Coding fungal tandem repeats as generators of fungal diversity

Coding tandem repeats are adjacent sequences that are directly repeated. The repeated units can be identical or partially degenerate. They are completely contained within a coding sequence and are composed of repeated units in which copy number does not disrupt the reading frame. They have been observed in viruses, prokaryotes and eukaryotes. The benefits offered by repeats include the modular construction of new proteins and introduction of rapidly evolving protein sequences which allow faster adaptation to new environments. Here we review the subject of tandem repeats and their relevance in fungi. Emphasis is given to repeat-containing fungal cell wall proteins and their role in generating diversity, adaptation to the environment, immunogenicity, adhesion, and pathogenesis. We describe in detail the recent studies analyzing coding tandem repeats in the model yeast Saccharomyces cerevisiae and the important human pathogens Candida albicans and Aspergillus fumigatus. Numerous unanswered questions are highlighted, providing a rich hunting ground for future research.