Date of Award

12-31-2017

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology/Molecular, Cellular, and Organismal Biology

First Advisor

Richard V. Kesseli

Second Advisor

Linda Huang

Third Advisor

Kellee Siegfried

Abstract

Molecular techniques for guiding plant breeding have successfully used wild progenitors of domestic crops as sources of genetic variants conveying desirable traits. However, epigenetic variation, in particular DNA methylation, is a significant source of phenotypic variation and epigenetic effects of plant domestication are poorly understood. Described herein are the first single-base pair resolution methylomes of the highly valued crop iceberg lettuce (Lactuca sativa cv. Salinas) and its close relative, and ubiquitous weed, L. serriola. This work suggests several roles for acquisition and inheritance of methylation in the evolution of Lactuca spp. in response to stress. The Lactuca spp. have conserved patterns of methylation around genomic regions associated with biotic stress response and conserved changes in average methylation levels in genic and intergenic regions under nutrient deprived conditions. The genotypes also have important differences in both methylation levels and variability in both control and nutrient deprived conditions. Additionally, there are suggestions that abiotic stress associated methylation may be transmitted between generations with fidelity. Together these findings suggest an additional source and mechanism of genomic variation which may be isolated and adapted for improvement of crops.

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