A size-invariant bud-duration timer enables robustness in yeast cell size control.

Area of Science:

• Cell biology
• Molecular biology
• Genetics

Background:

• Cell size is critical for cellular function and proliferation across life.
• The G1/S phase boundary is a known checkpoint for cell size control.
• Regulation of cell size during the S/G2/M phases remains less understood.

Purpose of the Study:

• To investigate mechanisms controlling cell size after the G1/S checkpoint.
• To understand how cells regulate size during the S/G2/M phases of the cell cycle.

Main Methods:

• Utilized budding yeast with a reversible block at bud initiation.
• Allowed cells to grow significantly in volume while blocked.
• Observed cell cycle reentry and progeny size upon release from the block.

Main Results:

• Blocked cells grew over tenfold in volume compared to unperturbed cells.
• Released giant cells reentered the cell cycle, and their progeny returned to normal size.
• Observed behavior aligns with a size-invariant timer controlling S/G2/M duration.

Conclusions:

• Budding yeast utilize at least two distinct mechanisms for cell size homeostasis.
• A size-invariant timer likely regulates cell size during the S/G2/M phases.
• These mechanisms ensure proper cell size regulation throughout the cell cycle.