Maize Silk pH as an Indicator of Resistance to the Corn Earworm (Lepidoptera: Noctuidae)

Byrne, Patrick F.; Darrah, L. L.; Simpson, Kristin B; Keaster, Armon J.; Barry, Boubacar; Zubér, M. S.

doi:10.1093/ee/18.3.356

Cited by 3 publications

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“…Corn earworm resistance is positively correlated with a silk browning phenotype (Byrne et al ., 1989, 1996a), in which the silks turn brown within minutes after wounding or cutting. This browning reaction is under monogenic control and is caused by the oxidation of phenolic compounds (Levings and Stuber, 1971).…”

Section: Introductionmentioning

confidence: 99%

Transformation of maize with the p1 transcription factor directs production of silk maysin, a corn earworm resistance factor, in concordance with a hierarchy of floral organ pigmentation

Cocciolone

Nettleton

Snook

et al. 2005

Plant Biotechnology Journal

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SummaryThe maize p1 gene encodes an R2R3-MYB transcription factor that controls the biosynthesis of red flavonoid pigments in floral tissues of the maize plant. Genetic and quantitative trait locus analyses have also associated the p1 gene with the synthesis of maysin, a flavone glycoside from maize silks that confers natural resistance to corn earworm. Here, we show directly that the p1 gene induces maysin accumulation in silk tissues. Transformation of maize plants that had low or no silk maysin with p1 transgenes elevated silk maysin concentrations to levels sufficient for corn earworm abiosis. The p1 transgenes also conferred red pigment to pericarp, cob, husk and tassel tissues, as expected; however, different subsets of these tissues were pigmented within individual transgenic plants. Statistical analysis shows that the pigmentation patterns observed amongst the p1transgenic plants conform to a hierarchy that is similar to the temporal ordering of floral organ initiation. We propose that the observed hierarchy of pigmentation patterns is conferred by variation due to epigenetic control of the p1 transgenes. The production of plants with improved traits through genetic engineering can depend in large part on the achievement of tight organ-specific expression of the introduced transgenes. Our results demonstrate that the production of transgenic plants using a promoter with well-defined tissue specificity, such as the p1 promoter, can result in unexpected variation in tissue specificity amongst the resulting transgenic plants.

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Section: Introductionmentioning

confidence: 99%

Transformation of maize with the p1 transcription factor directs production of silk maysin, a corn earworm resistance factor, in concordance with a hierarchy of floral organ pigmentation

Cocciolone

Nettleton

Snook

et al. 2005

Plant Biotechnology Journal

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Browning-associated mechanisms of resistance to insects in corn callus tissue

Dowd

Norton

1995

J Chem Ecol

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Callus of the fungus- and insect-resistant corn inbred, Mp313E, of differing ages and degrees of brownness was tested for effects on neonate larvae of the corn earworm,Helicoverpa zea. Older, browner, 8-week-old callus caused significantly higher mortality ofH. zea after two days compared to larvae fed 5-week-old callus (brown or not) or pinto bean diet. Larvae fed on the 5-week-old callus were significantly smaller after nine days compared to those fed on nonbrown callus of the same age. Ferulic acid,p-coumaric acid, and sinapic acid, corn allelochemicals associated with cell walls, were oxidized (produced a brown product) up to 10-fold more rapidly by peroxidase preparations of the brown callus compared to nonbrown callus. Peroxidase isozymes from both types of brown callus separated by conventional gel electrophoresis and isoelectric focusing showed more intense anodic/acidic bands compared to peroxidase isozymes separated from the nonbrown callus. Some additional peroxidase isozymes were also present in the brown callus and were able to oxidize ferulic acid. Conventional extraction techniques for phenolic acids indicated free ferulic acid levels were similar for same-age callus, but somewhat less for older callus; no freep-coumaric acid was detected. For esterified and insoluble-bound phenolic content, the level ofp-coumaric acid was higher than that of ferulic acid and was somewhat greater in insoluble-bound fractions for the old callus compared to the younger callus. Color ratings of aqueous extracts and phenolic acid extract residues indicated much brown material remained, which was proportional in color to the original material. The differential insect response to, and peroxidase activity of, brown vs. nonbrown callus were similar to results previously noted for brown pericarps of corn compared to nonbrown pericarps. This information suggests the peroxidases are contributing to the browning through oxidation of phenolic acids and thereby enhancing resistance to insects.

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Enhanced maize (Zea mays L.) pericarp browning: Associations with insect resistance and involvement of oxidizing enzymes

Dowd

1994

J Chem Ecol

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The kernel pericarp of a maize (Zea mays L.) inbred, Mp313E, that browns rapidly at milk stage when damaged and that is resistant toAspergillus flavus Link and the dusky sap beetleCarpophilus lugubris Murray compared to a susceptible inbred, SC212M, was examined for differing oxidizing enzymes (peroxidases) and their substrate specificity. Additional pericarp enzymes were constitutively produced by the Mp313E inbred compared to the SC212M inbred, as indicated by gel electrophoresis and isoelectric focusing. These enzymes oxidized relevent pericarp substrates such as ferulic acid. Similar results were seen with two varieties of maize containing theCh mutant gene, which brown upon senescence in that enhanced oxidation of ferulic acid was seen in homogenates of browned pericarp compared to that which was cold-shocked and did not brown. Corn powder that was browned by mixing oxidizing enzymes with corn pericarp components ferulic acid and coumaric acid were typically less preferred/more toxic to caterpillars such asHelicoverpa zea (Boddie) and sap beetles such asC. lugubris. Thus, enhanced browning of maize pericarp can promote resistance to insects and is at least partly influenced by the presence of oxidizing enzymes. This mechanism may also promote resistance to maize pathogens, including those that produce mycotoxins.

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Maize Silk pH as an Indicator of Resistance to the Corn Earworm (Lepidoptera: Noctuidae)

Cited by 3 publications

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Transformation of maize with the p1 transcription factor directs production of silk maysin, a corn earworm resistance factor, in concordance with a hierarchy of floral organ pigmentation

Transformation of maize with the p1 transcription factor directs production of silk maysin, a corn earworm resistance factor, in concordance with a hierarchy of floral organ pigmentation

Browning-associated mechanisms of resistance to insects in corn callus tissue

Enhanced maize (Zea mays L.) pericarp browning: Associations with insect resistance and involvement of oxidizing enzymes

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