  The Leloir galactose utilization or GAL pathway of budding yeasts, including
that of the baker's yeast Saccharomyces cerevisiae and the opportunistic human
pathogen Candida albicans, breaks down the sugar galactose for energy and
biomass production. The GAL pathway has long served as a model system for
understanding how eukaryotic metabolic pathways, including their modes of
regulation, evolve. More recently, the physical linkage of the structural genes
GAL1, GAL7, and GAL10 in diverse budding yeast genomes has been used as a model
for understanding the evolution of gene clustering. In this opinion, we
summarize exciting recent work on three different aspects of this iconic
pathway's evolution: gene cluster organization, GAL gene regulation, and the
population genetics of the GAL pathway.
