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Updated: Dec 27, 2025
Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions
Published on: September 30, 2016
Rapamycin induces morphological and physiological changes without increase in lipid content in Ustilago maydis
Lucero Romero-Aguilar1, Guadalupe Guerra-Sánchez2, Eda P Tenorio1
1Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Cd. Universitaria, Coyoacán, 04510, Mexico City, Mexico.
Abstract:
The evolutionarily conserved serine/threonine kinase TOR recruits different subunits to assemble the Target of Rapamycin Complex 1 (TORC1), which is inhibited by rapamycin and regulates ribosome biogenesis, autophagy, and lipid metabolism by regulating the expression of lipogenic genes. In addition, TORC1 participates in the cell cycle, increasing the length of the G2 phase. In the present work, we investigated the effect of rapamycin on cell growth, cell morphology and neutral lipid metabolism in the phytopathogenic fungus Ustilago maydis. Inhibition of TORC1 by rapamycin induced the formation of septa that separate the nuclei that were formed after mitosis. Regarding neutral lipid metabolism, a higher accumulation of triacylglycerols was not detected, but the cells did contain large lipid bodies, which suggests that small lipid bodies became fused into big lipid droplets. Vacuoles showed a similar behavior as the lipid bodies, and double labeling with Blue-CMAC and BODIPY indicates that vacuoles and lipid bodies were independent organelles. The results suggest that TORC1 has a role in cell morphology, lipid metabolism, and vacuolar physiology in U. maydis.
Insights
Rapamycin treatment of Ustilago maydis inhibits Target of Rapamycin Complex 1 (TORC1), affecting cell division and causing lipid bodies to fuse. This study reveals TORC1
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.
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