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(-) mating type-specific mutants of Phycomyces defective in sex pheromone biosynthesis

R P Sutter1, A B Grandin, B D Dye

  • 1Biology Department, West Virginia University, Morgantown 26506, USA.

Fungal Genetics and Biology : FG & B
|December 1, 1996
PubMed

Insights

Researchers identified mating type-specific mutants in Phycomyces blakesleeanus, revealing a gene essential for (-) mating type sex pheromone biosynthesis. This discovery revises our understanding of trisporic acid synthesis pathways.

Area of Science:

  • Mycology
  • Biochemistry
  • Genetics

Background:

  • Mucoraceous fungi, like Phycomyces blakesleeanus, exhibit mating types that regulate sexual reproduction.
  • Sex pheromone biosynthesis is crucial for initiating mating in these fungi, but its genetic regulation is not fully understood.
  • Previous models suggested a single enzyme catalyzed key steps in trisporic acid biosynthesis.

Purpose of the Study:

  • To isolate and characterize mating type-specific mutants in Phycomyces blakesleeanus.
  • To identify the gene involved in sex pheromone biosynthesis and its role in different mating types.
  • To revise the existing model of trisporic acid biosynthesis based on new experimental findings.

Main Methods:

  • Isolation of mating type-specific mutants in Phycomyces blakesleeanus.
  • Genetic analysis to identify the defective gene in both mating types.
  • Biochemical assays, including cross-feeding experiments, to detect pheromone precursors.
  • Characterization of precursor properties and comparison with known metabolites like 4-dihydrotrisporin.
  • Enzyme activity assays for pheromone biosynthesis and conversion to trisporic acid.

Main Results:

  • The first mating type-specific mutants in mucoraceous fungi were isolated, both defective in the same gene.
  • This gene is necessary only in the (-) mating type and codes for an enzyme in sex pheromone biosynthesis.
  • Mutants produced a pheromone precursor, identified as 4-dihydrotrisporin, detectable via cross-feeding.
  • Enzyme levels for pheromone biosynthesis are constitutively low, while conversion to trisporic acid is higher.
  • Mutants could convert (+) pheromone to trisporic acid, contradicting previous models.

Conclusions:

  • A revised model for trisporic acid biosynthesis is proposed, challenging existing literature.
  • The identified gene plays a critical, mating type-specific role in initiating pheromone production.
  • The distinct enzymatic activities in trisporic acid synthesis suggest a more complex regulatory mechanism than previously thought.

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