Ectomycorrhizal fungi are able to ameliorate heavy metal stress to host trees in polluted soils. Their sensitivity or tolerance to heavy metals is usually examined based on growth and proliferation on heavy metal amended media. However, there are no data on cellular effects of heavy metals and detoxification in live cells of these fungi. Organelle morphology has recently been recognized as an indication of cellular health and its changes can be used to assess cytotoxicity. The aim of this study was, therefore, to investigate short term effects of common heavy metal pollutants, Zn2+ and Ni2+ on the morphology of vacuoles, mitochondria and microtubules in hyphal tip cells of two Paxillus involutus strains. Vacuoles, mitochondria and microtubules were labeled with Oregon Green?? 488 carboxylic acid diacetate, 3,3'-dihexyloxacarbocyanine iodide ((DiOC6(3)) and anti-??- tubulin antibodies, respectively. They were treated with 0-1 mmol L-1 NiSO4 or 0-100 mmol L-1 ZnSO4 or K2SO4 (SO4 2- control) and examined by fluorescence microscopy. Vacuoles and mitochondria in untreated hyphal tip cells of strain P2 which originated from a heavy metal-rich soil were motile and tubular forming networks. Exposure to the metals caused tubular vacuole thickening and vesiculation as well as fragmentation of tubular mitochondria in living hyphal tip cells. The highest K2SO4 concentration also had severe effects on mitochondria. These effects were metal, concentration and exposure time dependent. NiSO4 caused these effects at a hundred fold lower concentration than ZnSO4 and induced severe microtubule disruption. Vacuole tubularity recovered after removal of the metal solutions depending on the metal, concentration and exposure time. Mitochondrial tubularity recovered to pretreatment morphology in a shorter time and even during exposure to the highest metal concentration. Vacuoles of strain P46 which originated from a non-polluted soil were pleomorphic, but mainly spherical with occasional tubular interconnections. The vacuoles were too sensitive to UV light exposure required for fluorescence microscopy to investigate their response to heavy metals. The mitochondrial network and microtubules resembled those of strain P2. The highest ZnSO4 and NiSO4 concentrations caused similar trends in response of mitochondria and microtubules of the two strains. However, mitochondria of strain P46 were less sensitive at lower metal concentrations. The highest K2SO4 concentration had more severe effects on mitochondria of strain P46 than in strain P2 from which tubularity was not recovered. This investigation is the first to reveal that heavy metals affect organelle morphology in two strains of an ectomycorrhizal fungus. Nickel effects on the organelles are likely to result from microtubule disruption. Metal induced mitochondrial fragmentation is possibly an apoptotic response and the recovery of tubular organelle networks suggests cellular detoxification.
| Identifer | oai:union.ndltd.org:ADTP/234238 |
| Date | January 2005 |
| Creators | Tuszynska, Sandra, School of Biotechnology & Biomolecular Science, UNSW |
| Publisher | Awarded by:University of New South Wales. School of Biotechnology and Biomolecular Science |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Sandra Tuszynska, http://unsworks.unsw.edu.au/copyright |
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