Discovery of novel gene regulating arbuscular mycorrhizal symbiosis

A majority of vascular plants, including most common crop species, are able to establish intracellular interactions with symbiotic arbuscular mycorrhizal (AM) fungi which provide plants the access to additional sources of inorganic phosphate in exchange for carbon compounds at highly branched fungal structures called arbuscules. The molecular mechanisms involved in subsequent control and maintenance of transcriptional activation during AM symbiosis is largely unknown. Comparative genome analysis identified a previously unidentified gene, which we have tentatively named FBK1, encoding an F-box/kelch-repeat (FBK) protein that is believed to be necessary for AM symbiosis due to its conserved nature in plants species that form the symbiosis. FBK proteins regulate cellular processes through ubiquitination and degradation of target proteins, such as transcription factors. We hypothesize that FBK1 regulates the development of AM symbiosis through the interaction and ubiquitination of transcription factors in the host cell nucleus. The gene is localized primarily in the nucleus of host cells. Plants with a mutated FBK1 genes had higher mycorrhizal colonization rate and less mature arbuscules. A yeast-two hybrid screen of a transcription factor library found that FBK1 interacts with only one transcription factor, RAM1, which is an essential regulator of arbuscule development. The protein FBK1 is therefore believed to be involved in the negative regulation of RAM1, degrading the RAM1 protein in the nucleus in order to decrease AM colonization. This control possibly allows for the host plant to adjust the symbiosis to prevent the exchange of fixed carbon with the AM fungi when phosphorus is not a limiting resource in the environment.

My Experience

During my time at BTI this summer, I have grown as a researcher, having gained a multitude of skills both in lab and for engaging with the world outside. Through planning and carrying out my research project with the support of my mentors, I not only learned hands-on skills imperative for experimentation, but also the interpersonal skills, independence and confidence essential for me in the future. The programming provided by BTI gave me a better understanding of the fellowship, networking and collaborative opportunities available to me as I look towards graduate school and my career beyond. These ten weeks surrounded by faculty, students, and fellow interns reinforced for me that plant science is a vibrant community, one in which I will continue to thrive.