Rapid expansion and functional divergence of subtelomeric gene families in yeast

Subtelomeres, regions proximal to telomeres, exhibit characteristics unique to eukaryotic genomes. Genes residing in these loci are subject to epigenetic regulation and elevated rates of both meiotic and mitotic recombination. However, most whole genome sequences do not contain assembled subtelomeric sequences and, as a consequence, these regions are often overlooked in comparative genomics. For these reasons, our understanding of the evolution of subtelomeric regions is based on generalizations drawn from anecdotal accounts of individual gene families. In this manuscript, we comprehensively study the evolution and functional divergence of subtelomeric gene families in the yeast lineage. In Chapter 1, the current knowledge about subtelomeres and their gene structure in various organisms is summarized. In Chapter 2, we show computationally that subtelomeric families are evolving and expanding much faster than families that do not contain subtelomeric genes in the yeast lineage. In Chapter 3, we show experimentally how duplication and functional divergence of three related subtelomeric MAL gene families yields novel alleles that allow metabolism of different carbohydrates. In Chapter 4, we summarize our main findings and speculate that the increased instability of eukaryotic subtelomeres supports rapid adaptation to novel niches. We conclude by noting future directions of investigation regarding the evolution of eukaryotic subtelomeres.