Understanding the effects of ploidal level on responses to global change in plants

Emily Sessa

Polyploidy, or whole genome duplication, occurs when an organism has one or more extra copies of all its chromosomes. This phenomenon is particularly common in plants, and recent estimates suggest that 15-30% of plants are polyploid. Polyploid species include a vast number of crop and other plants with economic and agricultural uses (e.g., cotton, wheat, potato, soybean). Polyploidy is known to influence a wide range of genetic and physiological features of plants, including physiological traits related to water use and photosynthesis. Polyploid plants can be more vigorous than diploids, have broader ecological niches, wider geographic distributions, and increased ability to invade new habitats, all driven by novel genetic combinations or gene expression patterns that can produce extensive changes in many traits. This project will investigate how polyploidy affects plants’ ability to respond to increases in temperature and decreases in available water (i.e., drought). Gene expression and physiological responses to drought and temperature will be measured for a set of fern species at different ploidal levels (amounts of polyploidy). Knowing whether and how ploidal level impacts these important components of the eastern forests of the United States will allow better prediction of how changes in temperature and water availability will influence community structure in natural ecosystems and will inform conservation efforts. Information on gene expression changes involved in tolerance of drought and increased temperatures has potential to assist crop breeding programs. An integral part of the project is to train postdoctoral associates, graduate students, and undergraduate students.

This project focuses on a set of fern species found in forests throughout the eastern United States. This is a naturally occurring plant system where polyploidy is prevalent, and whose members are ecologically important in the ecosystems where they occur. Gametophytes of six Dryopteris species, including two pairs of a polyploid and its parent taxa, will be grown in a multifactorial experiment with drought and temperature treatments. Data will be collected on reproductive and physiological ecology to determine how changes in temperature and water availability influence demographics and sporophyte recruitment from gametophytes as well as ability to recover from environmental stress. RNASeq will be used to generate gene expression profiles to evaluate differences between unstressed, dehydrated, and rehydrated gametophytes in different temperature treatments. Data will be analyzed using new methods for performing differential gene expression analyses on per-cell, per-biomass, and per-transcriptome bases. Results will be informative in quantifying the effects of experimental treatment on gene expression in organisms at different ploidy levels, including in crop plants and non-plant systems. The results of this work will improve the understanding of how ploidal level may influence species’ responses to environmental change. A workshop on how to effectively and engagingly teach plant life cycles will be held at the Botanical Society of America’s annual Botany conference, and will use a data-driven approach that incorporates results from the research.