Anti-tubulin antibodies locate the blepharoplast during spermatogenesis in the fern Platyzoma microphyllum R.Br.: a correlated immunofluorescence and electron-microscopic study.

The discovery that the monoclonal anti-tubulin antibody YOL 1/34 recognizes a microtubule organizing centre, the blepharoplast (which arises de novo during the latter stages of spermatogenesis in the fern, Platyzoma microphyllum), has enabled us to follow it and associated microtubules throughout most of its ontogeny. By correlating electron-microscopic and immunofluorescence observations, YOL 1/34 is seen to stain the blepharoplast uniformly at a time when no microtubules are present within the organelle. Later, staining becomes intense at the surface, concomitant with the re-location of cylindrical channels to the periphery of the blepharoplast. During anaphase of the ultimate division of the spermatid mother cell the blepharoplast moves to the spindle poles and sharpens the otherwise barrel-shaped mitotic apparatus. Prior to this stage the blepharoplast is, however, off-centre and at variable positions around the poles. Later still, in the differentiating spermatids, the blepharoplast is the focus for radiating cytoplasmic microtubules that abut directly onto the electron-dense organelle, penetrating the ribosome-free halo. The three main conclusions are: that tubulin in a pre-microtubular form is associated with the cylindrical channels that arise de novo within the previously amorphous blepharoplast and act as a template in basal body formation; that the late appearance of the blepharoplast as a focus for the spindle poles during the final mitosis provides strong argument against its functioning during spindle pole initiation (despite its ability to sharpen the poles at anaphase); that the blepharoplast does seem to act as a microtubule organizing centre in the mitotically quiescent spermatid.