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Trichoderma is a group of fungi commonly used in industrial enzyme and biofuel production, food manufacturing, agricultural biocontrol, and biofertilizers. Trichoderma species exist as filamentous hyphae and are widely distributed in soil, air, various waters, and plant debris. Their most notable features are high genetic diversity and strong environmental adaptability. Another common characteristic is their tendency to be male or female sterile, making sexual reproduction difficult or impossible, thus relying solely on asexual reproduction through vegetative growth.

This research led by Dr. Ting-Fang Wang, Research Fellow at the Institute of Molecular Biology, Academia Sinica, discovering that the DNA cytosine methyltransferases of Trichoderma reesei have multiple functions in meiosis, including initiating meiosis, promoting DNA recombination between parental homologous chromosomes, and using a specialized epigenetic mechanism to induce genome-wide DNA methylation and cytosine (C)-to-thymine (T) hypermutation. These processes ultimately lead to rapid and extensive increases in genome diversity. Ultra-high genomic diversity can be likened to a double-edged sword; while it can enhance the environmental adaptability of offspring in some cases, more often it results in genome instability, hindering the germination of sexual spores or the normal vegetative growth of new mycelia. Our results suggest that wild Trichoderma species with male or female sterility may maintain genome stability and survival advantages due to their sexual dysfunction.

This work was published on July 18, 2024, in the Nucleic Acids Research. The three co-first authors are Dr. Lavernchy Jovanska, the IMB Postdoctoral Research Fellow, Chung-Hsuan Yao, the IMB Visiting Research Fellow, and IMB Research Assistant Yi-Chen Lin. This study was supported by the Institute of Molecular Biology, and the National Science and Technology Council. [NSTC 111-2311- B-001-MY3 to T.F .W.]