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Genome Sequencing of Evolved Aspergilli Populations Reveals Robust Genomes, Transversions in A. flavus, and Sexual Aberrancy in Non-Homologous End-Joining Mutants

Summary

This research examined how stable the genetic material is in different species of Aspergillus fungi, which are widely used in industrial biotechnology. The study found that these fungi have remarkably stable genomes, even more stable than yeasts and bacteria commonly used in industry. This is important because genetic stability is crucial for consistent industrial production of valuable compounds. Impacts on everyday life: • More reliable and efficient production of industrial products like enzymes, organic acids and pharmaceuticals • Safer use of engineered fungi in biotechnology applications • Better understanding of how fungi evolve and adapt • Improved methods for genetic modification of industrial fungal strains • More stable production processes leading to more consistent consumer products

Background

Aspergillus species are important fungi widely used in industrial applications and some are clinical pathogens. These multinucleate species are often cultured for many generations in laboratories, which can unknowingly propagate hidden genetic mutations. The genome stability of these organisms and the effects of commonly used non-homologous end-joining (NHEJ) mutations needed to be assessed.

Objective

To study the genome stability of Aspergilli species by using mutation accumulation (MA) lines and whole genome sequencing, particularly examining the effects of NHEJ mutations on genome stability. The study aimed to determine mutation rates and patterns in both wild-type and NHEJ mutant strains of three Aspergillus species.

Results

The study found mutation rates of 4.2 × 10−11 (A. flavus), 1.1 × 10−11 (A. fumigatus) and 4.1 × 10−11 (A. nidulans) per site per mitosis in wild-type strains, indicating very robust genomes. The NHEJ mutant strains showed slightly higher mutation rates but still 5-6 times lower than in yeasts. A. flavus showed an unexpectedly high rate of GC → TA transversions, possibly related to aflatoxin production. In A. nidulans, NHEJ mutation caused interference with sexual reproduction, leading to early cessation of cleistothecia development.

Conclusion

Aspergillus genomes are highly stable, with mutation rates lower than other industrial microorganisms. While NHEJ mutations slightly increase mutation rates, they remain safe enough for biotechnology applications. The study revealed species-specific mutation patterns, particularly in A. flavus, possibly linked to aflatoxin production. The research also uncovered an unexpected role of NHEJ in sexual reproduction in A. nidulans.
  • Published in:BMC Biology,
  • Study Type:Laboratory Experimental Study,
  • Source: 10.1186/s12915-019-0702-0
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