An extracellular transglutaminase is required for apple pollen tube growth

Alessia Di Sandro , Stefano del Duca , Elisabetta Am Verderio , Alan Jeffrey Hargreaves , Alessandra Scarpellini , Giampiero Cai , Mauro Cresti , Claudia Faleri , Rosa Anna Iorio , Shigehisa Hirose , Yutaka Furutani , Ian G.C. Coutts , Martin Griffin , Philip L.R. Bonner , Donatella Serafini (1)

1 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna

An extracellular form of the Ca2+-dependent protein-cross-linking enzyme transglutaminase (TGase) was demonstrated to be involved in the apical growth of Malus domestica pollen tube. Apple pollen transglutaminase and its substrates were co-localized within aggregates on the pollen tube surface, as determined by indirect immuno-fluorescence staining and the in situ cross-linking of fluorescently labeled substrates. Transglutaminase-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 modulator of cell wall building and strengthening. The secreted pollen TGase catalyzed the cross-linking of both polyamines (PAs) 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.

Mots clés: Life Sciences

Alessia Di Sandro, Stefano del Duca, Elisabetta Am Verderio, Alan Jeffrey Hargreaves, Alessandra Scarpellini, et al.. An extracellular transglutaminase is required for apple pollen tube growth. Biochemical Journal, 2010, 429 (2), pp.261-271. ⟨10.1042/BJ20100291⟩. ⟨hal-00495492⟩