title: The Arabidopsis cell cycle checkpoint regulators TANMEI/ALT2 and ATR mediate the active process of aluminum-dependent root growth inhibition.
abstract: Aluminum (Al) toxicity is a global issue that severely limits root growth in acidic soils. Isolation of suppressors of the Arabidopsis thaliana Al-hypersensitive mutant, als3-1, resulted in identification of a cell cycle checkpoint factor, ALUMINUM TOLERANT2 (ALT2), which monitors and responds to DNA damage. ALT2 is required for active stoppage of root growth after Al exposure, because alt2 loss-of-function mutants fail to halt root growth after Al exposure, do not accumulate CyclinB1;1 in the root tip, and fail to force differentiation of the quiescent center. Thus, alt2-1 mutants are highly tolerant of Al levels that are severely inhibitory to the wild type. The alt2-1 allele is a loss-of-function mutation in a protein containing a putative DDB1-binding WD40 motif, previously identified as TANMEI, which is required for assessment of DNA integrity, including monitoring of DNA crosslinks. alt2-1 and atr loss-of-function mutants, the latter of which affects the cell cycle checkpoint ATAXIA TELANGIECTASIA-MUTATED AND RAD3-RELATED, are severely sensitive to DNA crosslinking agents and have increased Al tolerance. These results suggest that Al likely acts as a DNA-damaging agent in vivo and that Al-dependent root growth inhibition, in part, arises from detection of and response to this damage by TANMEI/ALT2 and ATR, both of which actively halt cell cycle progression and force differentiation of the quiescent center.
authors.affiliation: Department of Biochemistry, University of California, Riverside, California 92521, USA.
authors.forename: Cynthia D
authors.initials: CD
authors.lastname: Nezames
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Sjogren
authors.forename: Jesus F
authors.initials: JF
authors.lastname: Barajas
authors.forename: Paul B
authors.initials: PB
authors.lastname: Larsen
mesh_terms: D000535:Aluminum / Q000494:pharmacology*; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D064007:Ataxia Telangiectasia Mutated Proteins; D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004249:DNA Damage; D005816:Genetic Complementation Test; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; C507146:TAN protein, Arabidopsis; D000535:Aluminum; C576892:ATR protein, Arabidopsis; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases