Agrobacterium-mediated horizontal gene transfer plays a key role in plant evolution, but its extent in embryophytes has remained poorly understood. In a study published in The Plant Journal, an international team including Léon Otten from the Institute of Molecular Plant Biology (IBMP, CNRS, University of Strasbourg) analyzed the genomes of over 14,000 embryophytes, revealing the presence of 2,614 naturally transformed species by Agrobacterium. These plants, known as natural genetically modified organisms (nGMOs), contain T-DNA sequences integrated into their genomes, often derived from soil bacteria such as Agrobacterium tumefaciens or Rhizobium rhizogenes.
The researchers demonstrated that these transfers are not limited to angiosperms but also involve older groups such as mosses (82 species) and ferns (75 species), proving that Agrobacterium can transform non-vascular plants and that these transformations date back to the early stages of land plant evolution. Among the major discoveries, the team identified mini T-DNAs, reduced sequences containing only a single gene, such as the cucumopine synthase (cus) gene. These mini T-DNAs, dominant in mosses and ferns, may represent the oldest forms of T-DNA, as they are not associated with tumor or hairy root formation, unlike the more complex T-DNAs observed in spermatophytes.
The study also shows that these transferred genes, such as those encoding opines (compounds used as nutrient sources by Agrobacterium), are often conserved intact in nGMOs, suggesting they may play a functional role in these plants. For example, in species of the genus Vaccinium (such as blueberries), a 1215-like gene (similar to rolB/rolC) has been present for over 30 million years without loss of functionality.
This study greatly expands our understanding of horizontal gene transfer in plants and opens perspectives for the use of these natural mechanisms in crop improvement. It also reveals that economically important plants, such as coffee, avocado, sugarcane, and strawberry, are nGMOs, which could inspire new strategies for agriculture.
