Gene loss, repression, amplification, and horizontal acquisition shape galactose/melibiose metabolism in fission yeast.
Natural variation in metabolism is a key driver of microbial adaptation. While galactose utilization is well studied in budding yeasts, it remains poorly understood in the fission yeast  Schizosaccharomyces pombe . Here, we reveal extensive natural variation in galactose utilization across  S. pombe  isolates-from complete deficiency (Gal - ) to exceptionally fast growth (Gal F ). Gal -  strains fall into two classes: one with deletions of the  gal  gene cluster (via three distinct mechanisms) and another with intact but repressed  gal  genes. In contrast, Gal F  is driven by an amplified gene cluster absent from the reference genome-the  gal - mel  cluster (GMC)-which also confers melibiose utilization (Mel + ). Mel +  is exclusively linked to the GMC, except in one strain harboring a standalone melibiase gene. Phylogenetic analyses indicate that horizontal gene transfer may underlie these adaptive traits. Together, our work demonstrates how diverse mechanisms-gene loss, repression, amplification, and horizontal acquisition-shape metabolic diversity and ecological specialization in fission yeast.
Du XM, Suo F, Du LL