Multiple molecular defense strategies in Brachypodium distachyon surmount Hessian fly (Mayetiola destructor) larvae-induced susceptibility for plant survival

Authors: SUBRAMANYAM, SHUBHASHREE - Purdue University; Nemacheck, Jill; HARGARTEN, ANDREA - US Department Of Agriculture (USDA); SARDESAI, NAGESH - Corteva Agriscience; WILLIAMS, CHRISTIE - US Department Of Agriculture (USDA); Schemerhorn, Brandi

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2018
Publication Date: 2/22/2019
Citation: Subramanyam, S., Nemacheck, J.A., Hargarten, A., Sardesai, N., Williams, C.E., Schemerhorn, B.J. 2019. Multiple molecular defense strategies in Brachypodium distachyon surmount Hessian fly (Mayetiola destructor) larvae-induced susceptibility for plant survival. Scientific Reports. 9:2596. https://doi.org/10.1038/s41598-019-39615-2.
DOI: https://doi.org/10.1038/s41598-019-39615-2

Interpretive Summary: Hessian fly is known to be one of the most devastating insect pests in wheat worldwide. Critical to understanding how to defend against this wheat pest, is an understanding of what genes are part of a plant's defense. Wheat has a complex genome, making work and understanding of the gene defense pathways difficult. The purpose of this work was to use Brachypodium, a plant related to wheat, to analyze possible defense genes and gene pathways. Using RNA-sequencing, thousands of Hessian fly-responsive genes were found. Those genes were identified, characterized and analyzed in this work, which will add future efforts to improve resistance.

Technical Abstract: The Hessian fly is a destructive pest of wheat causing severe economic damage. Numerous genes and associated biological pathways have been implicated in defense against Hessian fly. However, due to limited genetic resources, compounded with genome complexity, functional analysis of the candidate genes are challenging in wheat. Physically Brachypodium distachyon (Bd) exhibits nonhost resistance to Hessian fly, and with a small genome size, short life cycle, vast genetic resources and amenability to transformation, it offers an alternate functional genomic model for deciphering plant-Hessian fly interactions. RNA-sequencing was used to reveal thousands of Hessian fly-responsive genes in Bd one, three, and five days after egg hatch. Genes encoding defense proteins, stress-regulating transcription factors, signaling kinases, and secondary metabolites were strongly up-regulated within the first 24 hours of larval feeding indicating an early defense, similar to resistant wheat. Defense was mediated by a hypersensitive response that included necrotic lesions, up-regulated ROS-generating and -scavenging enzymes, and H2O2 production. Suppression of cell wall-associated proteins and increased cell permeability in Bd resembled susceptible wheat. Thus, Bd molecular responses shared similarities to both resistant and susceptible wheat, validating its suitability as a model genome for undertaking functional studies of candidate Hessian fly-responsive genes.