Enhanced arsenate reduction by a CDC25-like tyrosine phosphatase explains increased phytochelatin accumulation in arsenate-tolerant Holcus lanatus

Decreased arsenate [As(V)] uptake is the major mechanism of naturally selected As(V) hypertolerance in plants. However, As(V)-hypertolerant ecotypes also show enhanced rates of phytochelatin (PC) accumulation, suggesting that improved sequestration might additionally contribute to the hypertolerance...

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Vydáno v:	The Plant journal : for cell and molecular biology Ročník 45; číslo 6; s. 917 - 929
Hlavní autoři:	Bleeker, Petra M, Hakvoort, Henk W.J, Bliek, Mattijs, Souer, Erik, Schat, Henk
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	Oxford, UK Oxford, UK : Blackwell Science Ltd 01.03.2006 Blackwell Science Ltd Blackwell Science Blackwell Publishing Ltd
Témata:	Amino Acid Sequence Amino acids Analysis of Variance Arabidopsis Arabidopsis - enzymology Arabidopsis - genetics Arabidopsis thaliana arsenate reductase arsenate tolerance Arsenates Arsenates - metabolism Arsenates - pharmacology Arsenic Arsenite Transporting ATPases Biological and medical sciences CDC25 cdc25 Phosphatases cdc25 Phosphatases - genetics cdc25 Phosphatases - metabolism complementary DNA Consensus Sequence DNA, Bacterial DNA, Bacterial - genetics DNA, Complementary DNA, Complementary - metabolism drug effects Ecotypes Enzymes enzymology Flowers & plants Fundamental and applied biological sciences. Psychology gene overexpression genes genetics Genotype & phenotype Glutathione Glutathione - metabolism Holcus Holcus - drug effects Holcus - enzymology Holcus - genetics Holcus lanatus Hypersensitivity Ion Pumps Ion Pumps - genetics Ion Pumps - metabolism Metabolism Molecular Sequence Data Multienzyme Complexes Multienzyme Complexes - genetics Multienzyme Complexes - metabolism Mutagenesis, Insertional mutants pharmacology Phenotype Phosphates phytochelatin synthase Phytochelatins Plant physiology and development Plant Proteins Plant Proteins - genetics Plant Proteins - metabolism Sequence Alignment toxicity transfer DNA tyrosine vacuolar transport Yeasts vacuolar transport Monocotyledones Root arsenate tolerance Hypersensitivity Tolerance arsenate reductase phytochelatin synthase Holcus lanatus Arabidopsis thaliana EC 2.3.2.15 Complementary DNA Gene Cruciferae Gramineae CDC25 Dicotyledones Angiospermae Spermatophyta Mutation
ISSN:	0960-7412, 1365-313X
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Popis
Shrnutí:	Decreased arsenate [As(V)] uptake is the major mechanism of naturally selected As(V) hypertolerance in plants. However, As(V)-hypertolerant ecotypes also show enhanced rates of phytochelatin (PC) accumulation, suggesting that improved sequestration might additionally contribute to the hypertolerance phenotype. Here, we show that enhanced PC-based sequestration in As(V)-hypertolerant Holcus lanatus is not due to an enhanced capacity for PC synthesis as such, but to increased As(V) reductase activity. Vacuolar transport of arsenite-thiol complexes was equal in both ecotypes. Based on homology with the yeast As(V) reductase, Acr2p, we identified a Cdc25-like plant candidate, HlAsr, and confirmed the As(V) reductase activity of both HlAsr and the homologous protein from Arabidopsis thaliana. The gene appeared to be As(V)-inducible and its expression was enhanced in the As(V)-hypertolerant H. lanatus ecotype, compared with the non-tolerant ecotype. Homologous ectopic overexpression of the AtASR cDNA in A. thaliana produced a dual phenotype. It improved tolerance to mildly toxic levels of As(V) exposure, but caused hypersensitivity to more toxic levels. Arabidopsis asr T-DNA mutants showed increased As(V) sensitivity at low exposure levels and enhanced arsenic retention in the root. It is argued that, next to decreased uptake, enhanced expression of HlASR might act as an additional determinant of As(V) hypertolerance and As transport in H. lanatus.
Bibliografie:	http://dx.doi.org/10.1111/j.1365-313X.2005.02651.x Present address: Rothamsted Research, Crop Performance and Improvement Division, Harpenden, AL5 2JQ, UK. Present address: Institute for Molecular and Cellular Biology, Department of Genetics, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands. SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 14 ObjectType-Article-1 ObjectType-Feature-2 content type line 23
ISSN:	0960-7412 1365-313X
DOI:	10.1111/j.1365-313x.2005.02651.x