NSF Postdoctoral Fellowship in Biology FY 2019: The Effects of Tomato Domestication on the Circadian Clock and its Interaction with Resistance to Phytophthora infestans

Mansfeld, Ben Nathan, East Lansing MI

Investigators

Abstract

This action funds an NSF National Plant Genome Initiative Postdoctoral Research Fellowship in Biology for FY 2019. The fellowship supports a research and training plan in a host laboratory for the Fellow who also presents a plan to broaden participation in biology. The title of the research and training plan for this fellowship to Ben Mansfeld is "The Effects of Tomato Domestication on the Circadian Clock and its Interaction with Resistance to Phytophthora infestans". The host institution for the fellowship is the Donald Danforth Plant Science Center and the sponsoring scientist is Dr. Rebecca Bart. Tomato is the second most important vegetable crop in the world, the fruit of which is eaten fresh or consumed in several processed products such as soups and sauces. Tomatoes are rich with important vitamins, minerals as well as antioxidants with potential anti-cancer and other healthful capabilities. The origin of the tomato plant is in equatorial countries in South America. As such, over millions of years, tomato plants have evolved a biological clock adapted to the day length around the equator. However, as humans domesticated tomatoes over the last few thousand years, they also traveled with the seeds, breeding tomatoes to be more successful crop plants in high latitude regions. Through this process, the tomato biological clock was altered to fit the new long days in these regions of the planet. The process of altering a crop's biological clock through domestication is not unique to tomato and may be quite common; however, because of its important role in regulating how the plant protects itself from disease and insects, an altered biological clock may thus increase a plant's susceptibility to disease. This research aims to use tomato as a model to better understand how crop domestication affected the biological clock and how this, in turn, may have affected the plant's innate ability to defend itself from disease. The overarching societal goal for this research is to contribute to increased crop defenses at a basic level, helping growers reduce their inputs and produce cheaper, sustainable food for a growing population. Training though this project will also further the Fellow's skills in plant genetics, genomics and plant-pathogen interactions. Broader impacts include mentoring high school and undergraduate students interested in learning more about bioinformatics, plant disease and crop improvement. This research will explore the hypothesis that alterations to the biological clock have affected cultivated tomato responses to infection, specifically by Phytophthora infestans, the pathogen that causes tomato and potato late blight. First, a collection of wild and domesticated tomato lines will be screened for their circadian rhythm traits, using an automatic camera system. A high-throughput bioassay will be then be used to screen if these lines show a different response to infection by P. infestans, at different times (a "gated" response). Transgenic tomato lines with altered clock rhythms will also be generated and screened to test the effects of mis-regulation of clock genes on the gated response to infection. The two lines showing strongest difference in gated response will be used in a 72-hour gene expression study, in which leaves will be inoculated with the pathogen at dawn and dusk and sampled every 4 hours for RNA sequencing. Weighted gene co-expression networks will then be used to compare the transcriptional responses of wild and domesticated tomato and identify hub genes at the center of network co-expression modules that differ between lines. Finally, to map loci contributing to differences in wild and domesticated tomato, a segregating population will be phenotyped and quantitative trait loci mapped using a bulk segregant approach. Candidate genes will be validated using CRISPR-based mutagenesis. All the data generated in this research will be made accessible through an online web application as well as through public repositories such as the NCBI's Short Read Archive (SRA), Dryad (https://datadryad.org), and the Sol Genomics Network (SGN; https://solgenomics.net). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.