Development and application of molecular biomarkers for characterizing Caribbean Yellow Band Disease inOrbicella faveolata

Abstract

Molecular stress responses associated with coral diseases represent an under-studied area of cnidarian transcriptome investigations. Caribbean Yellow Band Disease (CYBD) is considered a disease of Symbiodinium within the tissues of the coral host Orbicella faveolata. There is a paucity of diagnostic tools to assist in the early detection and characterization of coral diseases. The validity of a diagnostic test is determined by its ability to distinguish host organisms that have the disease from those that do not. The ability to detect and identify disease-affected tissue before visible signs of the disease are evident would then be a useful diagnostic tool for monitoring and managing disease outbreaks. Representational Difference Analysis (RDA) was utilized to isolate differentially expressed genes in O. faveolata exhibiting CYBD. Preliminary screening of RDA products identified a small number of genes of interest (GOI) which included an early growth response factor and ubiquitin ligase from the coral host as well as cytochrome oxidase from the algal symbiont. To further characterize the specificity of response, quantitative real-time PCR (qPCR) was utilized to compare the expression profiles of these GOIs within diseased tissues (visible lesions), tissues that precede visible lesions by 2–4 cm (transition area), and tissues from healthy-looking colonies with no signs of disease. Results show there are distinctive differences in the expression profiles of these three GOIs within each tissue examined. Collectively, this small suite of GOIs can provide a molecular “finger print” which is capable of differentiating between infected and uninfected colonies on reefs where CYBD is known to occur.

Contrasting Antibacterial Capabilities of the Surface Mucus Layer From Three Symbiotic Cnidarians

“…These results are in agreement with studies on Acropora millepora affected with white syndrome that detected more phenoloxidase activity near the lesion (Palmer et al, 2011). In addition, the healthy-looking tissue of diseased colonies of Orbicella faveolata affected by yellow band disease was shown to have an active immune response (Weil et al, 2009;Morgan et al, 2015). Concurring with previous reports (Fleming, 1922;Ritchie, 2006;Abbas et al, 2007), we were able to detect an innate immune activity in the mucus layer, suggesting that corals expel molecules with such activity from their tissues.…”

The cellular stress response of the scleractinian coral Goniopora columna during the progression of the black band disease

“…For this reason, novel approaches and diagnostic tools have recently substantially increased to assist in the early detection and characterization of such diseases (Pollock et al 2011;Anderson et al 2013Anderson et al , 2016Morgan et al 2015;Fuess et al 2016). However, the knowledge of the cellular mechanisms used by corals to counteract infections remains still limited and the cellular stress response associated with coral diseases has up to now represented an under-studied area of the coral physiology.…”

Caribbean yellow band disease compromises the activity of catalase and glutathione S-transferase in the reef-building coral Orbicella faveolata exposed to anthracene

“…Thus, it is conceivable that anthracene could be inducing damage to the zooxanthellae associated with healthy and diseased O. faveolata, compromising the enzymatic responses or reducing its synthesis in both healthy and CYBDaffected tissues exposed to high doses of this PAH. Such compromise is worse in CYBD-affected tissues because of the additional stress this pathology imposes not only for the zooxanthellae, but also for the coral holobiont (Mydlarz et al 2009, Guerra et al 2014, Morgan et al 2015. This hypothesis, along with the underlying cellular mechanisms involved, remains to be formally tested.…”

“…This disease produces rapid and extensive mortality of living tissues of its hosts, but more importantly, reduces fecundity ), causes structural damage and energetically compromises the zooxanthellae (Cervino et al 2001, Morgan et al 2015. It also alters the gross composition of tissues by decreasing the ratio of proteins and carbohydrates in relation to the amount of lipids in CYBD lesions (Guerra et al 2014).…”