Control of Aspergillus flavus growth and aflatoxin production in transgenic maize kernels expressing a tachyplesin-derived synthetic peptide, AGM182

Authors: Rajasekaran, Kanniah - Rajah; SAYLER, RONALD - University Of Arkansas; Sickler, Christine; Majumdar, Raj; JAYNES, JESSE - Tuskegee University; Cary, Jeffrey

Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2018
Publication Date: 2/21/2018
Citation: Rajasekaran, K., Sayler, R.J., Sickler, C.M., Majumdar, R., Jaynes, J.M., Cary, J.W. 2018. Control of Aspergillus flavus growth and aflatoxin production in transgenic maize kernels expressing a tachyplesin-derived synthetic peptide, AGM182. Plant Science. 270:150-156. https://doi.org/10.1016/j.plantsci.2018.02.006.

Interpretive Summary: Plants defend themselves from microbial and insect pests by producing a number of different compounds that are toxic to the invading organism. However these defense mechanisms are often inadequate to protect the plant and need to be supplemented with synthetic, chemical pesticides. We have genetically transformed corn plants by introducing a gene that enables them to produce a small synthetic protein or peptide that has been shown in our laboratory to be toxic to fungal and bacterial plant pathogens. The peptide called AGM 182, modelled after an antimicrobial peptide found in Japanese horseshoe crab, does not harm mammalian cells at the levels required to kill microbial pathogens. We identified corn plants carrying the peptide gene and these plants demonstrated increased resistance to attack by both bacterial and fungal pathogens. In addition to reducing toxins produced by fungi thereby increasing food and feed safety, successful expression of the peptide gene in commercially important varieties of corn and other susceptible crops will increase the export quality and value of the crop. It will also reduce the need for treating the crop with chemical pesticides thereby reducing production costs for farmers. Less dependence on chemical pesticides will also be of benefit to the environment.

Technical Abstract: Aspergillus flavus (A. 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. Transgenic maize plants expressing a tachyplesin-derived synthetic peptide AGM182 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 in vitro as well as in planta to reduce aflatoxin contamination in an economically important food crop like maize.