Variations in kojic acid production and corn infection among aspergillus flavus isolates suggest a potential role as a virulence factor

Authors: Sweany, Rebecca; Gilbert, Matthew; Carter Wientjes, Carol; Moore, Geromy; Lebar, Matthew

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2024
Publication Date: 12/13/2024
Citation: Sweany, R.R., Gilbert, M.K., Carter Wientjes, C.H., Moore, G.G., Lebar, M.D. 2024. Variations in kojic acid production and corn infection among aspergillus flavus isolates suggest a potential role as a virulence factor. Toxins. 16(12) Article 539. https://doi.org/10.3390/toxins16120539.
DOI: https://doi.org/10.3390/toxins16120539

Interpretive Summary: Contamination of corn with acutely toxic and carcinogenic aflatoxins can result in poisonings and death in humans, livestock, pets and wildlife. Understanding the biology of the causal fungal agent Aspergillus flavus and its non-toxigenic biocontrol counterparts is crucial to devising better strategies to manage and minimize aflatoxin contamination of corn. We characterized the corn and soil populations and biocontrol isolates for their ability to produce kojic acid and colonize corn kernels. Both biocontrol isolates and A. flavus strains more frequently isolated from corn produced higher quantities of this anti-fungal and antioxidant chemical. This research suggests that kojic acid is important for infecting corn, which likely helps biocontrol to be successful in reducing aflatoxin contamination of crops.

Technical Abstract: Kojic acid is a secondary metabolite with strong chelating and antioxidant properties produced by Aspergillus flavus and A. oryzae. The ecological role(s) for kojic acid remains unclear. Previously, a non-aflatoxingenic (non-tox) A. flavus isolate had greater expression of kojic acid than an afla-toxigenic (tox) isolate, which was suggested to alter the redox environment to lower aflatoxin production. Greater antioxidant production of A. flavus non-tox strains should aide colonization of corn kernels. Kojic acid production was measured for several non-tox and aflatoxingenic (tox) isolates from a Louisiana population to assess the potential for kojic acid to aid in biocontrol and corn colonization. Corn kernel colonization/degradation was assessed using ddPCR. All iso-lates produced 60 and 700 times greater kojic acid than aflatoxin and known virulence factor cy-clopiazonic acid, respectively, which varied among sclerotial size categories (large(L) > 400 µm, small(S) < µm and mixed(M) both L and S sclerotia). S isolates produced the least kojic acid. Non-tox isolates were among the highest kojic acid producing isolates, except Af36, K49 and 10-581 produced less kojic acid, similar to S isolates. Greater kojic acid production led to more corn kernel degradation, suggesting a potential role for kojic acid as a virulence factor.