Molecular Arms Race: Tannin Biosynthesis and Laccase-Based Detoxification in the Aphid-Gall System

O_LIPlant-insect coevolution is exemplified by Schlechtendalia chinensis inducing gallnuts with record-breaking hydrolyzable tannin (HT) concentrations of 74.49%--32-fold higher than normal leaves. How do plants achieve this extreme defensive chemistry, and how do aphids survive it? C_LIO_LIWe integrated transcriptomics, heterologous gene validation in Arabidopsis, and enzyme assays to investigate both plant HT biosynthesis and aphid detoxification mechanisms throughout gall development. C_LIO_LIThree key genes--Phosphoglucomutase (PGM), UDP-glucosyltransferase BX9 (BX9), and gallate 1-beta-D-glucosyltransferase (GDG) -- govern HT biosynthesis, with expression patterns closely tracking tannin accumulation dynamics, and GDG as the rate-limiting enzyme. Arabidopsis transformants showed threefold HT increases. Critically, S. chinensis employs specialized laccases rather than tannase for detoxification, with laccase activity exceeding tannase by 20,000-fold. The aphid genome encodes three laccase genes, with Sc-Lac1 expressed in digestive tissues, achieving 39-54% HT degradation. C_LIO_LIThese findings reveal how plants weaponize secondary metabolism while herbivores evolve enzymatic countermeasures. The identified genes enable engineering enhanced defenses or pharmaceutical tannin production, while laccase-based detoxification offers new insights into insect adaptation to chemical defenses. C_LI