Tapping-Induced Oxidative Stress Is Associated with Hev b6 Allergen Regulation in Hevea brasiliensis

Natural rubber from Hevea brasiliensis contains allergenic proteins (Hev b allergens) that can cause latex allergy. This study investigated how repeated mechanical wounding during latex harvesting (tapping) influences allergen regulation in clone RRIT251 using transcriptomic, biochemical, and protein-level analyses. RNA-seq revealed that most genes remained transcriptionally stable, whereas a subset exhibited differential expression trends under tapping conditions. Most Hev b allergen genes showed reduced expression, whereas Hev b6 and Hev b11 displayed increased expression. qRT-PCR analysis confirmed significant upregulation of these genes, particularly Hev b6 (approximately 2.3-fold increase). ELISA further demonstrated that Hev b6 accumulated at substantially higher levels in latex (~220 µg/mL) than other Hev b allergens. Gene co-expression and pathway enrichment analyses highlighted plant-pathogen interaction pathways involving reactive oxygen species (ROS), MAPK signaling cascades, and WRKY transcription factors. Biochemical analyses showed that ROS levels were approximately 2.17-fold higher in tapped trees than in untapped controls. Catalase (CAT) activity was also markedly elevated, whereas total superoxide dismutase (T-SOD) activity showed no significant difference between treatments. Together, these findings suggest that tapping-induced mechanical stress is associated with activation of ROS-related defense signaling pathways and prominent accumulation of Hev b6, a defense-associated allergen. This study provides new insights into the relationship between tapping stress, plant defense responses, and latex allergen regulation, and may support future strategies aimed at improving our understanding of allergen regulation while maintaining latex productivity.