An extracellular transglutaminase is required for apple pollen tube growth

Alessia Di Sandro, Stefano Del Duca, Elisabetta Verderio, Alan J. Hargreaves, Alessandra Scarpellini, Giampiero Cai, Mauro Cresti, Claudia Faleri, Rosa A. Iorio, Shigehisa Hirose, Yutaka Furutani, Ian G.C. Coutts, Martin Griffin, Philip L.R. Bonner, Donatella Serafini-Fracassini

Research output: Contribution to journalArticlepeer-review


An extracellular form of the calcium-dependent protein-cross-linking enzyme TGase (transglutaminase) was demonstrated to be involved in the apical growth of Malus domestica pollen tube. Apple pollen TGase and its substrates were co-localized within aggregates on the pollen tube surface, as determined by indirect immunofluorescence staining and the in situ cross-linking of fluorescently labelled substrates. TGase-specific inhibitors and an anti-TGase monoclonal antibody blocked pollen tube growth, whereas incorporation of a recombinant fluorescent mammalian TGase substrate (histidine-tagged green fluorescent protein: His6-Xpr-GFP) into the growing tube wall enhanced tube length and germination, consistent with a role of TGase as a modulator of cell wall building and strengthening. The secreted pollen TGase catalysed the cross-linking of both PAs (polyamines) into proteins (released by the pollen tube) and His6-Xpr-GFP into endogenous or exogenously added substrates. A similar distribution of TGase activity was observed in planta on pollen tubes germinating inside the style, consistent with a possible additional role for TGase in the interaction between the pollen tube and the style during fertilization.
Original languageEnglish
Pages (from-to)261-271
Number of pages11
JournalBiochemical Journal
Issue number2
Publication statusPublished - 5 May 2010


  • extracellular space
  • germination
  • green fluorescent proteins
  • immunohistochemistry
  • malus
  • biological models
  • genetically modified plants
  • pollen tube
  • recombinant proteins
  • substrate specificity
  • transglutaminases


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