All Aboard the Starship: How Fungi Rapidly Evolve in Food and Pathogenic Species

 By: Christine Grace P. Sibayan | Harbinger

Starships are a newly discovered superfamily of gigantic transposable elements found across hundreds of species of fungi. These mobile genetic elements are distinguished from other eukaryotic transposable elements by their remarkable size and complexity.

Unlike typical genes, these massive DNA segments can move between fungal genomes, carrying with them diverse "cargo genes" that provide adaptive traits. Each Starship contains a conserved gene called the Captain (DUF3435), a tyrosine recombinase that enables the entire element to excise and reintegrate into new locations.

Starships are expected to significantly influence various human activities, such as the cultivation and selective breeding of fungi used in cheese production, enhancing fungal resistance to human-made pollutants in the environment, and most strikingly, contributing to the development of new diseases that affect plants. Through laboratory experiments that successfully demonstrated how a Starship moves within genomes and by pinpointing the specific enzyme that enables this movement, researchers have made a substantial advancement in comprehending how these genetic elements function.

In a groundbreaking study published in Genome Biology and Evolution, researchers examined over 1,600 genomes from two major fungal genera: Penicillium and Aspergillus. These genera include species critical to both food production and human disease. Penicillium species make iconic cheeses like Roquefort and Camembert, while Aspergillus species ferment soy sauce and sake—but both genera also contain dangerous human pathogens.

Through phylogenetic examination and the use of a detection tool called "starfish," scientists quantified Captain genes to serve as an indicator of Starship occurrence across seven separate domestication processes. The findings revealed that every domesticated species exhibited a markedly higher number of Starships compared to their wild counterparts.

For example, cheese-making P. camemberti varieties contained substantially more Starships than their environmental sister species P. palitans. Similarly, clinical strains of A. fumigatus, a major airborne pathogen, harbored more Starships than environmental strains (P = 0.02).

What makes Starships particularly unique is their ability to carry dozens of genes as cargo, which gives them an unprecedented capacity to interact with their fungal hosts as both genetic parasites and mutualists. Starships in cheese fungi carry lactose metabolism genes—essential for thriving in dairy environments. Cured-meat species harbor salt tolerance clusters. Clinical strains contain drug resistance genes. "These fungi are essentially collecting genetic toolkits that help them survive in extreme environments created by humans," the researchers note.

The discovery poses concerns regarding antibiotic resistance and food safety, as these mobile elements could rapidly spread adaptive or traits through fungal populations in agricultural and clinical settings.