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The southern cattle tick (Rhipicephalus microplus) transmits various diseases and can cause significant economic damage to livestock through considerable blood loss in infested cattle. Here, the tick is infected with the microbial fungus Metarhizium anisopliae, which can kill it.
Photo Credit: © Dr Walter O. Beys-da-Silva
Scientific Frontline: Extended "At a Glance" Summary: Starship-Mediated Gene Transfer in Fungal Genomes
The Core Concept: "Starships" are massive mobile genetic elements that actively transport transposable elements (TEs) across different fungal species, driving rapid genetic restructuring and accelerating genome evolution.
Key Distinction/Mechanism: Rather than isolated jumping genes moving solely within a single genome via vertical inheritance, TEs "hitchhike" as cargo within large Starship vectors to cross species barriers horizontally. This cross-species transfer triggers an explosive proliferation of TEs in the recipient fungus, causing drastic structural chromosomal reorganization that can unexpectedly disable the organism's pathogenicity.
Major Frameworks/Components:
- Transposable Elements (TEs): Mobile genetic sequences, often referred to as "jumping genes," capable of altering their position within a host genome.
- Starship Vectors: Large-scale agents of horizontal gene transfer. The research identified that 75 percent of the over 500 Starships examined actively carried TE cargo, indicating a widespread phenomenon in the fungal kingdom.
- Genomic Instability: The rapid, structural reorganization of chromosomes triggered by the massive influx and explosive activity of introduced TEs.
- Pathogenicity Loss: The biological consequence of this genomic instability, wherein beneficial microbial fungi (such as Metarhizium anisopliae) lose their evolutionary adaptations to infect and kill specific target hosts (like the southern cattle tick).
Branch of Science: Evolutionary Biology, Molecular Genetics, Genomics, Mycology, and Agricultural Ecology.
Future Application: Understanding this horizontal transfer mechanism is vital for the commercial development and long-term stability of biological pest control agents. By monitoring or mitigating Starship-mediated genetic instability, agricultural scientists can prevent eco-friendly fungal biopesticides from losing their efficacy against agricultural pests.
Why It Matters: This research reveals a critical evolutionary vulnerability in biological pest control systems. It demonstrates that the host-pathogen "arms race" is not solely dependent on gradual adaptation; massive and rapid horizontal gene transfer can unexpectedly neutralize a beneficial fungus's lethality, fundamentally shifting our understanding of how quickly virulence can degrade in microbial ecosystems.
A new publication from Kiel University shows how the massive exchange of mobile genetic elements between fungi can impair their effectiveness against insects and ticks.
Microbial fungi, such as the genus Metarhizium, are often used in biological pest control. These fungi attack harmful insects and ticks, thus representing an ecological alternative to chemical agents. However, how effective these fungi remain is determined by an evolutionary arms race between the fungus and its host. A research team from Kiel University, together with researchers from Porto Alegre in Brazil, has now discovered that a special mechanism of genome evolution can also reduce the pathogenicity of the fungi.
Starships accelerate genome evolution
Dr Michael Habig's team at Kiel University investigated the role of so-called transposable elements (TEs). These “jumping genes” can change their position in the genome of a species. The researchers found that these TEs use large mobile genetic elements as a means of transport between different fungal species: the so-called Starships. “You can actually imagine this process as a journey in a Starship, with TEs being transported as cargo from one fungal species to another,” explains Habig. The researchers observed an explosive increase in TE activity in the species Metarhizium anisopliae. These TEs had apparently been introduced by a Starship and triggered a drastic structural reorganization of the chromosomes. The study impressively demonstrates that this is not an isolated case: such TE cargo was found in 75 percent of the more than 500 Starships examined - suggesting that Starship-mediated TE-transfer is a widespread phenomenon in the fungal kingdom.
Loss of pathogenicity
This genomic instability has practical implications: While the fungi were highly effective at infecting and killing ticks prior to TE transfer, they lost the ability to infect certain hosts afterwards. "In the case of M. anisopliae, this could mean that the fungus loses its harmful effect on the southern cattle tick. This represents a significant loss for biological pest control," says Habig, a member of the Kiel Evolution Center (KEC).
The recently published study shows that horizontal gene transfer can unexpectedly alter the effectiveness of beneficial fungi – an important finding for the future development of stable biological pest control.
Published in journal: Nature Communications
Title: Transposable elements hitchhike on Starships across fungal genomes
Authors: Hanne Griem-Krey, Júlia de Fraga Sant’Ana, Ursula Oggenfuss, Yohana Porto Calegari-Alves, Ana Luiza Marques, Markus Berger, Lucélia Santi, Walter O. Beys-da-Silva, and Michael Habig
Source/Credit: Kiel University
Reference Number: ebio032326_01
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