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Crown-of-Thorns Starfish Genome Points to Potential Biocontrol Methods

NEW YORK (GenomeWeb) – A research team led by the University of Queensland's Centre for Marine Science have published the genome of the crown-of-thorns starfish, Acanthaster planci.

The team's analysis, published today in Nature, revealed that the animal secretes specific proteins to signal individuals to aggregate in large numbers. Unraveling the species' chemical signaling method gives researchers leads to alternative methods to capture and possibly eliminate these starfish pests.

The crown-of-thorns starfish is a native of the coral reefs in the Indo-Pacific region, where it eats species of fast-growing corals and allows coral diversity to increase. However, these starfish are prolific breeders and can lay up to 65 million eggs in a single spawning season. When its population increases significantly, it has a negative impact on healthy coral reef growth since they are able to eat coral faster than it can grow.

"[The goal of this research was] to use genomics and proteomics [analysis] to come up with leads of how to eliminate this pest starfish," Bernard Degnan, corresponding author and professor in the School of Biological Sciences at the University of Queensland in Brisbane, said in an interview.

Like many other marine invertebrates, crown-of-thorns starfish rely primarily on their chemosensory system to detect environmental signals including those from prey, predators, and conspecifics during reproduction, the researchers wrote in the paper. "Waterborne signals probably guide adults to form aggregations before a synchronized spawning event," they added.

The research team wanted to determine if understanding the genetic mechanism of the chemical signaling could lead them to a better population management strategy. More specifically, they hoped the genomic data would allow them to create protein mimetics that would cause the starfish to aggregate together making it possible to capture and eradicate them more easily, Degnan added.

First the team collected specimen samples from an individual from Australia's Great Barrier Reef and from a coral reef area near Okinawa, Japan. Sequencing and analysis of these genomes revealed that although these two individuals had been collected approximately 5,000 kilometers apart, they were members of the same species.

The researchers also generated transcriptome data by extracting RNA from the same individuals they used to create the genome sequence reads, and created RNA sequences. The researchers used the data derived from genome and transcriptome analysis to create a protein database for the starfish.

Next the researchers collected water samples from an aggregation of individuals in an aquarium. Then they ran used mass spectrometry to analyze these samples, identifying 108 proteins that the starfish secreted that could be mapped back to the original genome reads. Of those, 71 proteins were identified as the ones that were emitted by the starfish when they aggregate together, 14 were secreted by starfish in the presence of a predator, and 23 were emitted under both conditions.

"In addition, 37 proteins are related to known secreted signaling and structural proteins, including 15 ependymin-related proteins (EPDRs), five lectins, and four proteins related to deletions in malignant brain tumors," the researchers wrote. "The detection of 15 EPDRs in the secretome of aggregating [crown-of-thorn starfish] suggest that they potentially have a role in conspecific communication; an additional 11 EPDR genes in the [starfish] genome are also highly expressed, mostly in externally connected organs and tissues."

Degnan noted that this study was the conclusion of phase one of the research into better biocontrol methods for the crown-of-thorns starfish, and that they are now working on actually creating protein mimetics using the data. He added that they are already beginning research into using similar methods to develop biocontrols for another invasive starfish species that is colonizing areas off the cost of New England.

Additionally, he said that this type of genomic and proteomic analysis also holds potential to control biofouling, contamination of pipes and underwater surfaces by organisms such as barnacles and algae.