Aboveground herbivory influences belowground defense responses in maize

Authors: PINGAULT, LISE - University Of Nebraska; BASU, SAUMIK - University Of Nebraska; ZOGLI, PRINCE - University Of Nebraska; Williams, William; Palmer, Nathan - Nate; Sarath, Gautam; LOUIS, JOE - University Of Nebraska

Submitted to: Frontiers in Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Corn is a major crop for U.S., whose production is negatively impacted by insect pests. The European corn borer (ECB) is responsible for major crop losses in corn, and it is known as the "billion dollar bug". Western corn rootworm (WCR) is another damaging pest of corn. How aboveground feeding by ECB affects root physiology and WCR infestation was investigated using a maize inbred line Mp708. ECB larvae were allowed to feed on Mp708 plants for 24 hours and roots were then infested with WCR larvae. Both ECB and WCR larvae were removed and weighed after a period of time in order compare them with larvae that fed on plants not subjected to ECB herbivory. ECB-feeding reduced the weight of WCR larvae that indicated signals emerging from the shoots changed root physiology. Root gene expression profiles were significantly modified after 24 hours of ECB feeding on the shoots. Genes associated with hormonal and metabolite pathways were altered. Uncovering mechanisms of insect resistance in corn will allow breeders to generate more resilient hybrids.

Technical Abstract: The European corn borer (ECB; Ostrinia nubilalis) is an economically damaging insect pest of maize (Zea mays L.), an important cereal crop widely grown globally. Among inbred lines, the maize genotype Mp708 has shown resistance to diverse herbivorous insects, although several aspects of the defense mechanisms of Mp708 plants are yet to be explored. Here, the changes in root physiology arising from short-term feeding by ECB on the shoot tissues of Mp708 plants was evaluated directly using transcriptomics, and indirectly by observing growth of western corn rootworm (WCR; Diabrotica virgifera virgifera) larvae. Mp708 defense responses negatively impacted both ECB and WCR larval weights providing evidence for changes in root physiology in response to ECB feeding on shoot tissues. There was a significant downregulation of the root transcriptomes following short-term ECB feeding, that included genes needed for direct defense (e.g., proteinase inhibitors or chitinases). Our transcriptomic analysis also revealed specific regulation of the genes involved in hormonal and metabolite pathways in the roots of Mp708 plants subjected to ECB herbivory. These data provide support for the long distance signaling-mediated defense in Mp708 plants, and suggest that altered metabolite profiles of roots in response to ECB feeding of shoots likely negatively impacted WCR growth.