Project description:Heat-evolved Symbiodiniaceae can improve the physiological performances of their coral host under heat stress, but their gene expression responses to heat remained unknown. We explore here the transcriptomic basis of differential thermal stress responses between in hospite wild-type and heat-evolved Cladocopium proliferum strains and their coral host Platygyra daedealea.
Project description:Reef-building corals live in a mutualistic relationship with photosynthetic algae (family Symbiodiniaceae) that usually provide the bulk of the energy required by the coral host. This relationship is very sensitive to temperature stress, with as little as 1°C increase above mean in sea surface temperatures (SSTs) often leading to the collapse of the association. The meta-stability of these associations has led to interest in the potential of more stress tolerant algae to supplement or substitute for the normal Symbiodiniaceae mutualists. In this respect, the apicomplexan-like microalga Chromera is of particular interest as it is considerably more temperature tolerant than are most members of the Symbiodiniaceae. Here we generated a de novo transcriptome for a Chromera strain isolated from a GBR coral (“GBR Chromera”) and compared to those of the reference strain of Chromera (“Sydney Chromera”), and to those of Symbiodiniaceae algae (Fugacium, Cladocopium and Breviolum), as well as the apicomplexan parasite, Plasmodium falciparum. By contrast with the Symbiodiniaceae, the two Chromera strains had a high level of sequence similarity evident by very low levels of divergence in orthologous genes. Although surveys of specific KEGG categories provided few general criteria by which true coral mutualists might be identified, they provide a molecular rationalization for the near ubiquitous association of Cladocopium strains with Indo-Pacific reef corals in general and with Acropora spp. in particular. In addition, HSP20 genes may underlie the higher thermal tolerance shown by Chromera compared to Symbiodiniaceae
Project description:Coral disease is one of the major causes of reef degradation and therefore of concern to management and conservation efforts. Dark Spot Syndrome (DSS) was described in the early 1990’s as brown or purple amorphous areas of tissue on a coral and has since become one of the most prevalent diseases reported on Caribbean reefs. It has been identified in a number of coral species, but there is debate as to whether it is in fact the same disease in different corals. Further, it is questioned whether these macroscopic signs are in fact diagnostic of an infectious disease, since they can also be caused by physical injury in some species. The most commonly affected species in the Caribbean is the massive starlet coral Siderastrea siderea. We sampled this species in two geographic locations, Dry Tortugas National Park and Virgin Islands National Park. Tissue biopsies were collected from both healthy colonies with normal pigmentation and those with dark spot lesions. Microbial-community DNA was extracted from coral samples (mucus, tissue, and skeleton), amplified using bacterial-specific primers, and applied to PhyloChip™ G3 microarrays to examine the bacterial diversity associated with this coral. Samples were also screened for the presence of a fungal ribotype that has recently been implicated as a causative agent of DSS in another coral species, however the amplicon pools were overwhelmed by coral 18S rRNA genes from S. siderea. Unlike a similar study on a white-plague-like disease, S. siderea samples did not cluster consistently based on health state (i.e., normal versus dark spot). Various bacteria, including Cyanobacteria and Vibrios, were observed to have increased relative abundance in the discolored tissue, but the patterns were not consistent across all DSS samples. Overall, our findings do not support the hypothesis that DSS in S. siderea is linked to a bacterial pathogen or pathogens. This dataset provides the most comprehensive overview to date of the bacterial community associated with the healthy scleractinian coral S. siderea. 17 samples, coral tissue punches from healthy and also from dark-spot-affected Siderastrea Siderea coral in the Virgin Islands and the Dry Tortugas National Parks was collected for comparison of associated bacterial communities