Document Detail

Arabidopsis thaliana deficient in two chloroplast ascorbate peroxidases shows accelerated light-induced necrosis when levels of cellular ascorbate are low.
MedLine Citation:
PMID:  17823777     Owner:  NLM     Status:  MEDLINE    
Arabidopsis chloroplasts have a multi-layered defense against hydrogen peroxide (H(2)O(2)) that includes a stromal and thylakoid ascorbate peroxidase (sAPX and tAPX). Single and double null mutants in SAPX and TAPX (sapx and tapx) were each crossed with ascorbate deficient vtc2. The single, double and triple mutants did not show visual light stress phenotypes when grown at control or high light intensities (CL and HL; 120 and 1,000 micromol photons m(-2) s(-1)). Upon shift from CL to HL, mesophyll of expanded leaves of the triple mutant bleached within hours, with exclusion of the major vein areas; this contrasts to reported patterns of cell death under ozone treatment and calatase deficiency. tapx-vtc2 and sapx-vtc2, but not tapx-sapx or single mutants, showed limited bleaching. Bleaching and necrosis were accompanied by accumulation of H(2)O(2). Cellular concentrations of alpha-tocopherol, ascorbate and glutathione showed dramatic increase in response to HL in all eight genotypes and the four vtc2 genotypes accumulated more glutathione under CL than the others. Transcript analysis of other ROS responsive genes in vtc2 and the triple mutant showed up to 20-fold induction after transition to HL, generally irrespective of genotype. We conclude that chloroplast APX proteins in Arabidopsis can be effectively compensated by other endogenous H(2)O(2) detoxification systems, but that low cellular ascorbate levels in absence of chloroplast APX activity are detrimental to the cell during excess light.
Lisa Giacomelli; Antonio Masi; Daniel R Ripoll; Mi Ja Lee; Klaas J van Wijk
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2007-09-07
Journal Detail:
Title:  Plant molecular biology     Volume:  65     ISSN:  0167-4412     ISO Abbreviation:  Plant Mol. Biol.     Publication Date:  2007 Nov 
Date Detail:
Created Date:  2007-10-23     Completed Date:  2008-01-16     Revised Date:  2011-01-25    
Medline Journal Info:
Nlm Unique ID:  9106343     Medline TA:  Plant Mol Biol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  627-44     Citation Subset:  IM    
Department of Plant Biology, Cornell University, Emerson Hall 332, Tower Road, Ithaca, NY 14853, USA.
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MeSH Terms
Arabidopsis / enzymology,  physiology,  radiation effects*
Arabidopsis Proteins / genetics*
Ascorbic Acid / metabolism*
Chloroplasts / enzymology*
Gene Expression Regulation, Plant
Hydrogen Peroxide / metabolism
Peroxidases / genetics*
Plastids / genetics,  metabolism
Reactive Oxygen Species / metabolism
Reg. No./Substance:
0/Arabidopsis Proteins; 0/Reactive Oxygen Species; 50-81-7/Ascorbic Acid; 7722-84-1/Hydrogen Peroxide; EC 1.11.1.-/Peroxidases; EC peroxidase

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