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Differential expression of mepA, mepC and smtE during growth and development of Microbotryum violaceum
Carolyn F Hughes1, Michael H Perlin
1Department of Biology, University of Louisville, Louisville, Kentucky 40292, USA.
Abstract:
Many fungi require a dimorphic switch from budding to filamentous growth to cause infection. Although the control of dimorphism has been elucidated for organisms such as Saccharomyces cerevisiae and Ustilago maydis, almost nothing is known about the control of mating and dimorphism in Microbotryum violaceum. M. violaceum mepA, mepC and smtE are homologs of genes whose encoded products act as, or interact with, components of the MAPK and cAMP-PKA pathways, conserved pathways that regulate mating and dimorphism in other fungi. A comparison of gene expression under various in vitro conditions was superimposed on a comparison of in vitro vs. in planta expression to yield a more complete picture of the expression of these genes in M. violaceum during fungal development. For the most part the expression of these genes was highest on low ammonium, intermediate for mated and in planta, and lowest on rich medium. As expected, under conditions of low ammonium, expression of the M. violaceum ammonium permease genes mepA and mepC mirrors that of S. cerevisiae MEP2 and U. maydis ump2. An intriguing possibility is that MepA is a sensor to signal when conditions are conducive for mating. The upregulation of smtE, which encodes a PAK kinase, suggests that the MAPK pathway regulates, at least partially, mating and might be linked to ammonium sensing/transport in M. violaceum.
Insights
This study investigates fungal dimorphism in Microbotryum violaceum, revealing that ammonium levels influence key gene expression. MepA may act as a mating sensor, and the MAPK pathway is linked to mating and ammonium transport.
Area of Science:
- Mycology
- Molecular Biology
- Fungal Pathogenesis
Background:
- Fungal dimorphism, a switch from budding to filamentous growth, is crucial for infection.
- The genetic control of mating and dimorphism is well-studied in model fungi but poorly understood in Microbotryum violaceum.
Purpose of the Study:
- To investigate the regulation of mating and dimorphism in Microbotryum violaceum.
- To analyze the expression patterns of M. violaceum mepA, mepC, and smtE genes under different conditions.
Main Methods:
- Comparative gene expression analysis of M. violaceum under various in vitro conditions.
- Comparison of in vitro versus in planta gene expression.
- Identification of homologs to conserved fungal pathways (MAPK and cAMP-PKA).
Main Results:
- Gene expression of mepA, mepC, and smtE was highest under low ammonium conditions.
- Expression levels were intermediate for mated fungi and in planta, and lowest in rich medium.
- MepA and mepC expression mirrored S. cerevisiae MEP2 and U. maydis ump2 under low ammonium.
- Upregulation of smtE suggests MAPK pathway involvement in mating and ammonium sensing.
Conclusions:
- Ammonium availability significantly influences the expression of key genes involved in M. violaceum development.
- MepA may function as an environmental sensor signaling conditions favorable for mating.
- The MAPK pathway likely plays a role in regulating mating and is potentially linked to ammonium sensing and transport in M. violaceum.
