GintMT1 encodes a functional metallothionein in Glomus intraradices that responds to oxidative stress

A full-length metallothionein (MT) gene (GintMT1) was isolated from Glomus intraradices extra-radical mycelium. This is the first MT gene reported in the genus Glomus; third in the Glomeromycota. Functional analysis of GintMT1 in a MT-defective Saccharomyces cerevisiae strain indicates that it encodes a functional MT. Gene expression analyses revealed that the transcript levels of GhttMT1 were elevated in mycelia treated with 5 mM Cu or paraquat but inhibited in mycelia treated with 50 RM Cu or 450 mu M Cd. The elevated expression of GintMT1 in the 5 mM Cu-treated mycelia together with the ability of GintMT1 to provide tolerance to a Cu-sensitive yeast suggests that GintMT1 might afford protection against Cu. Induction of GintMT1 expression by paraquat and 5 mM Cu, treatments that also produced an oxidative damage to the fungal membranes, suggests that GintMT1 may play a role in the regulation of the redox status of the extraradical mycelium of G. intraradices.