Rapamycin induces morphological and physiological changes without increase in lipid content in Ustilago maydis

Area of Science:

• Mycology
• Cell Biology
• Biochemistry

Background:

• The conserved serine/threonine kinase TOR forms TORC1, regulating key cellular processes like ribosome biogenesis, autophagy, and lipid metabolism.
• TORC1 influences cell cycle progression, specifically extending the G2 phase.
• Rapamycin is a known inhibitor of TORC1.

Purpose of the Study:

• To investigate the impact of rapamycin on cell growth, morphology, and neutral lipid metabolism in the phytopathogenic fungus Ustilago maydis.
• To elucidate the role of TORC1 in U. maydis cellular physiology.

Main Methods:

• Treatment of U. maydis with rapamycin.
• Microscopic analysis of cell morphology and lipid body formation.
• Staining techniques (Blue-CMAC and BODIPY) for organelle differentiation.

Main Results:

• Rapamycin-induced TORC1 inhibition led to septa formation, separating post-mitotic nuclei.
• Accumulation of triacylglycerols was not observed, but large lipid bodies formed, suggesting fusion of smaller ones.
• Vacuoles exhibited behavior similar to lipid bodies, yet double labeling confirmed their independence.

Conclusions:

• TORC1 plays a significant role in regulating cell morphology in U. maydis.
• TORC1 influences neutral lipid metabolism and the dynamics of lipid bodies.
• TORC1 impacts vacuolar physiology and its relationship with lipid bodies in U. maydis.