A fungus that can cause deadly infection in salamanders and newts has a secret weapon that makes it more dangerous, according to a study led by the University of Exeter. The experts report that a fungus called Batrachochytrium salamandrivorans (Bsal) contains multiple copies of “jumping genes,” which can essentially duplicate themselves.
Jumping genes, known by scientists as transposons, are DNA sequences that move from one location on the genome to another. While possessing repeated parts of DNA can be harmful to an organism, the researchers have found a possible evolutionary advantage of jumping genes in Bsal.
The team found different versions of jumping genes repeated multiple times in the genome of Bsal. Furthermore, the transposons appear to have duplicated another group of genes that play a role in the severity of an infection.
“Bsal and related fungal species infect amphibians worldwide, and have been responsible for more than 90 extinctions,” explained study first author Theresa Wacker.
“Bsal infects the skin of salamanders and newts and causes severe wounds. It emerged in Asia, where many newts and salamanders have some tolerance, but it has spread to Europe and is causing European salamander populations to decline.”
“Using new sequencing technologies, we found that Bsal has undergone a genome expansion compared to related species – that is to say, it now has a bigger genome with more genes and also more of these ‘jumping gene’ transposons.”
The experts determined that the ability of jumping genes to “copy and paste” themselves has contributed to the expansion of the Bsal genome.
“If you think of an organism’s genome as a blueprint, transposons are like having many identical pages,” said Wacker. “And sometimes, during the process of copying and pasting, other parts of the book are also copied.”
“It appears that this copying and pasting caused by repetitive jumping gene transposons has also amplified some skin-destroying genes. Having more of these skin-destruction genes allow the fungus to destroy the skin of salamanders more quickly, making it more deadly.”
Study senior author Dr. Rhys Farrer noted that this kind of gene repetition is probably more widespread in nature than we currently realize. “If, as appears to be the case, it confers an evolutionary advantage for the pathogen by making it more virulent, it’s not clear why this isn’t much more common.”
The study is published in the journal Proceedings of the National Academy of Sciences.
Image Credit: Jaime Bosch
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