With climate change models predicting increased variation in global weather patterns, including frequent and intense droughts, both ecological stability and food security are threatened. In order to protect the communities and industries that rely on agricultural productivity, it is critical that we work towards strategies to enhance water-stress tolerance in crops. These efforts should include building a fundamental understanding of the many natural adaptations to water scarcity, which span diverse life histories, morphologies, and physiologies. This diversity represents a valuable repository of information that can be mined to gain insight into the biology of water-stress tolerance. My research is focused on understanding the mechanisms of desiccation tolerance, which enables tissues to recover from extreme drying (below an absolute water content of -100M Pa). When desiccated, tissues enter a state of quiescence where (nearly) all metabolic activity ceases, and this allows them to persist through long and intense periods of drought. The advantages of this trait, if applied to crops in drought prone and marginal sites, cannot be overstated.
Mechanisms of desiccation tolerance in the South African resurrection plant Myrothamnus flabellifolia
Filling knowledge gaps in our understanding of desiccation tolerance is an important step towards preventing drought induced losses and ensuring global food security. Currently I am working to establish a diversity panel of the unique and understudied resurrection plant Myrothamnus flabellifolia, which will be leveraged to pinpoint genetic and physiological variation giving rise to elevated desiccation tolerance. The study is integrated across organizational scales, addressing ecological, physiological, and genomic components of desiccation tolerance. Currently, we are working to establish field sites across southern Africa to monitor long-term ecological dynamics of M. flabellifolia. These data will be paired with the genomic resources we are developing, allowing us to investigate the impact of natural diversity and genetic variation on adaptive phenotypes.
In addition to being desiccation tolerant, M. flabellifolia produces a robust profile of secondary compounds with important medicinal applications, and our work includes a plan to engage local communities in the sustainable cultivation of M. flabellifolia for medicinal purposes.
This project is in its infancy and there is a lot of room to explore, so please feel free to reach out if you have ideas or want to get involved.
BRYOPHYTE ECOLOGY and EVOLUTION
Genomics and sex chromosome evolution of Marchantia inflexa
Bryophytes (mosses, liverworts, and hornworts) are living representatives of an early diverging land plant lineage, and they provide an important landmark for comparative phylogenetics. Building a fundamental understanding of genomic patterns can be readily accomplished by working with bryophytes because of their small genomes, many of which contain comparatively few paralogous duplications of regulatory genes. Interestingly, bryophytes harbor a high proportion of dioecious species. Nearly half of all extant mosses, and approximately two-thirds of liverworts are dioecious, and this provides an ideal system in which to untangle the complex biology of sex in plants. Additionally, the haploid gametophyte is the dominant life stage in bryophytes, and this offers a unique perspective on the evolution of sex-linked genes, as the female (U) and male (V) sex chromosomes are present at the same copy number (1N) as autosomal chromosomes for the majority of the organism’s life cycle and are subject to haploid selection. We took advantage of these characteristics to gain insight into how haploid selection shapes sex chromosome evolution and to identify genomic signatures of stress tolerance, both of which inform our understanding of early plant evolution.
Eco-physiology of desiccation tolerance in Marchantia inflexa
My PhD work focused on characterizing the ecophysiology of desiccation tolerance in the tropical liverwort Marchantia inflexa. We took advantage natural variation in desiccation tolerance among populations to gain deeper insight into the causes and consequences of sexual dimorphisms in desiccation tolerance. Understanding sexual dimorphisms in stress tolerance is important because these dimorphisms can drive spatial segregation of the sexes, lead to biased population sex ratios, and may ultimately reduce sexual reproduction and population persistence. In general, we found that that plants were increasingly desiccation tolerant in drier sites, due to a combination of local adaptation and plasticity. Complex sexual dimorphisms were also detected, which likely contribute to population level dynamics.
Plant-microbe interactions have major implications for agricultural productivity, ecosystem function, and nutrient cycling. However, information on the establishment, diversity, and function of the plant microbiome remains limited, especially for non-vascular plants. In an effort to fill this knowledge gap, we described the bacteriome of the tropical liverwort Marchantia inflexa. We found that the bacteriome is abundant, diverse, and shows similarities with other non-vascular plant lineages. On the basis of known microbial functions, our analyses suggest that the specific taxonomic assemblages of bacteria detected in different sites may serve functional roles; allowing plants to better acclimate to their local environment. Our data also suggest that sex differences in the bacteriome may correspond to subtle differences in the morphology of the sexes.
Currently, we (mostly Caylyn Railey, a brilliant undergraduate working on the project) are testing if a functional link exists between the plant bacteriome composition and desiccation tolerance. Caylyn is growing multiple lines of M. inflexa under aseptic culture and characterizing subsequent changes desiccation tolerance.