Metal stress induces programmed cell death in aquatic fungi.
Aquatic hyphomycetes are a group of fungi that play a key role in organic matter turnover in both clean and metal-polluted streams. We examined the ability of Cu or Zn to induce programmed cell death (PCD) in three aquatic hyphomycete species through the evaluation of typical apoptotic markers, namely reactive oxygen species (ROS) accumulation, caspase-like activity, nuclear morphological alterations, and the occurrence of DNA strand breaks assessed by TUNEL assay. The exposure to both metals induced apoptotic events in all tested aquatic fungi. The most tolerant fungi either to Zn (Varicosporium elodeae) or Cu (Heliscussubmersus) exhibited higher levels of PCD markers, suggesting that PCD processes might be linked to fungal resistance/tolerance to metal stress. Moreover, different patterns of apoptotic markers were found, namely a PCD process independent of ROS accumulation in V. elodeae exposed to Cu, or independent of caspase-like activity in Flagellospora curta exposed to Zn, or even without the occurrence of DNA strand breaks in F. curta exposed to Cu. This suggests that a multiplicity of PCD pathways might be operating in aquatic hyphomycetes. The occurrence of a tightly regulated cell death pathway, such as PCD, in aquatic hyphomycetes under metal stress might be a part of the mechanisms underlying fungal acclimation in metal-polluted streams, because it would allow the rapid removal of unwanted or damaged cells sparing nutrients and space for the fittest ones.
Azevedo
Maria-Manuel
MM
Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
Almeida
Bruno
B
Ludovico
Paula
P
Cássio
Fernanda
F
D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects; D002843:Chromatin / Q000187:drug effects; D003300:Copper / Q000633:toxicity*; D053960:DNA Breaks / Q000187:drug effects; D020287:In Situ Nick-End Labeling; D003904:Mitosporic Fungi / Q000187:drug effects*; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015032:Zinc / Q000633:toxicity*
D002843:Chromatin; D017382:Reactive Oxygen Species; D014874:Water Pollutants, Chemical; D003300:Copper; D020169:Caspases; D015032:Zinc