Foliar-applied glutathione activates zinc transport from roots to shoots in oilseed rape.

Glutathione is a tripeptide involved in diverse aspects of plant metabolism. We investigated how the reduced form of glutathione, GSH, applied site-specifically to plants, affects zinc (Zn) distribution and behavior in oilseed rape plants (Brassica napus) cultured hydroponically. Foliar-applied GSH significantly increased the Zn content in shoots and the root-to-shoot Zn translocation ratio; furthermore, this treatment raised the Zn concentration in the cytosol of root cells and substantially enhanced Zn xylem loading. Notably, microarray analysis revealed that the gene encoding pectin methylesterase was upregulated in roots following foliar GSH treatment. We conclude that certain physiological signals triggered in response to foliar-applied GSH were transported via sieve tubes and functioned in root cells, which, in turn, increased Zn availability in roots by releasing Zn from their cell wall. Consequently, root-to-shoot translocation of Zn was activated and Zn accumulation in the shoot was markedly increased.