, Volume 220, Issue 6, pp 889–899 | Cite as

Differential location of α-expansin proteins during the accommodation of root cells to an arbuscular mycorrhizal fungus

  • R. Balestrini
  • D. J. Cosgrove
  • P. BonfanteEmail author
Original Article


α-Expansins are extracellular proteins that increase plant cell-wall extensibility. We analysed their pattern of expression in cucumber roots in the presence and in the absence of the mycorrhizal fungus, Glomus versiforme. The distribution of α-expansins was investigated by use of two polyclonal antibodies (anti-EXPA1 and anti-EXPA2, prepared against two different cucumber α-expansins) in immunoblotting, immunofluorescence, and immunogold experiments. Immunoblot results indicate the presence of a 30-kDa band specific for mycorrhizal roots. The two antibodies identify antigens with a different distribution in mycorrhizal roots: anti-EXPA1 labels the interface zone, but the plant cell walls only weakly. By contrast, the anti-EXPA2 labels only the plant cell walls. In order to understand the potential role of α-expansins during the accommodation of the fungus inside root cells, we prepared semi-thin sections to measure the size of cortical cells and the thickness of cortical cell walls in mycorrhizal and non-mycorrhizal root. Mycorrhizal cortical cells were significantly larger than non-mycorrhizal cells and had thicker cell walls. In double-labelling experiments with cellobiohydrolase–gold complex, we observed that cellulose was co-localized with α-expansins. Taken together, the results demonstrate that α-expansins are more abundant in the cucumber cell walls upon mycorrhizal infection; we propose that these wall-loosening proteins are directly involved in the accommodation of the fungus by infected cortical cells.


Arbuscular mycorrhizae Expansin Cell expansion Cellulose Cell wall 



Arbuscular mycorrhiza(l)








Xyloglucan endotransglycosylase



This research was funded by the Italian FIRB Project (RBNE01KZE7), by IPP-CNR and CEBIOVEM (D.M. 193/2003) grants. Confocal and electron microscope facilities were available at LMA-Dipartimento di Biologia Vegetale dell’Università di Torino.


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  1. 1.Istituto per la Protezione delle Piante del CNRSezione di Micologia and Dipartimento di Biologia Vegetale dell’UniversitàTurinItaly
  2. 2.Department of BiologyPennsylvania State UniversityUniversity ParkUSA

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