NEW YORK (GenomeWeb) – Plasticity in gene expression enables coral populations to better cope with a new environment, according to a new study.
Researchers from the University of Texas swapped inshore and off shore coral populations to examine how they adapted to local environments. As they reported in Nature Ecology & Evolution this week, their genome-wide gene-expression profiling approach found that inshore coral, which hail from a variable environment, were able to alter their gene expression patterns when moved offshore to resemble those of the local population. This plasticity was also associated with a decreased susceptibility to summer bleaching events, the researchers noted.
However, the researchers also found that coral of offshore origin weren't able to adapt as well to inshore life.
"It is exciting that populations so close together — these reefs are less than five miles apart — can be so different," first author Carly Kenkel, now at the Australian Institute of Marine Science, said in a statement. "We've discovered another way that corals can enhance their temperature tolerance, which may be important in determining their response to climate change."
Kenkel and UT's Mikhail Matz conducted a yearlong reciprocal transplant of mustard hill coral, Porites astreoides, between a variable inshore habitat and a stable offshore habitat. Fifteen colonies from each site were moved to the other. After a year, the researchers collected samples for analysis, including genome-wide gene-expression profiling using TagSeq and gene co-expression network analysis.
Using a discriminant analysis of principal components approach, the research pair was able to differentiate the genome-wide gene expression profiles of the inshore and offshore corals while in their native habitats.
With that as a guide, they then determined the extent to which the genome-wide gene expression profiles of coral changed after they were transplanted. Inshore coral transplanted to the offshore site exhibited greater changes in gene expression than offshore coral transplanted to the inshore site, the researchers reported. They further noted the same trend in Symbiodinium, the intracellular symbiont of coral.
A weighted gene co-expression network analysis of coral host and symbionts uncovered 14 co-expression modules, some of which were up-regulated and others down-regulated at the different sites. The magnitude of the responses appeared to vary between sites, the researchers said, indicating that offshore corals have lower gene expression plasticity.
Functional enrichment analysis of these networks found that there are involved in the differential regulation of environmental stress response (ESR). For one module, the top gene ontology term was for cellular response to stress, while another module's was ribosome biogenesis. This suggested to the researchers that corals transplanted to inshore reefs up-regulated stress response genes, while inshore-origin corals down-regulated ribosome biogenesis, which they noted is a hallmark of ESR.
The researchers also noted that elevated environmental stress response plasticity was associated with lower susceptibility to coral bleaching: offshore coral moved to inshore locales had higher levels of stress-induced bleaching.
Kenkel and Matz added in their paper that understanding how coral populations "adapt or acclimatize to local thermal stress is paramount for predicting the responses of corals to future climate change."