A mutation in Aspergillus nidulans that blocks the transition from interphase to prophase

Area of Science:

• Molecular Biology
• Cell Biology
• Mycology

Background:

• Mitotic synchrony is crucial for studying cell division.
• Heat-sensitive mutations offer tools to control cell cycle progression.
• Aspergillus nidulans is a model organism for eukaryotic cell biology.

Purpose of the Study:

• To develop a method for achieving mitotic synchrony in Aspergillus nidulans.
• To characterize the function of heat-sensitive nim mutations in the nuclear division cycle.
• To investigate the role of nimA5 in controlling microtubule assembly and chromosomal condensation.

Main Methods:

• Characterization of heat-sensitive nim mutations.
• Temperature shift experiments using the nimA5 mutant strain.
• Electron microscopy to examine mitotic spindle formation.

Main Results:

• The nimA5 mutation blocks the nuclear division cycle at interphase at restrictive temperatures.
• Shifting nimA5 to permissive temperatures rapidly induces mitosis (78% mitotic index in 7.5 min).
• Mitotic spindles are absent at restrictive temperatures and form gradually upon release.

Conclusions:

• The nimA5 mutation provides a tool for studying microtubule assembly and chromosomal condensation.
• nimA5 controls the initiation of these processes, allowing for cell cycle synchronization.
• Spindle formation, while rapid, is a gradual process involving increasing microtubule numbers.