• 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.

中文翻译：

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烟草中的 TOC1 在食草胁迫下调节氮的有效分配以防御代谢物。

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  生物钟将植物对环境信号的反应联系起来。植物利用时间信息对食草做出反应，但生物钟成分在这些反应中的许多功能作用及其对适应性的贡献仍然未知。
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  我们研究了中央时钟调节器 TIMING OF CAB EXPRESSION 1 (TOC1) 在田间和温室条件下烟草对专业食草动物Manduca sexta的防御反应中的作用。我们利用¹⁵ N 脉冲标记来量化三种防御化合物池中的氮掺入：咖啡酰腐胺 (CP)、二咖啡酰亚精胺 (DCS) 和尼古丁。
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  在对照条件下，与空载体（EV）相比，CP和DCS中的氮掺入减少，并且irTOC1植物中的尼古丁池增加，但这些差异在模拟食草后被消除。 EV 和 irTOC1 植物之间在尼古丁方面的差异，但在苯酚酰胺产量方面的差异，通过乙烯激动剂 1-甲基环丙烯的处理消除了。通过微嫁接， TOC1对尼古丁的影响被隔离到根部，并且不影响异种移植物在田间条件下的适应性。
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  这些结果表明，生物钟通过平衡代谢昂贵的富氮防御化合物的产生以及调节营养生物量和繁殖之间的资源分配来促进植物的健康。