Project: Comparative genomics of sea star responses to wasting disease
Taxon: Dermasterias imbricata, Leptasterias sp., Pisaster ochraceus, Pisaster brevispinus, Pycnopodia helianthoides
People: Dawson lab, University of California, Merced.
Place: Northeastern Pacific
Wildlife mass mortality events are increasing in frequency, driven in part by human perturbations, emerging viral diseases, intensifying toxic algal blooms, increasing temperatures, or a combination of multiple stressors. In the marine environment, disease emergence may be accelerated by environmental change, as warming and acidification can suppress the host immune response and favour the growth and spread of pathogens. Novel terrestrial microbes may be introduced to coastal waters where they encounter new hosts or change their pathogenicity. Marine infectious diseases, whether novel or endemic, have caused mass mortality events (MMEs) in diverse taxa, including plants, invertebrates and vertebrates of commercial and ecological importance. Understanding the genomic impacts of these events is crucial to understanding how to protect against and recover from them.
The 2013 outbreak of SSWD in the northeastern Pacific Ocean was remarkable for several reasons, including that both ecological and population genetic sampling were underway preceding the outbreak. Nonetheless, because the outbreak occurred so rapidly on a very large scale, causes and effects remain obscure. We have been conducting population genomic and comparative genomic analyses to provide a genomic understanding in retrospect — i.e. a genomic autopsy — of the impacts ad mechanisms of the disease.
To address some of the remaining knowledge gaps between observations of mortality and genomic responses, we are producing high-quality reference genomes, gene expression data from multiple life stages, tissue types, and disease statuses of sea stars, and undertaking epigenetic analyses too. Our goal is to discover genomic signals that tie together [1] ecological and experimental results available in the literature, [2] how gene expression differs between tissue types, ages (i.e., sizes), and disease status, [3] the extent to which expression responses to disease overlaps with expression responses to proposed causes, [4] whether expression differences are consistent with epigenetic modification, [5] to ask whether expression differences implicate specific immune pathways or are concordant with responses to wasting across species, and [6] to ascertain whether the implicated gene regions also showed allele frequency shifts in wasting-survivors, possibly indicating a link between mutations in coding/noncoding sequence and gene expression. Identification of genomic elements that respond in common across species or conditions should provide clues to the causes and conditions that increase the risk of wasting and may provide targets for genetic rescue.
References
DeBiasse, M.B., L.M. Schiebelhut, M. Escalona, E. Beraut, C. Fairbairn, M.P.A. Marimuthu,O. Nguyen, R. Sahasrabudhe, M.N Dawson. 2022. A chromosome-level reference genome for the giant pink sea star, Pisaster brevispinus, a species severely impacted by wasting. Journal of Heredity 113:689–698. https://doi.org/10.1093/jhered/esac044
Ruiz-Ramos, D.V., L.M. Schiebelhut, K.J. Hoff, J.P. Wares, & M.N Dawson. 2020. Initial comparative genomic autopsy of wasting disease in sea stars. Molecular Ecology 29:1087–1102. https://doi.org/10.1111/mec.15386
Schiebelhut, L.M., J.B. Puritz, & M.N Dawson. 2018. Decimation by sea star wasting disease and rapid genetic change in a keystone species, Pisaster ochraceus. Proceedings of the National Academy of Sciences of the USA 115:7069–7074. https://doi.org/10.1073/pnas.1800285115
Schiebelhut, L.M., M.B. DeBiasse, L. Gabriel, K.J. Hoff, & M.N Dawson. 2023. Chromosome-scale reference genome for the sunflower sea star, Pycnopodia helianthoides: a resource for ecological restoration. Journal of Heredity esad054 https://academic.oup.com/jhered/advance-article/doi/10.1093/jhered/esad054/7279103