Cu,Zn superoxide dismutase and zinc stress in the metal-tolerant ericoid mycorrhizal fungusOidiodendron maiusZn

Abstract

The sequence encoding a superoxide dismutase (SOD) was isolated from the cDNA library of a zinc-tolerant strain of the ericoid mycorrhizal fungus Oidiodendron maius, grown under zinc-stress conditions. Sequence homology to other SODs strongly suggests that it is a copper- and zinc-containing SOD. Functional complementation assays showed that the gene confers increased tolerance to zinc and copper stress to a Cu,ZnSOD-defective yeast mutant. Monitoring of transcript and protein levels following zinc stress suggests that OmSOD1 expression is controlled at the transcriptional level. The OmSod1 protein was found both in the cell extract and in the growth medium of viable fungal cultures. This is the first characterization of an extracellular Cu,ZnSOD in a mycorrhizal fungus. In nature, the presence of OmSod1 in the extracellular environment may also extend the protective role of this enzyme to the plant symbiont. This may be of particular interest from the perspective of using mycorrhizal fungi in bioremediation programmes.

Colonization with arbuscular mycorrhizal fungus affects growth, drought tolerance and expression of stress-responsive genes in Poncirus trifoliata

“…As alluded to earlier, SOD and POD are two important enzymes involved in the elimination of superoxide anion and H 2 O 2 , respectively. Our data show that higher activities of SOD and POD were scored in the mycorrhizal plants than in the NAM plants, consistent with several other reports indicating that the activity of antioxidant enzymes was induced by AMF inoculation (Vallino et al 2009;Bressano et al 2010;Latef and He 2011). Our data and those of others seem to suggest that the AM symbiosis might provoke a more powerful ROS scavenging system in host plants and thus reduce destruction of biomolecules at the cellular level.…”

“…Plants have evolved a set of defense machinery to remove the ROS so as to ameliorate the oxidative stress for cellular survival. Under stresses, activation of the antioxidant enzymes has been shown to be a common consequence, among which SOD (superoxide dismutase) and POD (peroxidase) play key roles in removal of ROS produced under stresses, as has been shown elsewhere (Llorente et al 2002;Vallino et al 2009;Miller et al 2010;Shi et al 2010).…”

Genome-wide inventory of metal homeostasis-related gene products including a functional phytochelatin synthase in the hypogeous mycorrhizal fungus Tuber melanosporum

“…(Brown and Wilkins, 1985) and Pinus sylvestris (Adriaensen et al, 2004). Similar observations have been reported for other symbiotic associations, such as those established by the ericoid mycorrhizal fungus Oidiodendron maius, where increased zinc tolerance of the host plant (Vaccinium myrtillus) appears to rely, at least in part, on the Zn-dependent production of a fungal extracellular superoxide dismutase (Vallino et al, 2009). Mycorrhizal fungi may thus play an important dual role in metal homeostasis: scavenging of metal micronutrients and their supply to the host plant; detoxification of excess essential metals and nonessential metal ions as well.…”

Characterization of a CuZn superoxide dismutase gene in the arbuscular mycorrhizal fungus Glomus intraradices

“…Induction of SODs by the superoxide generators menadione and paraquat, as well as by heavy metals has been reported in other fungi (Culotta et al 1995;Ott et al 2002;Vallino et al 2009). Accumulation of ROS and induction of an oxidative damage to the fungal membranes when the extraradical mycelia of G. intraradices were exposed to either paraquat or copper have been recently reported (González-Guerrero et al 2007; Benabdellah et al 2009).…”