Overexpression of a maize (Zea mays) defensin-like gene in maize callus enhances resistance to both insects and fungi

Authors: Dowd, Patrick; Johnson, Eric

Submitted to: AGRI GENE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2018
Publication Date: 7/19/2018
Citation: Dowd, P.F., Johnson, E.T. 2018. Overexpression of a maize (Zea mays) defensin-like gene in maize callus enhances resistance to both insects and fungi. AGRI GENE. 9:16/23. https://doi.org/10.1016/j.aggene.2018.07.003.
DOI: https://doi.org/10.1016/j.aggene.2018.07.003

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 gene produces a protein similar to others previously reported to confer resistance to some fungi. When introduced into corn cells, cell clumps that had the gene were not colonized as heavily by some representative ear rot fungi compared to cell clumps that did not contain the gene, and also reduced growth rates of representative insects that damage corn ears. 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: Identification of genes responsible for pest resistance in maize will assist with breeding attempts to reduce crop losses and hazards due to toxins produced by mold infecting ears. A gene coding for a defensin-like gene was cloned from an inbred reported to be resistant to Fusarium proliferatum and Fusarium verticillioides ear rot, based on its location in a QTL associated with resistance to those and other species of ear rot molds that produce mycotoxins. The gene was expressed transgenically in maize callus and the construct presence confirmed in transformants by PCR analysis and by detection with antibody made to a portion of the protein. Positive transformants were more resistant to corn earworms (Helicoverpa zea) and fall armyworms (Spodoptera fruigperda) as indicated by significantly lower weights compared to control callus expressing a ß–glucuronidase (GUS) gene. Positive transformants also had significantly less visible growth of F. proliferatum and F. verticillioides, but not Fusarium graminearum, than controls. This indicates for the first time a defensin that is active against both insects and fungi, thereby allowing for more effective breeding for resistance to both major classes of pests attacking maize.