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Two origins for the gene encoding alpha-isopropylmalate synthase in fungi

Erica M Larson1, Alexander Idnurm

  • 1Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri, United States of America.

Plos One
|July 27, 2010
PubMed
Abstract

Insights

Researchers identified the leuA gene in Phycomyces blakesleeanus, crucial for leucine biosynthesis. This finding supports the theory of multiple evolutionary origins for fungal metabolic pathways, possibly via horizontal gene transfer.

Area of Science:

  • Biochemistry
  • Mycology
  • Evolutionary Biology

Background:

  • Leucine biosynthesis is vital in prokaryotes, plants, and fungi, but absent in animals.
  • This pathway is a potential target for developing new antimicrobial therapies.

Purpose of the Study:

  • To identify the gene responsible for leucine biosynthesis in the fungus Phycomyces blakesleeanus.
  • To investigate the evolutionary origins of the leucine biosynthesis pathway in fungi.

Main Methods:

  • Genetic mapping using crosses between wild-type and leucine auxotrophic strains of Phycomyces blakesleeanus.
  • Functional complementation of a Schizosaccharomyces pombe leu3+ mutant using Phycomyces leuA.
  • Phylogenetic analysis of the leuA gene.

Main Results:

  • The leuA gene, encoding alpha-isopropylmalate synthase, was identified in Phycomyces blakesleeanus.
  • Phycomyces leuA successfully complemented the leucine auxotrophic phenotype in Schizosaccharomyces pombe.
  • Phylogenetic analysis indicates that the leuA gene in certain fungal groups (zygomycetes, chytrids) is more closely related to plant and bacterial homologs than to those in other fungi (ascomycetes, basidiomycetes).

Conclusions:

  • The identification of leuA in Phycomyces contributes to evidence suggesting that fungal metabolic pathways evolve through multiple events.
  • Horizontal gene transfer is proposed as a likely mechanism for the acquisition of these pathways in fungi.

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