Aluminum-dependent root-growth inhibition in Arabidopsis results from AtATR-regulated cell-cycle arrest.
Aluminum (Al) toxicity is a global problem severely limiting agricultural productivity in acid-soil regions comprising upwards of 50% of the world's arable land [1, 2]. Although Al-exclusion mechanisms have been intensively studied [3-9], little is known about tolerance to internalized Al, which is predicted to be mechanistically complex because of the plethora of predicted cellular targets for Al(3+)[2, 10]. An Arabidopsis mutant with Al hypersensitivity, als3-1, was found to represent a lesion in a phloem and root-tip-localized factor similar to the bacterial ABC transporter ybbm, with ALS3 likely responsible for Al transfer from roots to less-sensitive tissues [10-12]. To identify mutations that enhance mechanisms of Al resistance or tolerance, a suppressor screen for mutants that mask the Al hypersensitivity of als3-1 was performed [13]. Two allelic suppressors conferring increased Al tolerance were found to represent dominant-negative mutations in a factor required for monitoring DNA integrity, AtATR[14-17]. From this work, Al-dependent root-growth inhibition primarily arises from DNA damage coupled with AtATR-controlled blockage of cell-cycle progression and terminal differentiation because of loss of the root-quiescent center, with mutations that prevent response to this damage resulting in quiescent-center maintenance and sustained vigorous growth in an Al-toxic environment.
Department of Biochemistry, University of California, Riverside, California 92521, USA.
Megan A
MA
Rounds
Paul B
PB
Larsen
D000535:Aluminum / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D018517:Plant Roots / Q000254:growth & development*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D000535:Aluminum; C576892:ATR protein, Arabidopsis; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases