Metabolomics by UHPLC-HRMS reveals the impact of heat stress on pathogen-elicited immunity in Maize

Authors: Christensen, Shawn; SANTANA, E'LYSSE - Volunteer; Alborn, Hans; Block, Anna; Chamberlain, Casey

Submitted to: Metabolomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2021
Publication Date: 1/5/2021
Citation: Christensen, S.A.; Santana, E.; Alborn, H.T.; Block, A.K.; Chamberlain, C.A. 2021. Metabolomics by UHPLC-HRMS reveals the impact of heat stress on pathogen-elicited immunity in Maize. Metabolomics. 17:6. https://doi.org/10.1007/s11306-020-01739-2.
DOI: https://doi.org/10.1007/s11306-020-01739-2

Interpretive Summary: Maize is a crop of great economic importance, yet the chemical defenses it produces to guard against biotic (i.e. insect or microbe) and abiotic (i.e. heat, water, or carbon dioxide) threats remain poorly understood. Scientists at the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL investigated the chemical responses of maize to biotic, abiotic,and combinatorial (biotic + abiotic) stress treatments. In conjunction, we performed examinations of disease symptoms to better understand the impact of abiotic stress on the ability of plants to defend themselves against biological threats. Our results showed that heat stress combined with fungal infection can negatively affect crop resistance to disease. This study provides strong evidence for the increasing need to incorporate multiple stress factors into experiments targeting improved stress defense strategies. Future elucidation of the specific genes involved in regulating stress responses will contribute to molecular breeding practices that may help to prevent impending stress factors from hampering crop production.

Technical Abstract: The characterization and improved integration of stress-induced defense is vital for global agriculture, as billions of bushels are lost each year due to biotic and abiotic stress. Studies investigating crop resistance to biotic and abiotic stress have largely focused on plant responses to singular forms of stress and individual biochemical pathways that only partially represent stress responses. Thus, combined biotic and abiotic stress treatments and the global assessment of their elicited metabolic expression remains largely unexplored. In this study, we employed targeted and untargeted metabolomics to investigate the metabolic responses of maize (Zea mays) to both individual and combinatorial stress treatments using heat (abiotic)and Cochliobolus heterostrophus infection (biotic) experiments. Ultra-high-performance liquid chromatography-high-resolution mass spectrometry revealed significant metabolic responses to C. heterostrophus infection and heat stress, and comparative analyses between these individual forms of stress demonstrated differential elicitation between the two global metabolomes. In combinatorial experiments, treatment with heat stress prior to fungal inoculation negatively impacted maize disease resistance against C. heterostrophus, and distinct metabolome separation between combinatorial stressed plants and the non-heat stressed infected controls was observed. Targeted analysis revealed inducible primary and secondary metabolite responses to biotic/abiotic stress, and combinatorial experiments indicated that deficiency in the hydroxycinnamic acid, p-coumaric acid, may lead to the heat-induced susceptibility of maize to C. heterostrophus. Collectively, these findings demonstrate that abiotic stress can predispose crops to more severe disease symptoms, underlining the increasing need to investigate defense chemistry in plants under combinatorial stress.