A widespread bacteria called Wolbachia and a virus that it carries can cause sterility in male insects by hijacking their sperm, preventing them from fertilizing eggs of females that do not have the same combination of bacteria and virus. A new study led by microbiome researchers at Penn State has uncovered how this microbial combination manipulates sperm, which could lead to refined techniques to control populations of agricultural pests and insects that carry diseases like Zika and dengue to humans.
The study published today (March 8) in Science.
“Wolbachia is the most widespread bacteria in animals and lives symbiotically within the reproductive tissues of about 50% of insect species, including some mosquitos and flies,” said Seth Bordenstein, professor of biology and entomology, director of the One Health Microbiome Center at Penn State, and one of the leaders of the research team. “Wolbachia has genes from a virus called prophage WO integrated into its genome. These genes — cifA and cifB — allow the bacteria to remarkably manipulate sperm and quickly spread through an insect population for their own good.”
When a male and female insect that both have Wolbachia mate, they successfully reproduce and pass on the bacteria. But when a male with Wolbachia mates with a female with no Wolbachia, the sperm are rendered lethal to the fertilized eggs, succumbing them to death. This system cunningly increases the proportion of offspring with Wolbachia and the virus in the next generation, because females with the bacteria successfully reproduce more frequently than females without.
This system is being used in several ongoing pilot studies across the world to control insect pests and the harmful viral diseases they carry. For example, to control a population of agricultural or human pests that do not have the bacteria, scientists release males with Wolbachia in order to crash the population.
“One of Wolbachia’s superpowers is that it blocks pathogenic RNA viruses such as Zika, dengue and chikungunya virus, so mosquitos with Wolbachia do not pass these viruses on to people when they bite,” Bordenstein said. “So, releases of both male and female mosquitos with Wolbachia in an area where it isn’t already present leads to replacement of the population with mosquitos that can no longer pass on a viral disease. The World Mosquito Program is now using Wolbachia to control viruses in 11 countries. With this study, we reveal the underlying mechanics of how this process works so we can fine-tune the technique to expand its scope in vector control measures.”
Wolbachia’s prophage WO genes code for proteins that interfere with normal development of sperm cells. These proteins impact a critical transformation during sperm development, when the sperm’s genome is repackaged and the sperm changes from a canoe-shape into a more refined needle-like shape.
“This shape change is incredibly important to the success of sperm, and any interference can impact the sperm’s ability to travel in the female reproductive tract and successfully fertilize the egg,” said Rupinder Kaur, assistant research professor of biology and entomology at Penn State and the other leader of the research team. “The transition is highly conserved in almost everything from insects to humans. Defects in this process can also cause male sterility in humans.”
Click here to read more psu.edu
Photo Credit: penn-state-college-of-agricultural-sciences
Categories: Pennsylvania, Crops