Plant Physiology Preview
Published on March 10, 2006; 10.1104/pp.106.077982
Received January 27, 2006
Returned for revision February 15, 2006
Accepted February 22, 2006
Maturation of Arabidopsis seeds is dependent on glutathione biosynthesis within the embryo
Narelle G. Cairns , Maciej Pasternak , Andreas Wachter , Christopher S. Cobbett , and Andreas J. Meyer *
Department of Genetics, The University of Melbourne, 3010, Australia
Heidelberg Institute of Plant Sciences, University of Heidelberg, Im Neuenheimer Feld 360, D-69120 Heidelberg, Germany
* Corresponding author; email: ameyer{at}hip.uni-hd.de.
Glutathione (GSH) has been implicated in maintaining the cell-cycle within plant meristems and protection of proteins during seed dehydration. To assess the role of GSH during development of Arabidopsis (Arabidopsis thaliana (L.) Heynh.) embryos we characterized T-DNA insertion mutants of GSH1, encoding the first enzyme of GSH biosynthesis,  -glutamylcysteine synthetase. These gsh1 mutants confer a recessive embryo lethal phenotype, in contrast to the previously described GSH1 mutant, rml1, which is able to germinate but is deficient in post-embryonic root development. Homozygous mutant embryos show normal morphogenesis until the seed maturation stage. The only visible phenotype in comparison to wild-type was progressive bleaching of the mutant embryos from the torpedo stage onwards. Confocal imaging of GSH in isolated mutant and wild-type embryos after fluorescent labeling with monochlorobimane (MCB) detected residual amounts of GSH in rml1 embryos. In contrast, gsh1 T-DNA insertion mutant embryos could not be labeled with MCB from torpedo stage onwards indicating the absence of GSH. By using HPLC, however, GSH was detected in extracts of mutant ovules and imaging of intact ovules revealed a high concentration of GSH in the funiculus, within the phloem unloading zone and in the outer integument. The observation of high GSH in the funiculus is consistent with a high GSH1-promoter::GUS reporter activity in this tissue. Development of mutant embryos could be partially rescued by exogenous GSH in vitro. These data show that at least a small amount of GSH synthesized autonomously within the developing embryo is essential for embryo development and proper seed maturation.
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