Effect of Galls on the Metabolism of Chrysanthemum Species Based on Metabolomic Profiling

ABSTRACT Introduction Galls, which are abnormal or protruding tissues, form when insects bite plant cells and serve as evidence for understanding plant‐insect interactions. Objectives This study is aimed at understanding the interactions between Chrysanthemum species and insects at the metabolomic level and to reveal the metabolic changes induced by insect galls. Methodology This study employed liquid chromatography–mass spectrometry (LC–MS) and gas chromatography–mass spectrometry (GC–MS), along with multivariate statistics and pathway enrichment, for metabolomic profiling of Chrysanthemum glabriusculum , including gall‐infected and gall‐free leaves, and reported the gall phenomenon in Chrysanthemum species for the first time. Results LC–MS metabolomics analysis identified 105 marker metabolites, with 61 upregulated and 42 downregulated. Organic acids were the most abundant (20.00%), followed by carbohydrates (16.19%) and flavonoids (14.29%). KEGG analysis revealed significant pathway enrichment in flavone and flavonol biosynthesis, the TCA cycle, and galactose metabolism ( p < 0.05). GC–MS metabolomics analysis revealed 27 volatile secondary metabolites, predominantly terpenoids (16 types), followed mainly by alcohol (4 types) and ketone compounds (three types). VIP > 1 analysis revealed 13 differentially signature metabolites; gall tissue (CgCa) presented elevated levels of β‐phellandrene, camphene, and 1,8‐Cineole, whereas γ‐Muurolene, α‐Farnesene, and Copaene were downregulated in CgCa. Conclusions During gall induction, C. glabriusculum plays an important role in energy metabolism through the regulation of key metabolic pathways, such as galactose metabolism and the TCA cycle, and their products; moreover, by regulating the biosynthesis of flavonoids and flavonols and the corresponding accumulation of secondary metabolites (terpenoids, ketones, and alcohols), it defends against insect‐induced galls.