inhibition-aspergillus-flavus-growth-aflatoxin-production-transgenic

Inhibition of <em>Aspergillus flavus</em> Growth and Aflatoxin Production in Transgenic Maize Expressing the &#945;-amylase Inhibitor from <em>Lablab purpureus</em> L.

Aflatoxin contamination in food and feed crops is a major challenge worldwide. Aflatoxins, produced by the fungus Aspergillus flavus (A. flavus) are ...

USDA-ARS, Food and Feed Safety Research Unit

Homeobox proteins, a class of well conserved transcription factors, regulate the expression of targeted genes, especially those involved in development. In filamentous fungi, homeobox genes are required for normal conidiogenesis and fruiting body formation. In the present study, we identified eight homeobox () genes in the aflatoxin-producing ascomycete, , and determined their respective role in growth, conidiation and sclerotial production. Disruption of seven of the eight genes had little to no effect on fungal growth and development. However, disruption of the homeobox gene AFLA_069100, designated as , in two morphologically different  strains, CA14 and AF70, resulted in complete loss of production of conidia and sclerotia as well as aflatoxins B₁ and B₂, cyclopiazonic acid and aflatrem. Microscopic examination showed that the Δ mutants did not produce conidiophores. The inability of Δ mutants to produce conidia was related to downregulation of  (bristle) and  (abacus), regulatory genes for conidiophore development. These mutants also had significant downregulation of the aflatoxin pathway biosynthetic genes , ,  and the cluster-specific regulatory gene, . Our results demonstrate that  not only plays a significant role in controlling  development but is also critical for the production of secondary metabolites, such as aflatoxins.

The Aspergillus flavus Homeobox Gene, hbx1, is Required for Development and Aflatoxin Production.

Aspergillus flavus is an opportunistic, saprophytic fungus that infects maize and other fatty acid-rich food and feed crops and produces toxic and carcinogenic secondary metabolites known as aflatoxins. Contamination of maize with aflatoxin poses a serious threat to human health in addition to reducing the crop value leading to a substantial economic loss. Here we report designing a tachyplesin1-derived synthetic peptide AGM182 and testing its antifungal activity both in vitro and in planta. In vitro studies showed a five-fold increase in antifungal activity of AGM182 (vs. tachyplesin1) against A. flavus. Transgenic maize plants expressing AGM182 under maize Ubiquitin-1 promoter were produced through Agrobacterium-mediated transformation. PCR products confirmed integration of the AGM182 gene, while RT-PCR of maize RNA confirmed the presence of AGM182 transcripts. Maize kernel screening assay using a highly aflatoxigenic A. flavus strain (AF70) showed up to 72% reduction in fungal growth in the transgenic AGM182 seeds compared to isogenic negative control seeds. Reduced fungal growth in the AGM182 transgenic seeds resulted in a significant reduction in aflatoxin levels (76-98%). The results presented here show the power of computational and synthetic biology to rationally design and synthesize an antimicrobial peptide against A. flavus that is effective in reducing fungal growth and aflatoxin contamination in an economically important food and feed crop such as maize.

Article	Year
The Aspergillus flavus Homeobox Gene, hbx1, is Required for Development and Aflatoxin Production. Toxins\| PubMed ID: 29023405	2017
Control of Aspergillus flavus growth and aflatoxin production in transgenic maize kernels expressing a tachyplesin-derived synthetic peptide, AGM182. Plant science : an international journal of experimental plant biology\| PubMed ID: 29576068	2018

Rajtilak Majumdar

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