Discovery of a virus that kills males “exclusively”

Scientists in Japan have identified a virus that selectively kills males, happens to be heritable, and creates generation after generation of all females.

The discovery in caterpillars, described in the Proceedings of the National Academies of Sciences, is “strong” evidence that “more than one virus has evolved to selectively kill male insects,” said Greg Hirst, a symbiosis specialist at the University of Liverpool in England who was not involved in the study. “. 

This could one day help control the population of disease vectors such as mosquitoes.

“I expect more cases like this will be discovered in the near future,” said Daisuke Kajiyama, a researcher at the National Agricultural and Food Research Organization of Japan and one of the study’s authors.

The virus was found by chance. Misato Terao, a technical researcher at Minami Kyushu University, was leveling a vegetable nursery on campus when she found the parasitic green caterpillars gnawing on the plants. She picked it up and took it to the lab of insect physiologist Yoshinori Shintani.

Shintani decided that the caterpillars — tobacco worms, a type of predator and scourge of Asian agriculture — might be useful for feeding other insects.

By the time he remembered them several days later, he had about 50 adults, and unexpectedly, all of them were female.

Dr. Shintani and his colleague Dr. Kageyama soon realized that the insects carried a “male killer.”

For decades, scientists have known that parasitic microbes, usually bacteria, can take up residence in the jelly-like cytoplasm of insect cells. Through a process that is not well understood, these microbes can be transmitted across generations.

Sometimes these microbial symbionts tamper with the host’s reproduction. “The males are useless” because they cannot help spread the microbe, Dr. Kajiyama said. So the symbiote simply eliminates them. Wolbachia bacteria can prevent the birth of male insects. Other bacteria kill developing males before they hatch.

Shintani’s team found that antibiotics did not stop the male-killing effect on the nursery moth’s offspring, so bacteria could not be responsible. Genetic analysis showed clear signs of the presence of a virus.

Outside experts say the team’s discovery is a sign that the male-killing virus is more common than expected. Hirst said the discovery could have implications for the control of other important agricultural pests to which the tobacco worm is closely related.

Restoration of damaged organs with the help of “shape memory implants”

Scientists at the National Research University of Technology have created biodegradable polymer implants with a shape memory effect that can be tailored to the desired shape during preparation for surgery.

Polina Kovalyova, an engineer at the university’s Scientific Educational Center for Biomedical Engineering, indicated in an interview with the newspaper “Izvestia” that the shape can be miniaturized and then inserted into the body through tiny holes. After the desired position is taken, the new material will straighten on its own and take the programmed shape.

She says: “This effect is due to the structure of the modified material, which under normal conditions, its molecular chains contain identical soft and hard glassy parts. After heating, the soft parts become viscous and fluid, which allows them to be given the desired shape and cooled. When reheated, the soft parts release the stored energy and recover Its original appearance.

According to her, compared to similar metallic materials, shape memory polymers are softer and easier to control. In addition, these polymers are biodegradable when no longer needed.

It should be noted that the basis of the new materials is polyactide, from which the threads used in suturing wounds are made, and it has proven its good compatibility with living tissue.

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