Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2010
Publication Date: 7/1/2010
Citation: Dowd, P.F., Johnson, E.T., Pinkerton, T.S. 2010. Identification and properties of insect resistance-associated maize anionic peroxidases. Phytochemistry. 71(11-12):1289-1297. DOI: 10.1016/j.phytochem.2010.05.001
Interpretive Summary: Insects cause hundreds of millions of dollars in losses to crops each year and facilitate the production of toxic and carcinogenic mold toxins in corn and other crops. The DNA sequence of an enzyme thought to be involved in insect resistance in corn was found to vary in different corn lines, and these variations appeared to influence the substrate that the enzyme acted upon. When a representative example of the gene for the enzyme was introduced and expressed at high levels in corn tissue, the tissue was more resistant to earworms and fall armyworms compared to control transformed material that did not express that enzyme at high levels. When introduced by breeding or genetic engineering, appropriate forms of this gene and its enzyme product should increase insect resistance in corn, thereby increasing yields, reducing the levels of mold toxins, and making the corn safer for humans and animals and more acceptable to importers.
Technical Abstract: Previous studies with transgenic plants have indicated a tobacco anionic peroxidase can confer enhanced resistance to a variety of insects when expressed in different plant species. Tissue that expresses high levels of this enzyme often browns rapidly when damaged. When introduced biolistically, maize callus transformants expressing a maize peroxidase gene with a predicted anionic isoelectric point of about 5.1 produced browner callus compared to a corresponding beta-glucuronidase (GUS) transformant as callus aged. Higher production of only one isozyme of about pI 4.5 was noted. When the callus was fed to two maize pest caterpillar species, growth rates were slower (as reflected by weights) relative to the GUS callus. Based on examination of published information and electrophoretic properties, this gene appears to code for Px11, a peroxidase isozyme that is primarily produced in root tissue and callus. When sequence of the gene in several inbreds was examined, coding variations were noted, despite prior reports that there were no genetic alleles. These coding differences may influence the ability of the peroxidase to promote resistance. This isozyme may function as a natural resistance source to insects, and perhaps disease. In addition to potential use in marker assisted breeding, enhanced expression of this anionic peroxidase through breeding or genetic engineering may lead to enhanced insect or disease resistance.