The third eye
For the first time, a three-eyed, sighted creature was created
Scientists from Indiana State University have created a genetically modified dung beetle with a functional third eye. The suppression of a single gene involved in the formation of the insect head led to the development of a complex organ. Article by Zattara et al. Development of functional ectopic compound eyes in scarabaeid beetles by knockdown of orthodenticle published in the journal Proceedings of the National Academy of Sciences.
A picture from the press release of Indiana University biologists create beetle with functional extra eye – VM.
Insect eyes are formed from pluripotent stem cells that can transform into all other cells of the body and are localized in the front of the embryo's head. Results of experiments on fruit flies Drosophila and Khrushchak beetles Tribolium has shown that eye development depends on a network of interacting genes, only a small part of which remains unchanged during evolution. For example, excessive activity of the Pax6/eyeless gene, which functions as a control center for other genes, leads to the appearance of ectopic (that is, additional) eyes in flies and amphibians of the genus Xenopus.
Although ectopic eyes include ommatidia – structural units consisting of photoreceptors and cells conducting an electrical impulse – they are not connected by a nerve to the visual cortex. However, the researchers managed to achieve this connection in the tribes of lamellate beetles Onthophagini and Oniticellini by suppressing the orthodenticle gene using small interfering RNAs (siRNAs).
The orthodenticle (otd) gene encodes a transcription factor, a molecule that connects to DNA and regulates the activity of other genes. In Khrushchaks, it is responsible for the development of photoreceptors, and in fruit flies for the formation of a rhabdome (an element of the retina in faceted eyes) and other structures. The researchers suppressed the formation of a transcription factor at the larval stage by using siRNAs that bind to the matrix RNA, which is an otd product, and lead to its degradation.
Despite the fact that otd is important for the formation of eyes in some insects, its suppression in dung beetles causes the appearance of complex ectopic eyes, which are similar in structure to normal eyes. At the same time, mutant beetles whose normal eyes were removed continued to react to light.
According to scientists, the results of the experiment showed that mutation of even one gene can lead to the appearance of functional structures that may be useful for an individual.
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