From Safety to Flavor: Nano-TiO ₂ -MeJA Synergistically Alleviates Cadmium Toxicity and Mediates Terpenoid Reprogramming, and Promotes α-Farnesene Accumulation and Refreshing Aroma

Cadmium (Cd) contamination in Jasminum sambac threatens food safety and aroma quality. We compared titanium dioxide nanoparticle ( n TiO 2 ) and methyl jasmonate (MeJA) effects singly or combined using sensory evaluation, HS-SPME-GC-MS, inductively coupled plasma mass spectrometry (ICP-MS), and transcriptome analysis. Cd stress reduced pleasant floral and fruity notes, increased irritating odors, elevated floral Cd accumulation, and shifted volatiles to defense-related sesquiterpenes (e.g., α-cadinol, γ-/d-cadinene). MeJA enriched α-farnesene, enhancing fresh green attributes. ICP-MS revealed n TiO 2 and MeJA each reduced floral Cd by approximately 50%, while their combination achieved 88.3% reduction. Transcriptomics showed Cd upregulated phenylpropanoid/flavonoid genes ( PAL, 4CL, CHS, DFR, ANS ) and activated ABC transporters and salicylic acid (SA) axis ( NPR1-TGA-PR1 ). n TiO 2 attenuated ABCB and ABCG expression, and MeJA enhanced α-linolenic acid metabolism and jasmonate signaling (via COI1-JAZ-MYC2 ). Weighted gene coexpression network analysis (WGCNA) and gene set enrichment analysis (GSEA) indicated energy, redox, and terpenoid pathways (e.g., TPS4, CYP76A26 ) were involved. This study provides a theoretical basis for synergistic safety and flavor of aromatic crops in heavy-metal-contaminated areas.