Figure 6

Extensins in pistils of Malus x domestica, unpollinated (A,B,E,F,I) and pollinated (C,D,G,H,J) flowers; at the stigma (A-D), middle of the style (E-H), and the style base (I-J). (A) Cell walls of the transmitting tissue stained for cellulose, and (B) intercellular spaces immunolocalized for extensin epitopes (fluorescent green) in the upper stylar transmitting tissue two days after anthesis (2DAA). (C) Transmitting tissue stained cell walls and pollen tubes (arrows) two days after pollination (2DAP). (D) Extensin epitopes decreased detectability in the extracellular spaces, particularly in the areas traversed by the pollen tubes (stars). (E) Cells of the transmitting tissue in an unpollinated style three days after anthesis (3DAA). (F) Same section showed extensin epitopes recognized by JIM11 mAb in the extracellular domains of the dense cytoplasmic elongated cells. (G) Pollen tube (arrows) traversing the extracelluar matrix of the transmitting tissue three days after pollination (3DAP). (H) Same section immunolocalized for JIM11 extensin epitopes in the extracellular matrix showing conspicuous contact with pollen tube walls. (I) Overlapped images of calcofluor and JIM11 extensin epitopes; extensins fill intercellular spaces at the style base three days after anthesis (3DAA). (G) Same area at the style base devoid of extensins (asterisks) following pollen tubes passage. Style 4 μm longitudinal (A-H) or transversal (I-J) sections stained with Calcofluor white (A, C, E, G), immunolocalized for extensin epitopes showing FITC labelling in fluorescent green (B, D, F, H), and merged images of calcofluor white and FITC signalling (I-J). ct, cortical tissue; pg, pollen grain; st, stigmatoid tissue; tt, transmitting tissue. (A-D) scale bars: 50μm; (E-J) scale bars: 10 μm.