Variable pathways for developmental changes in composition and organization of microtubules in Physarum polycephalum

Area of Science:

• Cell Biology
• Developmental Biology
• Cytoskeletal Dynamics

Background:

• The amoebal-plasmodial transition (APT) in myxomycetes involves significant cellular reorganization.
• This transition includes loss of flagellar axonemes, altered mitosis, and changes in cytoskeletal microtubules.
• These structural changes are accompanied by shifts in expressed tubulin proteins.

Purpose of the Study:

• To investigate the timing of tubulin isotype loss and accumulation during the APT in Physarum polycephalum.
• To determine if changes in microtubule composition correlate with changes in microtubule organization.
• To understand the relationship between tubulin dynamics and cellular events during development.

Main Methods:

• Immunofluorescence microscopy was used to track tubulin isotypes.
• Developmentally regulated tubulin isotypes (beta 2-tubulin and alpha 3-tubulin) were studied.
• Microtubule organization and microtubule-organizing centers (MTOCs) were analyzed in relation to tubulin changes.

Main Results:

• Plasmodium-specific beta 2-tubulin appeared in committed uninucleate cells, with variations in timing.
• Amoeba-specific acetylated alpha 3-tubulin gradually disappeared, with timing differences across cell stages.
• Cytoplasmic microtubules persisted until late stages, and MTOC number varied, showing no strict correlation with tubulin composition changes.

Conclusions:

• Changes in tubulin composition, specifically beta 2-tubulin accumulation and alpha 3-tubulin disappearance, are not sufficient to drive microtubule reorganization during APT.
• Individual cells exhibit distinct temporal patterns for tubulin isotype dynamics and other cellular changes during development.
• The APT involves complex, cell-specific coordination of cytoskeletal and molecular events.