Identification of an orthologous clade of peroxidases that respond to feeding by greenbugs (Schizaphis graminum) in c4 grasses

Authors: Scully, Erin; DONZE-REINER, TERESA - West Chester State University; WANG, HAICHUAN - University Of Nebraska; EICKHOFF, THOMAS - Monsanto Corporation; BAXENDALE, FREDERICK - University Of Nebraska; TWIGG, PAUL - University Of Nebraska; KOVACS, FRANK - University Of Nebraska; HANG-MOSS, TIFFANY - University Of Nebraska; Sattler, Scott; Sarath, Gautam

Submitted to: Functional Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2016
Publication Date: 8/26/2016
Publication URL: https://handle.nal.usda.gov/10113/5491304
Citation: Scully, E.D., Donze-Reiner, T., Wang, H., Eickhoff, T., Baxendale, F., Twigg, P., Kovacs, F., Hang-Moss, T., Sattler, S.E., Sarath, G. 2016. Identification of an orthologous clade of peroxidases that respond to feeding by greenbugs (Schizaphis graminum) in c4 grasses. Functional Plant Biology. 43(12):1134-1148. doi:10.1071/FP16104.

Interpretive Summary: INTERPRETIVE SUMMARY Cereal aphids such as the greenbug can cause significant economic damage to a number of cultivated grasses. Mitigating these losses through identification of resistant plant germplasm has been a focus of study for several breeding programs. Peroxidases are a class of enzymes that are frequently enhanced in plants undergoing aphid infestation, and have been used as reliable markers to assess plant responses to aphid herbivory. However few studies have linked specific peroxidases to a resistance response. In this work, a peroxidase enzyme was identified that was specifically enhanced in a sorghum line resistant to greenbugs. This enzyme was named SbPx-1. The gene coding for SbPx-1 was identified on the sorghum genome, and found to occur alongside several other peroxidase-coding genes. The genomes of switchgrass and foxtail millet were next scanned with the SbPx-1 DNA sequence to discover if similar peroxidases occurred in these two other grasses. A cluster of similar peroxidase genes existed within all three grasses. When infested with greenbugs several of these peroxidase genes were specifically upregulated in all three grasses suggesting that common modes of regulation and response to insect herbivory might exist in these grasses. It is now possible to determine whether some of these specific peroxidases can act as markers for insect resistance across a number of related grasses.

Technical Abstract: Knowledge of specific peroxidases that respond to aphid herbivory is limited in C4 grasses, but could provide targets for improving defence against these pests. A sorghum (Sorghum bicolor (L.) Moench) peroxidase (SbPrx-1; Sobic.002G416700) has been previously linked to biotic stress responses, and was the starting point for this study. Genomic analyses indicated that SbPrx-1 was part of a clade of five closely related peroxidase genes occurring within a ~30 kb region on chromosome 2 of the sorghum genome. Comparison of this ~30-kb region to syntenic regions in switchgrass (Panicum virgatum L.) and foxtail millet (Setaria italica L.) identified similar related clusters of peroxidases. Infestation of a susceptible sorghum cultivar with greenbugs (Shizaphis graminum Rondani) induced three of the five peroxidases. Greenbug infestation of switchgrass and foxtail millet plants showed similar inductions of peroxidases. SbPrx-1 was also induced in response to aphid herbivory in a greenbug-resistant sorghum line, Cargill 607E. These data indicate that this genomic region of C4 grasses could be valuable as a marker to assess potential insect resistance in C4 grasses.