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TOC1 in Nicotiana attenuata regulates efficient allocation of nitrogen to defense metabolites under herbivory stress


Valim, Henrique; Dalton, Heidi; Joo, Youngsung; McGale, Erica; Halitschke, Rayko; Gaquerel, Emmanuel; Baldwin, Ian T; Schuman, Meredith Christine (2020). TOC1 in Nicotiana attenuata regulates efficient allocation of nitrogen to defense metabolites under herbivory stress. New Phytologist, 228(4):1227-1242.

Abstract

The circadian clock contextualizes plant responses to environmental signals. Plants use temporal information to respond to herbivory, but many of the functional roles of circadian clock components in these responses, and their contribution to fitness, remain unknown.

We investigate the role of the central clock regulator TIMING OF CAB EXPRESSION 1 (TOC1) in Nicotiana attenuata's defense responses to the specialist herbivore Manduca sexta under both field and glasshouse conditions. We utilize 15N pulse‐labeling to quantify nitrogen incorporation into pools of three defense compounds: caffeoylputrescine (CP), dicaffeoyl spermidine (DCS) and nicotine.

Nitrogen incorporation was decreased in CP and DCS and increased in nicotine pools in irTOC1 plants compared to empty vector (EV) under control conditions, but these differences were abolished after simulated herbivory. Differences between EV and irTOC1 plants in nicotine, but not phenolamide production, were abolished by treatment with the ethylene agonist 1‐methylcyclopropene. Using micrografting, TOC1's effect on nicotine was isolated to the root and did not affect the fitness of heterografts under field conditions.

These results suggest that the circadian clock contributes to plant fitness by balancing production of metabolically expensive nitrogen‐rich defense compounds and mediating the allocation of resources between vegetative biomass and reproduction.

Abstract

The circadian clock contextualizes plant responses to environmental signals. Plants use temporal information to respond to herbivory, but many of the functional roles of circadian clock components in these responses, and their contribution to fitness, remain unknown.

We investigate the role of the central clock regulator TIMING OF CAB EXPRESSION 1 (TOC1) in Nicotiana attenuata's defense responses to the specialist herbivore Manduca sexta under both field and glasshouse conditions. We utilize 15N pulse‐labeling to quantify nitrogen incorporation into pools of three defense compounds: caffeoylputrescine (CP), dicaffeoyl spermidine (DCS) and nicotine.

Nitrogen incorporation was decreased in CP and DCS and increased in nicotine pools in irTOC1 plants compared to empty vector (EV) under control conditions, but these differences were abolished after simulated herbivory. Differences between EV and irTOC1 plants in nicotine, but not phenolamide production, were abolished by treatment with the ethylene agonist 1‐methylcyclopropene. Using micrografting, TOC1's effect on nicotine was isolated to the root and did not affect the fitness of heterografts under field conditions.

These results suggest that the circadian clock contributes to plant fitness by balancing production of metabolically expensive nitrogen‐rich defense compounds and mediating the allocation of resources between vegetative biomass and reproduction.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Scopus Subject Areas:Life Sciences > Physiology
Life Sciences > Plant Science
Uncontrolled Keywords:Plant Science, Physiology
Language:English
Date:1 November 2020
Deposited On:28 Jan 2021 08:41
Last Modified:29 Jan 2021 21:00
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0028-646X
OA Status:Hybrid
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1111/nph.16784
Project Information:
  • : FunderFP7
  • : Grant ID293926
  • : Project TitleCLOCKWORKGREEN - Ecological performance of arrhythmic plants in nature

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