Author ORCID Identifier

https://orcid.org/0000-0001-7102-5959

Year of Publication

2019

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department

Biology

First Advisor

Dr. D. Nicholas McLetchie

Abstract

Plants are threatened by global change, increasing variability in weather patterns, and associated abiotic stress. Consequently, there is an urgent need to enhance our ability to predict plant community dynamics, shifts in species distributions, and physiological responses to environmental challenges. By building a fundamental understanding of plant stress tolerance, it may be possibly to protect the ecological services, economic industries, and communities that depend on plants. Dehydration tolerance (DhT) is an important mechanism of water stress tolerance with promising translational applications. Here, I take advantage natural variation in DhT to gain a deeper insight into this complex trait. In addition, I address questions related to the causes and consequences of sexual dimorphisms in DhT. Understanding sexual dimorphisms in stress tolerance is critical because these dimorphisms can drive spatial segregation of the sexes, biased sex ratios, and may ultimately reduce sexual reproduction and population persistence.

This work takes an integrated approach, addressing DhT on multiple scales from ecology, to physiology, to genomics in the tropical liverwort Marchantia inflexa. Initially, I tested for correlations between DhT and environmental dryness, sex differences in DhT, and genetic vs. plastic contributions to DhT variability. I found that patterns of variation in DhT are associated with environmental variability, including complex sexual dimorphisms, and derive from a combination of plasticity and genetic differences in DhT. Subsequently, I leveraged the variability in DhT to identify candidate DhT enhancing genes. In M. inflexa intraspecific differences in DhT are impacted by baseline variability among plants, as well as unique gene expression responses initiated during drying. In parallel, I assembled a draft genome assembly for M. inflexa, which was employed to investigate questions of sex chromosome evolution and sexual dimorphism in DhT. Finally, the bacteriome of M. inflexa was characterized and found to be extremely diverse and variable.

Collectively, this work adds to a growing understanding of DhT and highlights the importance of sampling approaches that seek to comprehensively describe variability in DhT. I detected complex patterns of variability in DhT among populations and the sexes of M. inflexa, which were used to gain insight into the genetic intricacies of DhT.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2019.190

Funding Information

This work was made possible through the generous support and funding provided by the University of Kentucky Department of Biology Ribble Endowment (research funding and a graduate fellowship), the American Bryological and Lichenological Society (Anderson and Crum Bryology Research Award and travel funding), the American Botanical Society (a fellowship and travel funding), the Kentucky Science and Engineering Foundation (grant no. KSEF-RDE-3048113194) (research and development grant that funded chapter 4), The Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants Program (grant no. RGPIN-2014-05820) (genome sequencing), and the Karri Casner Environmental Sciences Fellowship (research funding).

Available for download on Wednesday, November 13, 2019

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