From Safety to Flavor: Nano-TiO2-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 (nTiO2) 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 nTiO2 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). nTiO2 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.