Biology subjects

Sharp, K. H.

Publications and source records attributed to Sharp, K. H..

3 recordsLinked to original sources

bioRxiv2024

Photosymbiont density is correlated with constitutive and induced immunity in the facultatively symbiotic coral, Astrangia poculata

Scleractinian corals, essential ecosystem engineers that form the base of coral reef ecosystems, have faced unprecedented mortality in recent decades due climate-change related stressors, including disease outbreaks. Despite this emergent threat to corals, many questions still remain regarding mechanisms underlying observed variation in disease susceptibility. Emergent data suggests at least some degree of variation in disease response may be linked to variability in the relationship between host corals and their algal photosymbionts (Family Symbiodineaceae). Still, the nuances of connections between symbiosis and immunity in cnidarians, including scleractinian corals, remain poorly understood. Here we leveraged an emergent model species, the facultatively symbiotic, temperate, scleractinian coral Astrangia poculata, to investigate associations between symbiont density and both constitutive and induced immunity. We used a combination of controlled immune challenges with heat-inactivated pathogens and transcriptomic analyses. Our results demonstrate that A. poculata mounts a robust initial response to pathogenic stimuli that is highly similar to responses documented in tropical corals. Furthermore, we document positive associations between symbiont density and both constitutive and induced immune responses, in agreement with recent preliminary studies in A. poculata. A suite of immune genes, including those coding for antioxidant peroxidoxin biosynthesis, are constitutively positively associated with symbiont density in A. poculata. Furthermore, variation in symbiont density is associated with distinct patterns of immune response; low symbiont density corals induce preventative immune mechanisms whereas high symbiont density corals mobilize energetic resources to fuel humoral immune responses. In summary, our study reveals the need for more nuanced study of symbiosis-immune interplay across diverse scleractinian corals, preferably including quantitative energy budget analysis for full disentanglement of these complex associations and their effects on pathogen susceptibility.

immunology↗

bioRxiv2023

Genomic comparison of the temperate coral Astrangia poculata with tropical corals yields insights into winter quiescence, innate immunity, and sexual reproduction

Facultatively symbiotic corals provide important experimental models to explore the establishment, maintenance, and breakdown of the mutualism between corals and members of the algal family Symbiodiniaceae. The temperate coral Astrangia poculata is one such model as it is not only facultatively symbiotic, but also occurs across a broad temperature and latitudinal gradient. Here, we report the de novo chromosome-scale assembly and annotation of the A. poculata genome. Though widespread segmental/tandem duplications of genomic regions were detected, we did not find strong evidence of a whole genome duplication (WGD) event. Comparison of the gene arrangement between A. poculata and the tropical coral Acropora millepora revealed 56.38% of the orthologous genes were conserved in syntenic blocks despite [~]415 million years of divergence. Gene families related to sperm hyperactivation and innate immunity, including lectins, were found to contain more genes in A. millepora relative to A. poculata. Sperm hyperactivation in A. millepora is expected given the extreme requirements of gamete competition during mass spawning events in tropical corals, while lectins are important in the establishment of coral-algal symbiosis. By contrast, gene families involved in sleep promotion, feeding suppression, and circadian sleep/wake cycle processes were expanded in A. poculata. These expanded gene families may play a role in A. poculatas ability to enter a dormancy-like state ("winter quiescence") to survive freezing temperatures at the northern edges of the species range.

genomics↗

bioRxiv2022

Variation in symbiont density is linked to changes in constitutive immunity in the facultatively symbiotic coral, Astrangia poculata

Scleractinian corals are essential ecosystem engineers, forming the basis of coral reef ecosystems. However, these organisms are in decline globally, in part due to rising disease prevalence. Most corals are dependent on symbiotic interactions with single-celled algae from the family Symbiodiniaceae to meet their nutritional needs, however suppression of host immunity may be essential to this relationship. To explore immunological consequences of algal symbioses in scleractinian corals, we investigated constitutive immune activity in the facultatively symbiotic coral, Astrangia poculata. We compared immune metrics (melanin synthesis, antioxidant production, and antibacterial activity) between coral colonies of varying symbiont density. Symbiont density was positively correlated to both antioxidant activity and melanin concentration. Our results suggest that the relationship between algal symbiosis and host immunity may be more complex than originally hypothesized and highlight the need for nuanced approaches when considering these relationships.

ecology↗