The Molecular and Evolutionary Outcomes of Transgenerational Plasticity in Mimulus guttatus

Abstract

Derived from the same family line, in the same greenhouse, and self-pollinated in an identical fashion, what effect could hole-puncher induced leaf damage have on the offspring of these individuals? Across three independent experiments during my graduate career I have demonstrated the diverse array of lingering epigenetic, gene expression, phenotypic, and fitness effects that simple mechanical wounding has on the following generation. While focused initially on the epigenetic and gene expression basis of increased trichome density in the offspring of damaged plants, it became clear early on that a host of other pathways were also differentially regulated. In the end I identified hundreds of differentially expressed genes and thousands of genomic regions where DNA methylation varied depending on parental wounding. Along with identifying numerous differentially regulated hormone synthesis genes and secondary metabolism pathways, I twice confirmed the differential regulation of the previously identified transgenerationally plastic Mimulus guttatus MYB Mixta-like 8 (MgMYBML8). A brief foray into molecular epigenetics and gene expression modeling provided our lab with the necessary information to utilize DNA methylation data and test hypotheses regarding the role of DNA methylation on transgenerational inheritance. Finally, through the use of a two-generation common garden experiment I demonstrated that transgenerational effects alter the development and resistance of plants in nature. While much remains to be deciphered regarding the molecular underpinnings, evolutionary role, and ecological relevance of transgenerational inheritance, the work presented herein provides a relatively comprehensive look at the complexity underlying an extremely simplified case of transgenerational inheritance.