Fig. 3. Plant Spc98p and -tubulin localization at the surface of isolated tobacco BY-2 nuclei after in vitro MT nucleation. (A) Mid-section of a confocal z-stack labeled with anti-Spc98pB/Alexa 488. (B) Top section at the surface of the same nucleus labeled with anti--tubulin/Alexa 568. (C) Merged mid-section showing the perinuclear sites of MT nucleation. (D) Midsection of a nucleus revealed with anti--tubulin/Alexa 488. (E) Top-section at the surface of the same nucleus labeled with anti--tubulin/Alexa568. (F) Merged mid-section using a Zeiss LSM 510 microscope. Insets, Nomarski images of the isolated nuclei. (G) Inhibition of MT nucleation by preincubation with anti--tubulin antibodies. Merged projection of an entire nucleus. No MTs are polymerized. (H) Inhibition by anti-Spc98pB antibodies: a few short MT remnants are observed at the surface of the nucleus in this merged projection, but no MT nucleation was observed. (I) Following a competition assay for 1 hour with preincubation using anti-Spc98pB antibodies and Spc98pB peptide, nucleation was not inhibited. Bar, 10 µm.