Nuclei of symbiotic arbuscular mycorrhizal fungi as revealed by in vivo two-photon microscopy |
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Institution: | (1) Centre de Recherche en Biologie Forestière, Université Laval, Ste-Foy, Québec;(2) Applied and Engineering Physics, Cornell University, Ithaca, New York;(3) Present address: U.S. Department of Agriculture, Eastern Regional Research Center, ARS, 600 E. Mermaid Lane, 19038 Wyndmoor, PA, USA |
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Abstract: | Summary The present work reports the results obtained from in vivo studies on the distribution and behavior of nuclei of two arbuscular
mycorrhizal (AM) fungi growing in symbiosis with tomato root organ cultures (AM monoxenic cultures). Upon staining with 4′,6-diamidino-2-phenylindole
and two-photon microscopy (2PM) observations, symbiotic thick runner hyphae appeared mostly opaque to 2PM and did not reveal
nuclei within them; thin runner hyphae showed dimly stained nuclei along them, whereas nuclei were clearly visible within
the branches of the so-called branched absorbing structures. When visible, nuclei appeared anchored laterally at regular intervals
along the symbiotic AM extraradical hyphae. Other nuclei migrate through the hyphal central core; this migration occurs in
pulses. Simultaneous observations on different areas of extraradical AM mycelium revealed the existence of lysed compartments
along the fungal hyphae, containing nuclei remnants and/or chromatin masses. All these results give new insights in (i) the
differential permeability of AM hyphae in the symbiotic versus the asymbiotic state; (ii) the behavior and distribution of
nuclei along the symbiotic extraradical mycelium; (iii) the occurrence of ageing events within the AM fungal colony; and (iv)
the existence of “healing” mechanisms aiming to restrict the damage induced by such ageing or lytic events. An AM fungal strategy
for hyphal survival under adverse conditions is also suggested. |
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Keywords: | Gigaspora rosea Glomus intraradices 4′ 6-diamidino-2-phenylindole Extraradical mycelium Arbuscular-mycorrhizal monoxenic cultures Multiphoton microscopy |
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