A joint study by the researchers from the Stowers Institute for Medical Research in collaboration with Fred Hutchinson Cancer Research Center identifies an unrivaled genetic survival strategy where genes have a dual role to ensure their transmission to the offspring organisms.
The research appeared in the 2017 issue of the scientific journal named “eLife.” It details how the wtf4 gene can act as both a poison and an antidote for their transmission into the next generation. The respective gene was found in S. kambucha fission yeast and it acts dually to eliminate its competition for survival.
Wtf genes are also called selfish genes. They are parasitic in nature with a sole purpose to survive and spread. In particular, the wtf4 gene is a meiotic drive selfish gene and interferes with the process of Meiosis. Meiosis is the form of cell division in the sex cells, called gametes, like eggs and sperm. The gamete-generating cells contain two copies of chromosomes: one from each parent. However, gametes contain only one copy of each chromosome. Meiosis ensures that each copy is transmitted to the gametes in equal numbers. For example, males possess X and Y chromosome. Thus, they produce 50 percent X-bearing and 50 percent Y-bearing sperm cells after meiosis.
It is interesting to note that when meiotic drive genes are at work, they destroy the gametes that don’t carry the chromosome. In this way, they stack the odds in their favor. For example, a male with a gamete-killing meiotic drive gene on his X chromosome can trigger the killing of the sperm carrying the Y chromosome. This eliminates half of the sperm cells competing to fertilize the egg. Ironically, for selfish genes, this process can lead to infertility.
Wtf genes poison their prey
The research team behind the study discovers that wtf genes potentially poison their prey.
According to the research experts, the strategy employed by the wtf selfish genes is to poison all the developing gametes, but then keep the antidote for themselves. The gametes inheriting the selfish genes are also exposed to the poison. But they don’t succumb to it because of the antidote they possess. Note that the gametes that don’t inherit the selfish gene are destroyed.
In earlier studies, the researchers discovered the actions of multiple independent meiotic drivers in fission yeasts. Nevertheless, they didn’t know the exact responsible genes behind, or how they destroyed gametes that didn’t inherit the genes.
To further their knowledge, the Stowers’ researcher used genetic mapping to reveal the complex landscape of multiple meiotic drive genes on chromosome 3 of S. kambucha.
They discovered that wtf genes made two different RNA messages as follow,
- A short message encoding the poison
- A long message encoding the antidote
The poison protein was tagged green and the antidote protein red. The cells were imaged during meiosis.
In those images, the researchers clearly saw that the poison was everywhere so that every cell was exposed to the poison. On the other hand, the antidote was seen only in the spores that inherited the wtf gene. Thus the gametes lacking the wtf genes died.
As per the research team, the combination of their genetics experiments and imaging studies provide ample evidence. Wtf genes make both poison and antidote. The findings of the study are particularly interesting from an evolutionary perspective.
The wtf genes make a poison that has the potential to kill everything, including them as well. However, having a private antidote is their way of eliminating their competition selectively. The findings may also direct expected discoveries of meiotic drive genes in other organisms.
The findings of the study suggest that meiotic drive systems like wtf genes could potentially be used to eradicate pest populations. Moreover, they can work to facilitate the spread of desirable traits in natural populations.