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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Water Management Research » Research » Publications at this Location » Publication #326197
Title: Nutrient supply and simulated herbivory differentially alter the metabolite pools and the efficacy of the glucosinolate-based defense system in Brassica species

Author
item ALMUZINY, MAKHDORA - Clemson University
item DECKER, CHARLOTTE - Clemson University
item Wang, Dong
item GERARD, PATRICK - Clemson University
item THARAYIL, NISHANTH - Clemson University

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2016
Publication Date: 1/3/2017
Citation: Almuziny, M., Decker, C., Wang, D., Gerard, P., Tharayil, N. 2017. Nutrient supply and simulated herbivory differentially alter the metabolite pools and the efficacy of the glucosinolate-based defense system in Brassica species. Journal of Chemical Ecology. 43:129-142. doi: 10.1007/s10886-016-0811-y.

Interpretive Summary: Plants produce an array of secondary metabolites such as glucosinolate and isothiocyanate when exposed to biotic (e.g., attacks by insects and diseases) and abiotic (e.g., lack of nutrient and water) stresses but mechanisms for the stress compound production are not well understood. Greenhouse and laboratory studies were carried out to determine the impact of low nitrogen or potassium fertilization and a simulated biotic stress on the production of glucosinolate and isothiocyanate in two Brassica species. The research showed an increase in the production of glucosinolate under nitrogen-deficient conditions and simulated herbivory, suggesting that these plants might be well defended against environmental stresses. However, the conversion of the less toxic glucosinolate to more toxic isothiocyanate was hampered under nitrogen-deficiency which implies that if plants are weakened by abiotic stresses they would be more prone to insects and diseases.

Technical Abstract: • Environmental stresses often result in upregulation of defense metabolism in plants. However, the dynamics of nitrogen-containing defense compounds that could be remobilized for maintenance-metabolism is less predictable under stress. Even less known is the impact of nutrient deficiency on the effective deployment of plant defenses, where the deterrence is effected through the metabolic conversion of a less toxic compound to a more potent toxin. • We evaluated the primary metabolism, glucosinolate (GLS) production, the conversion efficiency of GLS to more toxic isothiocyanates (ITC), and the potential activity of myrosinase enzyme (MYR) that mediate this conversion in Brassica juncea and B. nigra as influenced by nutrient availability and simulated herbivory. • In both species, N-deficiency and methyl jasmonate (MeJA) application increased the GLS production, with a concomitant decrease in carbohydrate and amino acid content. In B. juncea, application of MeJA decreased the GLS-to-ITC conversion efficiency under both N and K deficiency. Readiness of deployment of GLS, as measured by the apparent activity of MYR, decreased in both species under stress. • The lower conversion efficiency of native GLS-to-ITC, and the lower potential activity of MYR in both species, despite a greater tissue content of GLS under stress indicates that the GLS-MYR-ITC defense system might be less effective under environmental stress.