Timing and function of chitin synthesis in yeast.

Area of Science:

• Cell Biology
• Biochemistry
• Mycology

Background:

• Yeast cell cycle progression involves bud formation and septum development.
• Chitin is a primary component of the septum in Saccharomyces cerevisiae.

Purpose of the Study:

• To investigate the precise timing of chitin synthesis during the yeast cell cycle.
• To understand the role of chitin in septum formation and cell viability.

Main Methods:

• Utilized a temperature-sensitive yeast mutant (L-2-42) to arrest cells at a specific cell cycle stage.
• Employed tritiated glucose to trace chitin synthesis.
• Used Polyoxin D, a chitin synthesis inhibitor, and a fluorescent brightener to assess chitin presence and localization.

Main Results:

• Chitin synthesis is initiated early in the cell cycle, preceding septum closure.
• Early chitin synthesis is not essential for bud emergence or growth.
• Inhibition of chitin synthesis leads to cell lysis due to failed septum formation.
• Fluorescence localization confirms chitin deposition at the bud-mother cell junction shortly after bud emergence.

Conclusions:

• Chitin synthesis begins at or shortly after bud emergence in Saccharomyces cerevisiae.
• Proper septum formation, dependent on chitin, is crucial for yeast cell viability.
• A model for chitin synthesis and primary septum formation is proposed based on these findings.