Multiple immunity-related genes control susceptibility of Arabidopsis thaliana to the parasitic weed Phelipanche aegyptiaca

Authors: Clarke, Christopher; PARK, SO-YON - Virginia Tech; TUOSTO, ROBERT - Virginia Tech; JIA, XIOYAN - Virginia Tech; MCGOUGH, AMANDA - Virginia Tech; VANMULLEKOM, JEN - Virginia Tech; WESTWOOD, JAMES - Virginia Tech

Submitted to: PeerJ
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2020
Publication Date: 6/8/2020
Citation: Clarke, C.R., Park, S., Tuosto, R., Jia, X., Mcgough, A., Vanmullekom, J., Westwood, J.H. 2020. Multiple immunity-related genes control susceptibility of Arabidopsis thaliana to the parasitic weed Phelipanche aegyptiaca. PeerJ. https://doi.org/10.7717/peerj.9268.
DOI: https://doi.org/10.7717/peerj.9268

Interpretive Summary: Parasitic weeds have historically been studied through the lens of weed management. However, parasitic weeds are more similar to microbial plant pathogens in many ways. Parasitic weeds, like microbial plant pathogens, must interact closely with host plants to extract nutrients and suppress defense responses. We studied the parasitic plant Phelipanche aegyptiaca (broomrape) using the same tools and tactics employed to research better-understood microbial plant pathogens. We identified several key parts of the plant immune system that Phelipanche aegyptiaca must manipulate to parasitize the roots of host plants. We hope to use these results to make directed changes in our identified targets to make plants resistant to parasitization by parasitic weeds. These results will benefit researchers working to understand host:pathogen interactions and develop crop plants resistant to parasitic weeds such as broomrape.

Technical Abstract: Parasitic weeds represent a major threat to agricultural production across the world. Little is known about which host genetic pathways determine compatibility for any host – parasitic plant interaction. We developed a quantitative assay to characterize the growth of the parasitic weed Phelipanche aegyptiaca on 46 mutant lines of the host plant Arabidopsis thaliana to identify host genetic pathways that are essential for susceptibility to the parasite. A. thaliana host plants with mutations in genes involved in jasmonic acid biosynthesis/signaling or the negative regulation of plant immunity were less susceptible to P. aegyptiaca parasitization. In contrast, A. thaliana plants with a mutant allele of the immunity hub gene Pfd6 were more susceptible to parasitization. Quantitative PCR revealed that P. aegyptiaca parasitization leads to transcriptional reprogramming of several hormone signaling pathways, including upregulation of several salicylic acid and jasmonic acid signaling genes, immediately following parasite attachment followed by downr egulation during late stage parasite development. While most tested A. thaliana lines were fully susceptible to P. aegyptiaca parasitization, this work revealed several genetic pathways essential for full susceptibility or resistance to parasitism. Altering these pathways may be a viable approach for limiting host plant susceptibility to parasitism.