Biology subjects

Finnerty, J. R.

Publications and source records attributed to Finnerty, J. R..

4 recordsLinked to original sources

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

Holobiont transcriptomes for the critically endangered staghorn coral (Acropora cervicornis) from two environmentally distinct sites on Turneffe Atoll, Belize

Historically, staghorn coral (Acropora cervicornis) was a preeminent reef-builder in the Caribbean and Tropical Western Atlantic, where it constructed extensive thickets at 5-20 m depth that supported diverse ecosystems and provided coastal populations with food, storm protection, and income from tourism. In recent decades, A. cervicornis declined precipitously, up to 97% in some localities. To reverse its decline, widespread efforts are underway to characterize the phenotypic and genetic diversity of persisting populations with the goal of restoring them to historical levels by out-planting nursery grown specimens. To support this target, we developed transcriptomes for two A. cervicornis populations located in Turneffe Atoll Marine Reserve, Belize. These populations experience significantly different temperatures, light levels and water currents, and they harbor individuals that differ in key phenotypes. Because differentiating the gene activity of diverse taxa--i.e., coral host, algal photosymbiont, plus associated eukaryotes, bacteria, archaea, and viruses-- is critical to understanding the function of the coral holobiont, we developed a pipeline for parsing transcripts by taxon. Separate transcriptomes for each population contain complete representatives for >96% of 978 conserved metazoan single copy orthologs. The taxonomic breakdown of transcripts differed between sites, with more bacterial transcripts recovered from Calabash Caye and more symbiont transcripts from Blackbird Caye. The assembled transcriptomes will facilitate gene expression studies and in silico cloning from this endangered coral.

genomics↗

bioRxiv2021

An algal symbiont (Breviolum psygmophilum) responds more strongly to chronic high temperatures than its facultatively symbiotic coral host (Astrangia poculata)

Scleractinian corals form the foundation of coral reefs by secreting skeletons of calcium carbonate. Their intracellular algal symbionts (Symbiodiniaceae) translocate a large proportion of photosynthate to the coral host, which is required to maintain high rates of calcification. Global warming is causing dissociation of coral host and algal symbiont, visibly presented as coral bleaching. Despite decades of study, the precise mechanisms of coral bleaching remain unknown. Separating the thermal stress response of the coral from the algal symbiont is key to understanding bleaching in tropical corals. The facultatively symbiotic northern star coral, Astrangia poculata, naturally occurs as both symbiotic and aposymbiotic (lacking algal symbionts) polyps - sometimes on the same coral colony. Thus, it is possible to separate the heat stress response of the coral host alone from the coral in symbiosis with its symbiont Breviolum psygmophilum. Using replicate symbiotic and aposymbiotic ramets of A. poculata, we conducted a chronic heat stress experiment to increase our understanding of the cellular mechanisms resulting in coral bleaching. Sustained high temperature stress resulted in photosynthetic dysfunction in B. psygmophilum, including a decline in maximum photosynthesis rate, maximum photochemical efficiency, and the absorbance peak of chlorophyll a. Interestingly, the metabolic rates of symbiotic and aposymbiotic corals were differentially impacted. RNAseq analysis revealed more differentially expressed genes between heat-stressed and control aposymbiotic colonies than heat-stressed and control symbiotic colonies. Notably, aposymbiotic colonies increased the expression of inflammation-associated genes such as nitric oxide synthases. Unexpectedly, the largest transcriptional response was observed between heat-stressed and control B. psygmophilum, including genes involved in photosynthesis, response to oxidative stress, and meiosis. Thus, it appears that the algal symbiont suppresses the immune response of the host, potentially increasing the vulnerability of the host to pathogens. The A. poculata-B. psygmophilum symbiosis provides a tractable model system for investigating thermal stress and immune challenge in scleractinian corals.

ecology↗

bioRxiv2020

Phenotypic variation in two widespread Caribbean corals, Porites astreoides and P. divaricata, between mangrove and lagoon habitats

ABSTRACTAs coral reefs experience dramatic declines in coral cover throughout the tropics, there is an urgent need to understand the role that non-reef habitats such as mangroves play in the ecological niche of corals. Mangrove habitats present a challenge to reef-dwelling corals as they can differ dramatically from adjacent reef habitats with respect to key environmental parameters such as temperature and light. As variation in temperature and light within reef habitats is known to drive intraspecific differences in coral phenotype, we hypothesized that coral species which can exploit both reef and mangrove habitats will exhibit predictable differences in phenotype between habitats. To investigate how intraspecific variation, driven by either local adaptation or phenotypic plasticity, might enable particular coral species to exploit these two qualitatively different habitat types, we compared the phenotypes of two widespread Caribbean corals — Porites divaricata and P. astreoides— in mangrove versus lagoon habitats on Turneffe Atoll, Belize. We document significant differences in colony size, color, structural complexity, and corallite morphology between habitats. In every instance, the difference between mangrove and lagoon corals was consistent in P. divaricata and P. astreoides. This study is the first to document intraspecific phenotypic diversity in corals occupying mangrove versus patch-reef habitats, and it provides a foundation for understanding why some “reef coral” species can exploit mangroves, while others cannot.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗