How eriophyid mites shape metal metabolism in leaf galls on Tilia cordata

Metal metabolism in plant–galler interactions is largely unknown. We hypothesise that themites manipulate metal distribution by sequestration of excessive levels and differential regu-lation of metalloproteins to support the main functions of gall-nutrition, protection and micro-environment. Using the Tilia cordata–eriophyid mites system, we aimed to reveal the role of metals in gallsby investigating their distribution, speciation, gene expression and metabolome profiling. Com-plementary spectroscopy techniques (lXRF and lXANES tomographies, electron paramagneticresonance), histochemical, metabolomic and transcriptomic analyses were employed. Mn was the most abundant micronutrient in the galls. Differential cell-specific Mn accumu-lation (idioblasts vs nutritive tissue) and speciation are essential for its homeostasis. Mn(II)-aquo complex, co-localised with Ca, sequestered in idioblasts, while Mn bound to strongerligands including enzymes accumulated in the nutritive tissue. Zn, Cu and Fe predominatelyaccumulated in the nutritive tissue to support intensive metabolic processes such as secondaryand lipid metabolism, protein N-glycosylation and redox regulation. The slower rate ofredox-sensitive spin probes’ decay in the galls indicated a lower amount of antioxidants thanin the leaf. We reveal essential functions of micronutrients in the galls, supporting the developmentaland chemical changes in the host plant, and the nutrition of the galler.