title: ATR regulates a G2-phase cell-cycle checkpoint in Arabidopsis thaliana.
abstract: Ataxia telangiectasia-mutated and Rad3-related (ATR) plays a central role in cell-cycle regulation, transmitting DNA damage signals to downstream effectors of cell-cycle progression. In animals, ATR is an essential gene. Here, we find that Arabidopsis (Arabidopsis thaliana) atr-/- mutants were viable, fertile, and phenotypically wild-type in the absence of exogenous DNA damaging agents but exhibit altered expression of AtRNR1 (ribonucleotide reductase large subunit) and alteration of some damage-induced cell-cycle checkpoints. atr mutants were hypersensitive to hydroxyurea (HU), aphidicolin, and UV-B light but only mildly sensitive to gamma-radiation. G2 arrest was observed in response to gamma-irradiation in both wild-type and atr plants, albeit with slightly different kinetics, suggesting that ATR plays a secondary role in response to double-strand breaks. G2 arrest also was observed in wild-type plants in response to aphidicolin but was defective in atr mutants, resulting in compaction of nuclei and subsequent cell death. By contrast, HU-treated wild-type and atr plants arrested in G1 and showed no obvious signs of cell death. We propose that, in plants, HU invokes a novel checkpoint responsive to low levels of deoxynucleotide triphosphates. These results demonstrate the important role of cell-cycle checkpoints in the ability of plant cells to sense and cope with problems associated with DNA replication.
authors.affiliation: Section of Plant Biology, University of California, Davis, California 95616, USA. kmculligan@ucdavis.edu
authors.forename: Kevin
authors.initials: K
authors.lastname: Culligan
authors.forename: Alain
authors.initials: A
authors.lastname: Tissier
authors.forename: Anne
authors.initials: A
authors.lastname: Britt
mesh_terms: D016590:Aphidicolin / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics*; D004261:DNA Replication / Q000187:drug effects / Q000528:radiation effects; D017353:Gene Deletion; D006918:Hydroxyurea / Q000494:pharmacology; D008969:Molecular Sequence Data; D010641:Phenotype; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D016590:Aphidicolin; C576892:ATR protein, Arabidopsis; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D006918:Hydroxyurea