Ni2+ induces changes in the morphology of vacuoles, mitochondria and microtubules in Paxillus involutus cells

Abstract

Summary• Organelles of ectomycorrhizal fungi are known to respond to changes in the extracellular environment. The response of vacuoles, mitochondria and microtubules to short-term nickel (Ni 2+ ) exposure were investigated in hyphal tip cells of a Paxillus involutus from a heavy metal-rich soil.• Vacuoles, mitochondria and microtubules were labelled with Oregon Green ® 488 carboxylic acid diacetate, 3,3 ′ -dihexyloxacarbocyanine iodide (DiOC 6 (3)) and anti-α -tubulin antibodies, respectively; hyphae were treated with NiSO 4 in the range of 0-1 mmol l − 1 and examined microscopically.• Untreated hyphal tip cells contained tubular vacuole and mitochondrial networks. Ni 2+ caused loss of organelle tubularity and severe microtubule disruption that were exposure-time and concentration dependent. Fine tubular vacuoles thickened and eventually became spherical in some hyphae, tubular mitochondria fragmented and microtubules shortened and aggregated into patches in most hyphae. Tubular vacuoles reformed on NiSO 4 removal and tubular mitochondria in the presence of NiSO 4 suggesting cellular detoxification.• These results demonstrate that Ni 2+ induces changes in organelle and microtubule morphology. Recovery of tubular organelles to pretreatment morphology after Ni 2+ exposure suggests cellular detoxification of the metal ion.

Identification of vacuole defects in fungi

“…The chloromethyl group reacts with thiols such as glutathione producing fluorescent conjugates that are membrane impermeable and so are retained within the vacuole lumen (Haugland, 1995;Cole et al, 1997). Similarly, a set of fluorescent vacuole markers based on 6-carboxyfluorescein diacetate (CFDA) and its derivatives (CDCFDA, 5-[and 6-] carboxy-2′, 7′-dichlorofluorescein diacetate, cDFFDA, and Oregon Green 488 carboxylic acid diacetate) have been used to visualise vacuoles in a range of fungi such as C. albicans (Veses et al, 2009b), P. tinctorius (Hyde et al, 2002), Paxillus involutus (Tuszynska, 2006), P. velutina (Darrah et al, 2006;Fricker et al, 2008;Zhuang et al, 2009), A. nidulans (Peñalva, 2005), Gigaspora margarita (Saito et al, 2004), S. cerevisiae (Shiflett et al, 2004), U. maydis (Torralba and Heath, 2002) and C. neoformans (Harrison et al, 2002). They work by the same principle as CMAC, and are colourless non-polar compounds which readily diffuse across cell membranes.…”

Changes in vacuolar and mitochondrial motility and tubularity in response to zinc in a Paxillus involutus isolate from a zinc-rich soil

“…1A and B) already described in Tuszynska (2006). Fine tubular vacuoles were most abundant within the apex of the tip cell.…”

“…Tubular mitochondria extended along the hyphae and small mitochondrial fragments often travelled along a hypha to fuse with other mitochondria. This morphology was deWned as "tubular mitochondria", already described in Tuszynska (2006). Zinc sulphate caused tubular mitochondria to become shorter and swollen, until most appeared as Xuorescent spots of diVerent sizes (Figs.…”

“…Since latrunculin did not cause this eVect, it was explained as being due to microtubules. Nickel which has a very similar eVect on vacuoles and mitochondria as that induced here by Zn 2+ has recently been shown to severely disrupt microtubules (Tuszynska, 2006). It is certainly feasible that zinc caused a similar eVect by disruption of the microtubules and this requires further testing.…”

“…Recently, nickel has been found to induce a very similar organelle response (Tuszynska, 2006). The lack of eVect of K 2 SO 4 on the vacuole system indicates that the eVects of ZnSO 4 on vacuoles are caused by Zn 2+ , not SO 4 2¡ .…”