Saliva is the first stop for food, microorganisms, and other xenobiotic molecules entering our bodies. It regulates microbial composition, helps with predigestion, taste perception, and overall hemostasis of the oral cavity. This direct environmental interaction makes saliva an ideal candidate for evolutionary pressures. An amazing example of this is the amylase gene (AMY), which codes for a starch-digesting enzyme in animals. Previous studies have found that AMY underwent several gene copy number gains in humans, dogs and mice, possibly along with increased starch consumption during the evolution of these species.
In this study, we present comprehensive evidence for AMY copy number expansions that independently occurred in several mammalian species which consume diets rich in starch. We also provided correlative evidence that AMY gene duplications may be an essential first step for amylase to be expressed in saliva. Our findings underscore the overall importance of gene copy number amplification as a flexible and fast evolutionary mechanism that can independently occur in different branches of the phylogeny. In this study, I led the collaborative effort to collect mammalian DNA and saliva samples from across the globe, including wolves, African pouched rats, wild boars, and non-human primates, to name a few.
Additionally, during this effort I was able to deduce that the likely mechanism for independent AMY duplication was through retrotransposon events. Overall, the experience in this project connected my training in bioinformatics to the wet-lab bench involving enzymatic activity in saliva, providing me with project I was able to take full circle.