Evaluating stony coral tissue loss disease intervention success through
whole-transcriptome gene expression profiling
Abstract
Stony coral tissue loss disease (SCTLD) remains an unprecedented disease
outbreak due to its high mortality rate and rapid spread throughout
Florida’s Coral Reef and wider Caribbean. A collaborative effort is
underway to evaluate disease intervention strategies that mitigate the
spread of SCTLD across coral colonies and reefs. We conducted an in-situ
experiment in Southeast Florida to assess molecular responses among
SCTLD-affected Montastraea cavernosa pre- and post-application of the
most widely-used intervention method, CoreRx Base 2B with amoxicillin.
Through Tag-Seq gene expression profiling of apparently healthy,
diseased, and treated corals, we identified modulation of metabolomic
and immune pathways following antibiotic treatment. In a complementary
ex-situ disease challenge experiment, we exposed nursery-cultured M.
cavernosa and Orbicella faveolata fragments to SCTLD-affected donor
corals to compare transcriptomic profiles among clonal individuals from
unexposed controls, those exposed and displaying disease signs, and
corals exposed and not displaying disease signs. Suppression of
metabolic functional groups and activation of stress gene pathways as a
result of SCTLD exposure were apparent in both species. Amoxicillin
treatment led to a ‘reversal’ of the majority of gene pathways
implicated in disease response, suggesting potential recovery of corals
following antibiotic application. In addition to increasing our
understanding of molecular responses to SCTLD, we provide resource
managers with transcriptomic evidence that disease interventions with
antibiotics appear to be successful and may help to modulate coral
immune responses to SCTLD. These results contribute to feasibility
assessments of intervention efforts following disease outbreaks and
improved predictions of coral reef health in Southeast Florida.