I thought I'd point quickly to a really nice paper showing that the RNAi pathway, thought to be absent in budding yeasts, is actually only missing from baker's yeast, Saccharomyces cerevisiae. Remarkably, the authors are able to reconstitute the pathway (which was presumably present in the ancestor of all budding yeasts) in S. cerevisiae with exogenous expression of only two genes. The authors close with a remark about the role of contingency (in particular with regards to the choice of model organism) in research:

While anticipating a productive future for RNAi research in budding yeasts, we note that if in the past S. castellii [a yeast with an endogenous RNAi pathway] rather than S. cerevisiae had been chosen as the model budding yeast, the history of RNAi research would have been dramatically different.

Labels: Genetics