PLANT PHYSIOLOGY , Vol 109, Issue 3 871-878, Copyright © 1995 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Copper-Sensitive Mutant of Arabidopsis thaliana
C. van Vliet, C. R. Andersen and C. S. Cobbett
Department of Genetics, The University of Melbourne, Parkville, Australia 3052
A Cu-sensitive mutant, cup1-1, of Arabidopsis thaliana has a pattern of
heavy-metal sensitivity different from that of the cad1 and cad2 mutants,
which are deficient in phytochelatin biosynthesis. The latter are
significantly sensitive to Cd and Hg and only slightly sensitive to Cu,
whereas the cup1-1 mutant is significantly sensitive to Cu, slightly
sensitive to Cd, and not more sensitive to Hg, compared to the wild type.
Genetic analysis has shown that the sensitive phenotype is recessive to the
wild type and segregates as a single Mendelian locus, which has been mapped
to chromosome 1. Genetic and biochemical studies demonstrate that the
cup1-1 mutant is not affected in phytochelatin biosynthesis or function.
The sensitive phenotype of the cup1-1 mutant is associated with, and
probably due to, increased accumulation of higher levels of Cd and Cu
compared with the wild type. Consistent with this, a Cu-inducible,
root-specific metallothionein gene, MT2a, is expressed in cup1-1 roots
under conditions in which it is not expressed in the wild type.
Undifferentiated cup1-1 callus tissue did not show the Cu-sensitive
phenotype, suggesting that the mutant phenotype, in contrast to cad1 and
cad2, is not expressed at the cellular level.
