“A cure for the blues”: understanding opsins of the emerald ash borer

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The destruction caused by the emerald ash borer, Agrilus planipennis, is an economic and environmental concern. In the United States alone, the emerald ash borer (EAB) is responsible for killing over 50 million ash trees, which make up a large portion of rural and urban landscapes across the nation. Due to the strength and elasticity of ash wood, it is used in the production of various goods, such as baseball bats, bows, tool handles, and furniture. Additionally, the loss of ash species will disrupt habitat and food resources for wildlife.

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An animated GIF showing the spread of EAB from 2002 to 2014.
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The distribution of EAB as of July 1, 2016.

Currently there is no way to control this pest. Our only hope of saving ash trees is by understanding and stopping this invasive insect. It has been known that beetles lack the short-wavelength-sensitive opsin class, altering the sensitivity of their ability to detect the “blue” region on the light spectrum. It has also been widely observed that these beetles are attracted to purple traps more than other colors. This is due to the evolution of opsins in invertebrates, which has diversified opsin proteins that control how the beetles view color. Researchers at Brigham Young University studied the emerald ash borer to understand the molecular complexity of the UV opsin, a G-protein coupled receptor, gene.

A Next-Generation sequencing approach was used by BYU researchers to sequence all the genes expressed in the beetle’s eye. In all nine of the beetles tested, a short-wavelength-sensitive opsin class was not obtained. It was found that the beetles expressed two copies of the opsin gene in each of the ultraviolet and long-wavelength classes, with the male EAB containing a partial copy of a third long-wavelength-sensitive opsin copy. This duplication and modification, through amino acid substitutions, of the UV opsin gene is believed to an adaptation of EAB to compensate the loss of their short-wavelength-sensitive opsin.

This research provided important knowledge on EAB vision. Since EAB rely on color vision for mate selection and choosing suitable trees to live in, if we develop a strategy to shut down opsins in the beetles, it would cause them to be unable to find mates or homes. Their inability to reproduce would allow wildlife management to manage the infestation, in hopes of saving ash trees. However, we would need to be careful when choosing a method of control in order to make sure we do not cause damage to other wildlife or even the human population.

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EAB opsin gene copy expression in males (left) and females (right).

It was also identified that male EAB have an additional copy of a long-wavelength-sensitive opsin that was expressed in at a very low level in comparison to the other two opsin gene copies. From the study alone, it is unknown what the biological importance of this copy is. Further research should be conducted to determine if this opsin gene copy plays a significant role in the life-cycle and fitness of the EAB, which could prove to be useful in developing another strategy to control EAB. 

 

 

 

News article from Science Daily can be found here.
Original research can be found here.

 

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