Oregon State University
Systems Science in Marine Biology
In the SSiMBio group, I am involved in developing an Anthopleura elegantissima reference transcriptome and profiled gene expression, testing for changes in gene expression across latitudes at different tidal heights and in different symbiotic states. When examining effects of symbiont type, we found striking gene expression patterns, with genes only up-regulated in one symbiont type, while down-regulated in the other two types. This pattern is reproducible on a large number of genes and is affected by the presence and type of symbiont, evident in the almost perfect clustering. We found no significant effects of tidal height, but did find that site had a large effect even though it did not correlate with latitude. This difference may be explained by site-specific complexity, and that the signal we see may be due to site-specific factors. This study was an exciting first glimpse at the biological responses of A. elegantissima and we’re excited to integrate this dataset across multiple levels.
In the SSiMBio group, I am building genomic resources for the temperate sea anemone Anthopleura elegantissima which will provide a model for symbiosis and environmental stress tolerance. A. elegantissima presents variation in visually distinct symbiotic states, associating with a green alga (Elliptochloris marina), a dinoflagellate (Symbiodinium muscatinei), and occurs in an aposymbiotic state (without algal symbionts). Maintenance of associations in the thermally dynamic intertidal zone and across a wide latitudinal range is extremely interesting especially in contrast to the more thermally sensitive associations in corals. To establish genomic resources for this model, I collected anemones across their geographic range and conducted genome-wide SNP genotyping to select a relatively homozygous colony to sequence. I constructed a draft genome assembly for A. elegantissima from the chosen accession. I have also made a genetic linkage map for A. elegantissima. We will continue to document our ongoing efforts to annotate the genome and integrate the genome, transcriptome, and linkage map in order to provide the genomic resources necessary to aid in our research of this emerging model system.
In the SSiMBio group, I am involved in three projects: measuring carbon and nitrogen stable isotope differences in Anthopleura elegantissima and it's two algal symbionts (Elliptochloris marina and Symbiodinium muscatinei) to determine how the importance of heterotrophy and photoautotrophy changes with symbiont type, latitude, and tidal position; measuring carbonic anhydrase activity levels in A. elegantissima to determine how the need for inorganic carbon is changing with different symbiont types, at different latitiudes, and tidal positions; and using quantitative PCR to determine how the ratio of symbionts relative to host changes across latitude and at different tidal positions. When examining effects of symbiont type on stable isotope composition, we found that regardless of symbiont type, the sea anemones are primarily relying on heterotrophic feeding to provide nutrition for growth and maintenance. These findings partially explain why A. elegantissima occurs in an aposymbiotic state and suggests that both the algal symbionts may be more like parasites than mutualists in this symbiotic relationship. When we examined the symbionts themselves, we found that S. muscatinei has a lighter carbon and nitrogen composition compared to E. marina. This finding is not surprising as it is well known that S. muscatinei is more productive than E. marina and is therefore less 'picky' about it's carbon and nitrogen species because it is going through photosynthesis much quicker than E. marina.
My work in the SSiMBio group relates to the analysis of the microbial communities associated with Anthopleura elegantissima. I have conducted 16S amplicon sequencing to take a census of the microbes living on and in the tissues of the anemone. Early analyses suggest that the symbiotic state—whether the anemone is hosting Elliptochloris, Symbiodinium, or no algae—appears to have a strong effect on the structure of the microbial communities associated with the anemones. The effect of symbiotic state is more apparent than any other variables examined, including latitude (samples were collected from California to Washington) and tidal position.
Anthopleura elegantissima can be found in aposymbiotic and symbiotic states, as well as form symbioses with two different symbionts. Since the holobiont environment is altered by the presence of symbionts, we expect there to be differential expression of a subset of genes and subsequent changes in protein levels. Previous studies in the Weis lab found that one of the most highly upregulated genes in symbiotic A. elegantissima was sym32, which belongs to the fasciclin I family involved in cell adhesion and signaling. In the SSiMBio group, I am involved in measuring Sym32 protein levels across our collection of A. elegantissima samples using enzyme-linked immunosorbent assays (ELISAs). We are interested in finding potential differences between A. elegantissima with different symbionts, as well as seeing if these levels correlate with host:symbiont biomass ratios.