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

R. Balestrini, Daniel J. Cosgrove, P. Bonfante

Research output: Contribution to journalArticle

54 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)889-899
Number of pages11
JournalPlanta
Volume220
Issue number6
DOIs
StatePublished - Apr 1 2005

All Science Journal Classification (ASJC) codes

  • Genetics
  • Plant Science

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