5

Figure 2: AtRaptor loci and insertion allele characterization. (A) AtRaptor1A and AtRaptor1B loci. Genomic sequence is depicted as a thin central line. Thick blocks indicate exons. Coding exons span the central line; exons encoding untranslated regions are fully below the central line. The positions of the T-DNA insertions are depicted with inverted triangles. (B) Reverse-Transcribed RNA-template Polymerase Chain Reactions (RT-PCR) on plants homozygous for both wild-type AtRaptor alleles (Col), the AtRaptor1A insertion allele (A-) or the AtRaptor1B insertion allele (B-), using primers spanning the AtRaptor1A insertion site, the AtRaptor1B insertion site, or control primers. Both AtRaptor insertion alleles abolish accumulation of the wild-type transcript from their locus.
Mentions: To gain insight into the function of the AtRaptor proteins, we searched for insertion alleles of each locus among the publicly available sequenced T-DNA insertion lines. Insertion mutant lines SALK_043920 and SALK_078159, with disruptions to the AtRaptor1A and AtRaptor1B loci, were obtained from the Arabidopsis Biological Resource Center (USA). Lines homozygous for each insertion (referred to as 1A -/- and 1B -/-, respectively) were identified via polymerase chain reaction (PCR), and RNA from floral buds of insertion homozygotes was used for reverse-transcriptase-PCR (RT-PCR) to assay for accumulation of wild-type transcripts from the disrupted locus. AtRaptor1A transcripts could not be detected in 1A -/- buds, but were detected in 1B -/- buds. AtRaptor1B transcripts were not detected in 1B -/- buds, but were detected in 1A -/- buds. Both transcripts were detected in wild-type Columbia (Col) buds (Fig. 2).

Bottom Line: AtRaptor transcripts accumulate in dividing and expanding cells and tissues.The data implicate the TOR signaling pathway, a major regulator of cell growth in yeast and metazoans, in the maintenance of growth from the shoot apical meristem in plants.These results provide insights into the ways in which TOR/Raptor signaling has been adapted to regulate plant growth and development, and indicate that in plants, as in other eukaryotes, there is some Raptor-independent TOR activity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Molecular Biology and Genetics, Cornell University, Ithaca, 14853, USA. ganderson@salk.edu

ABSTRACT

Background: Flowering plant development is wholly reliant on growth from meristems, which contain totipotent cells that give rise to all post-embryonic organs in the plant. Plants are uniquely able to alter their development throughout their lifespan through the generation of new organs in response to external signals. To identify genes that regulate meristem-based growth, we considered homologues of Raptor proteins, which regulate cell growth in response to nutrients in yeast and metazoans as part of a signaling complex with the target of rapamycin (TOR) kinase.

Results: We identified AtRaptor1A and AtRaptor1B, two loci predicted to encode Raptor proteins in Arabidopsis. Disruption of AtRaptor1B yields plants with a wide range of developmental defects: roots are thick and grow slowly, leaf initiation and bolting are delayed and the shoot inflorescence shows reduced apical dominance. AtRaptor1A AtRaptor1B double mutants show normal embryonic development but are unable to maintain post-embryonic meristem-driven growth. AtRaptor transcripts accumulate in dividing and expanding cells and tissues.

Conclusion: The data implicate the TOR signaling pathway, a major regulator of cell growth in yeast and metazoans, in the maintenance of growth from the shoot apical meristem in plants. These results provide insights into the ways in which TOR/Raptor signaling has been adapted to regulate plant growth and development, and indicate that in plants, as in other eukaryotes, there is some Raptor-independent TOR activity.

Show MeSH
Related in: MedlinePlus