VIDA Seagrass: Viral Infection Dynamics Among Seagrasses

Microbiomes, which include all microbes (archaea, bacteria, fungi, protists, and viruses) associated with a given organism, influence a plant’s condition and productivity via processes such as nutrient uptake, immunity or evolution of the host. Although disease is often the first word that comes to mind when thinking about viral interactions, some viruses can coexist with their host without causing negative effects. In fact, many viruses have evolved to reside within their hosts for long periods of time with minimal or even beneficial effects. For example, studies have documented reproductive benefits, heat and drought tolerance, cross-protection against other microorganisms and insect deterrence from persistent viral infections. Much of the available information on plant viruses is obtained from diseased cultivated plants rather than symptomless wild plants. Moreover, the effects of viral infections are well documented and understood for terrestrial plants, but research efforts are generally lacking for marine plants like seagrasses. To date, only 13 viruses, five of which were reported within the last three years, were documented within five of the 60+ seagrass species. One of these species, Thalassia testudinum or turtlegrass, is the dominant species within Florida, not to mention the Gulf of Mexico and Caribbean. Unfortunately, little is known about viral infections in seagrasses. To address this knowledge gap, researchers from the University of South Florida (USF), University of North Florida (UNF) and FWRI formulated a collaborative research project: VIDA Seagrass – Viral Infection Dynamics Among Seagrasses.

A novel seagrass virus, turtlegrass virus X (TVX), was first identified in 2016 within Tampa Bay, Florida by researchers from the University of South Florida and FWRI. But what is TVX? What factors are responsible for the distribution of TVX within a seagrass meadow? What are the effects of TVX on turtlegrass? VIDA will attempt to provide base knowledge about seagrass-virus interactions using a two-tiered approach involving field and laboratory studies of turtlegrass and TVX. Field surveys (Tier I) will determine whether seagrass-virus interactions are positive, neutral or negative, and if seagrass genotypic diversity influences virus distribution within a natural population where TVX has persisted for at least five years. To explore the drivers of viral infection, we will monitor individual shoots in a seagrass bed within Tampa Bay, Florida composed of both TVX-positive and negative plants. We will measure turtlegrass abundance (shoot density), phenology (presence or absence of flowers/fruits), morphology and growth (leaves per shoot, canopy height, leaf width/length, leaf growth), condition (presence or absence of dead tissue) and mortality as it relates to viral load and genotype. In the lab, we will set up microcosm experiments (Tier II) to evaluate turtlegrass responses to TVX infection at the physiological (survival, photochemical capacity, cellular responses) and molecular (transcriptomic) levels, and assess how these responses are affected under salinity stress. 

It is important to gain a more comprehensive understanding of how environmental changes may alter seagrass-virus dynamics as salinity stress has been linked to turtlegrass mortality in Florida. Results will shed light on implications for seagrass production and resilience in the face of climate change and human-induced stressors. Currently, there are no experimental marine plant-virus pathosystems; therefore, establishing the first seagrass-virus study system will overcome a major barrier limiting research into viral infection dynamics in seagrasses and will serve as a model for investigating the growing number of seagrass viruses discovered through sequencing efforts.