Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/12/2010
Publication Date: 1/28/2010
Citation: Johnson, E.T., Berhow, M.A., Dowd, P.F. 2010. Constitutive Expression of the Maize Genes B1 and C1 in Transgenic Hi II Maize Results in Differential Tissue Pigmentation and Generates Resistance to Helicoverpa zea. Journal of Agricultural and Food Chemistry. 58(4):2403-2409. Interpretive Summary: Insect damage to crops causes billions of dollars of losses each year. Insect damage also leads to contamination by mold toxins, which also causes losses. New sources of insect resistance, preferably identified from plant sources, would minimize these losses. Pigments produced by some corn plants (e.g., in Indian corn) are thought to protect the tissues from UV sunlight damage and invasive bacteria or fungi. A corn line was genetically transferred with two corn genes that control pigment biosynthesis and was configured to produce pigment in all tissues. Several green plants with colored anthers, but only a few plants with colored leaves were recovered. Tissues with high levels of pigment were more resistant to corn earworm feeding compared to non-colored tissues. The plant resistance may be due to the pigment itself or due to other biochemicals synthesized at high levels together with the pigment, or a combination of both. This study indicates that controlled expression of the 2 pigment-inducing corn genes in some non-seed tissues (e.g., tassel, silk, or husk) may help increase resistance to some pests of corn. This approach is advantageous as the corn’s own genes could be used to combat insect pests, thereby reducing ear mold toxins, which improve the health of animals and people and increase the exportability of U.S. corn.
Technical Abstract: Anthocyanin biosynthesis in maize protects tissues from biotic and abiotic stresses. Constitutive expression of the maize B1 and C1 genes, which induces anthocyanin biosynthesis, resulted in transgenic plants with varied phenotypes. Some colored leaves were substantially resistant to thrips damage while only leaves with the highest levels of cyanidin, the predominant anthocyanidin detected in all colored transgenic tissues, were resistant to corn earworm (CEW) larvae. Colored anthers were resistant to CEW feeding and reductions in CEW growth were significantly correlated to levels of cyanidin in the anthers. Cyanidin chloride and cyanidin-3-glucoside chloride added to insect diet slowed the growth of CEW larvae. Attempts to produce 3’5’-hydroxylated anthocyanins in colored maize with the expression of a petunia F3’5’H hydroxylase gene were unsuccessful.