MCA: Diversity of mycoviruses in fungal endophytes and their cryptic roles in plant health

Bowie State University, Bowie MD

Investigators

Abstract

Microbes are ubiquitous and associated with almost all living organisms. The associations or interactions microbes have with their hosts may range from beneficial to detrimental, and may be direct or indirect. However, considering that there are trillions of microorganisms on Earth, much of that diversity and their interactions are unknown. A poorly studied group are viruses. The objective of this project is to begin to discover the diversity of viruses that inhabit fungi (a.k.a. mycoviruses) that live inside plants, the effects of mycoviruses on those fungi, and the indirect interactions and consequences on the plant hosts. One hypothesis of this study is that mycoviruses serve as an “invisibility cloak”, so that fungus can penetrate the plant without activating the plant defenses. The project will focus on beneficial and pathogenic fungi that inhabit coffee plants. While some mycoviruses may make a fungus more pathogenic on its plant host, others may make them less pathogenic (=hypovirulent mycoviruses), thus having potential applications in the engineering of those fungi to benefit crops. For example, inoculating hypovirulent mycoviruses into a plant pathogenic fungus to make it non-pathogenic, or, on the other hand, inoculating a beneficial fungus so that it can colonize an whole plant and provide a broad and innate protection against diseases or the effects of climate (e.g., drought or high temperatures). The project will also contribute to the growth of Bowie State University’s research agenda and the training of students at the first historically black college/university (HBCU) in Maryland. The project will study the diversity of mycoviruses (viruses of fungi) and their effects on endophytic fungi, the plant hosts, and consequently, the tripartite symbiosis (virus-fungus-plant). The specific objectives of the project are to assess the diversity of mycoviruses in a selected collection of fungal endophytes from wild Rubiaceae (the coffee family); determine if there is a phylogenetic and mycovirus-incidence relationship between the plant, host fungus, and the mycovirus; and compare, in vitro and in planta, the effects of mycovirus-infected and mycovirus-free endophytic fungi. The objectives will be accomplished by collecting and identifying the fungi associated to wild Rubiaceae plants in Costa Rica, screening them for mycoviruses using traditional and metagenomic/metatranscriptomic approaches, eradicating the mycoviruses from the fungi, and assessing the effects of mycovirus eradication on the phenotype of the fungus (i.e., fungal growth rate in vitro, antagonistic ability in vitro, and in planta capacity to infect and become endophytic). Results from this project will add mycoviruses as another potential group to control plant pathogenic fungi. For example, if mycoviruses are not host-specific, it may be possible to infect plant pathogens or mutualists with hypovirulent mycoviruses. In addition to mycoviruses, from the metagenomic and metranscriptomic data, we may obtain data from endohyphal bacteria and phages, which are attractive in the discovery of new CRISPR-Cas systems. 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.