The Genetic Dance Of Corals & Algae

In the very early stages of coral symbiosis—four hours, to be exact—algae induces significant changes in coral gene expression.

AsianScientist (Jun. 28, 2016) – Scientists in Japan and Australia have found that corals undergo changes in gene expression within hours of when algae are introduced. Their results, published in Molecular Ecology, could help scientists better understand the symbiotic relationship between corals and algae.

Corals cannot survive on their own for long; they need algae, which provide approximately 90 percent of the energy that the corals need. This means that their partnership must be preserved to keep the corals healthy.

The only time when the corals do not have an algae symbiont is during the larval stage. When the symbiont is introduced, which happens naturally in the wild, the coral absorbs the algae and the algae continues to live within the coral cells for the remainder of the coral’s life.

Researchers from James Cook University and the Okinawa Institute of Science and Technology Graduate University (OIST) set out to learn more about the symbiotic relationship between coral and algae and how it begins.

“We wanted to investigate the gene expression changes when the symbiosis starts in the coral larvae,” said co-author Dr. Chuya Shinzato, group leader of OIST’s Marine Genomics Unit.

Previously, it was thought that in the time when the algae were introduced to the coral, only minor changes in gene expression occurred. However, using the latest technology in genome analysis, the team discovered that significant changes in gene expression did occur, but these were detected four hours after the first interaction with the symbiont. Past studies had missed this window of gene expression, as they had looked only at 12 and 48 hours after first interaction.

Acropora digitifera coral larvae without a symbiont. Credit: OIST
Acropora digitifera coral larvae without a symbiont. Credit: OIST

“This study succeeds in analyzing the very early stages of coral symbiosis,” Shinzato said. “We saw suppression of the genes related to mitochondrial metabolism and protein synthesis, which means that the metabolism stops working for a short time.”

The team’s findings suggest that the coral has to adapt and react to the introduction of the symbiont, instead of passively accepting the algae.

As sea temperatures rise with climate change, a change of even one or two degrees can destroy the symbiotic relationship and leave the coral without its biggest energy source. This phenomenon, called coral bleaching, is a real threat to coral reef ecosystems. Hence, knowledge gleaned from this study is particularly important for protecting corals.

The article can be found at: Mohamed et al. (2016) The Transcriptomic Response of the Coral Acropora digitifera to a Competent Symbiodinium Strain: the Symbiosome as an Arrested Early Phagosome.


Source: Okinawa Institute of Science and Technology Graduate University; Photo: Kyle Taylor/Flickr/CC.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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