Some retrospectives on early studies of plant microtubules.

We pay tribute to the seminal paper 'A microtubule in plant cell fine structure' by Myron C. Ledbetter and Keith R. Porter (1963) by summarizing the very limited knowledge of plant cell ultrastructure that we had prior to that publication, and, by way of our three retrospective accounts, show how this paper stimulated and influenced subsequent research on plant microtubules.

Precocious (pre-anaphase) cleavage furrows in Mesostoma spermatocytes.

It generally is assumed that cleavage furrows start ingression at anaphase, but this is not always true. Cleavage furrows are initiated during prometaphase in spermatocytes of the flatworm Mesostoma, becoming detectable soon after the spindles achieve bipolarity. The furrows deepen during prometaphase, but ingression soon arrests.

MICROMORPHOGENESIS DURING DIATOM WALL FORMATION PRODUCES SILICEOUS NANOSTRUCTURES WITH DIFFERENT PROPERTIES(1).

Micromorphogenesis within the silica deposition vesicle (SDV) of the diatom Pinnularia viridis (Nitzsh) Ehrenb. resulted in distinct silica nanostructures and layers within forming valves and girdle bands. These siliceous components were similarly disclosed following alkaline etching of mature valves/girdle bands, where their different susceptibilities to dissolution over time resulted from apparent differences in silica density and/or chemistry.

Mitosis: spindle evolution and the matrix model.

Current spindle models explain "anaphase A" (movement of chromosomes to the poles) in terms of a motility system based solely on microtubules (MTs) and that functions in a manner unique to mitosis. We find both these propositions unlikely. An evolutionary perspective suggests that when the spindle evolved, it should have come to share not only components (e.

What generates flux of tubulin in kinetochore microtubules?

We discuss models for production of tubulin flux in kinetochore microtubules. Current models concentrate solely on microtubules and their associated motors and enzymes. For example, in some models the driving force for flux is enzymes at the poles and the kinetochores; in others the driving force is motor molecules that are associated with a stationary spindle matrix.