Enhanced pest resistance and increased phenolic production in maize callus transgenically expressing a maize chalcone isomerase -3 like gene

Authors: Dowd, Patrick; Berhow, Mark; Johnson, Eric

Submitted to: Plant Gene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2018
Publication Date: 1/12/2018
Citation: Dowd, P.F., Berhow, M.A., Johnson, E.T. 2018. Enhanced pest resistance and increased phenolic production in maize callus transgenically expressing a maize chalcone isomerase -3 like gene. Plant Gene. 13:50-55. https://doi.org/10.1016/j.plgene.2018.01.002.

Interpretive Summary: Insects and disease greatly reduce corn yields. Corn ear molds can produce toxins harmful to people and animals, causing hundreds of millions of dollars in losses in the U.S. alone. Plant resistance is an economical means to reduce corn ear damage caused by insects and ear rots, but there continues to be a need to determine what genes are involved in producing resistance. A gene isolated from a chromosome region that was previously associated with ear rot resistance was evaluated for its resistance role. The postulated role for the gene in the literature was to increase production of a specific type of resistance chemicals. When introduced into corn cells, cell clumps that had the gene reduced growth of maize pest caterpillars and representative ear rot fungi compared to cell clumps that did not contain the gene. Enhanced production of an unexpected antifungal compound also occurred; levels were significantly associated with the degree of reduced growth by one species of ear rot fungus. This knowledge can be used to guide breeding for insect and ear rot resistance in crop plants, thereby enhancing yield, quality and safety.

Technical Abstract: Significant losses in maize production are due to damage by insects and ear rot fungi. A gene designated as chalcone-isomerase-like, located in a quantitative trait locus for resistance to Fusarium ear rot fungi, was cloned from a Fusarium ear rot resistant inbred and transgenically expressed in maize callus. Transformants were often more resistant to feeding by the corn earworm and fall armyworm compared to glucuronidase (GUS) callus transformant controls. The transformed callus was also more resistant to colonization by the mycotoxin producing ear rot fungi Fusarium graminearum, Fusarium proliferatum, and Fusarium verticillioides. Chemical analysis unexpectedly indicated increased production of several phenolic compounds, instead of flavonoids, compared to GUS controls. The levels of one of these, a glucosylated ferulic acid, were significantly correlated with the degree of growth inhibition of F. graminearum. The production of phenolic compounds suggests this gene product is behaving as a fatty acid binding protein and enhancing transport of fatty acids involved in the production of jasmonic acid, which can augment the biosynthesis of phenolics. Breeding for enhanced expression of this gene can potentially contribute to resistance to both insects and plant pathogenic fungi, thereby contributing to sustainable production and better quality food.