Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2014
Publication Date: 7/2/2014
Citation: Johnson, E.T., Dowd, P.F., Skory, C.D. 2014. Identification of a bioactive Bowman-Birk inhibitor from an insect-resistant early maize inbred. Journal of Agricultural and Food Chemistry. 62(24):5458-5465.
Interpretive Summary: Insects cause billions of dollars of damage to corn and other crops, and also promote contamination of ear molds that produce toxins. Modern corn breeding has developed many inbreds with high yield and superior kernel quality. However, the focus on grain quality may have resulted in the loss of important genetic factors such as insect and disease resistance. Using modern genetic techniques, we have identified novel genes in an inbred developed in Ohio during the 1940s that potentially contributes to higher levels of leaf resistance to fall armyworm and corn earworm caterpillars compared to the parents. These resistance genes include an inhibitor of caterpillar digestion, a protein that inhibits caterpillar protein synthesis, and proteins that likely contribute to the prevention of cell damage during insect chewing. The resistance genes we identified, when incorporated into breeding programs, should result in hybrids with decreased insect and mold damage, leading to more productivity by farmers, a better quality product for end-users and exporters, and a safer product for consumers.
Technical Abstract: Breeding of maize, Zea mays, has improved insect resistance, but the genetic and biochemical basis of many of these improvements is unknown. Maize oligonucleotide microarrays were utilized to identify differentially expressed genes in leaves of three maize inbreds, parents Oh40B and W8 and progeny Oh43, developed in the 1940s. Oh43 had enhanced leaf resistance to corn earworm larvae, Helicoverpa zea, and fall armyworm larvae, Spodoptera frugiperda, compared to one or both parents. Among ca. 100 significantly differentially expressed genes, expression of a Bowman–Birk trypsin inhibitor (BBI) gene was at least ca. 8-fold higher in Oh43 than in either parent. The Oh43 BBI gene was expressed as a recombinant protein. Purified BBI inhibited trypsin and the growth of fall armyworm larvae when added to insect diet. These experiments indicate that comparative gene expression analysis combined with insect resistance measurements of early inbreds can identify previously unrecognized resistance genes.