Scientists Find Gene Set Linked To Coral Bleaching

Warmer waters induce changes in the expression of 292 genes in the symbiotic sea anemone Exaiptasia diaphana, with implications for coral bleaching.

AsianScientist (Jul. 18, 2019) – Researchers in Japan have identified a set of genes responsible for coral bleaching induced by higher ocean temperatures. Their findings are published in the journal G3: Genes, Genomes, Genetics.

Coral reefs are a major reservoir of biodiversity in the sea, and they rely on a stable symbiotic relationship between the host cnidarian animals—including corals and sea anemones—and dinoflagellates comprising mainly marine plankton. Ongoing environmental changes due to global warming can permanently damage this symbiosis, resulting in a phenomenon known as coral bleaching.

In this study, researchers led by Assistant Professor Shinchiro Maruyama at Tohoku University, Japan, carried out transcriptomic analysis on the sea anemone Exaiptasia diaphana to shed light on how increases in ocean temperature may affect stable symbiosis in coral reefs. They found that elevated temperatures caused E. diaphana to shift to a non-symbiotic state. They also observed that the expression levels of 292 genes were dramatically and irreversibly altered in the heat-exposed anemone.

The scientists then divided this set of ‘heat induced bleaching associated’ (HIBA) genes into four major functional groups: transporters, oxidation-reduction, lysosomes and carbohydrate metabolism. They noted that dinoflagellates typically inhabit a lysosome-like structure of the E. diaphana, which suggests that altered HIBA gene expression impairs the function of this lysosome-like structure, eventually leading to the collapse of symbiosis.

Going forward, researchers plan to explore mechanistically how carbohydrate metabolism in lysosomes may be essential to the maintenance of stable symbiosis between E. diaphana and its symbionts.

The article can be found at: Ishii et al. (2019) Global Shifts in Gene Expression Profiles Accompanied with Environmental Changes in Cnidarian-Dinoflagellate Endosymbiosis.


Source: Tohoku University; Photo: Shinichiro Maruyama.
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