Observation of the temporal dynamics of the cytoskeleton during cytokinesis in the brown alga <i>Sphacelaria rigidula</i> (Sphacelariales, Phaeophyceae)
<p>In cytokinesis of brown algae, the site at which microtubules (MTs) extending from centrosomes attached to daughter nuclei following nuclear division cross each other develops into a future division plane. An actin plate appears at this site, and a new cell partition membrane is formed. Cyt...
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2025
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| Summary: | <p>In cytokinesis of brown algae, the site at which microtubules (MTs) extending from centrosomes attached to daughter nuclei following nuclear division cross each other develops into a future division plane. An actin plate appears at this site, and a new cell partition membrane is formed. Cytokinesis progresses with outgrowth of the new cell partition membrane and not by ingrowth of furrows in the plasma membrane. The cytokinesis apparatus, composed of MTs and an actin plate, is thought to be involved in vesicle transport, accumulation and fusion to form a new cell partition membrane at the division plane; however, it remains unclear how they interact with each other to promote cytokinesis. To understand the relationship between the cytoskeleton and development of a new cell partition membrane, the behaviour of the cytoskeleton was observed during cytokinesis in living subapical cells of <i>Sphacelaria rigidula</i> by injecting fluorescently labelled phalloidin, actin or tubulin, and staining membranous structures with FM4-64FX. Double staining with Alexa Fluor 488-phalloidin and FM4-64FX revealed that the starting point of formation of a new cell partition membrane corresponded to the position where the actin plate would appear, and both expanded simultaneously, as observed in our previous studies. Cells injected with rhodamine-conjugated actin and HiLyte Fluor 488-conjugated tubulin showed a region of concentrated MTs extending from each centrosome, which appeared to be associated with the initiation of actin plate formation. The areas of the concentrated MTs changed with expansion of the actin plate. Double staining with HiLyte Fluor 488-conjugated tubulin and FM4-64FX revealed that MTs extended towards the edge of the new cell partition membrane. Although it was not possible to observe all three simultaneously, MTs were likely involved in the formation and expansion of the actin plate, and actin was involved in the new cell partition membrane formation.</p> <p>First observation of cytokinesis in living cells of brown algae.</p> <p>The actin plate is involved in membrane formation.</p> <p>Microtubules determine the position of actin plate formation.</p> |
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