Bioactive Seed Coating with Chitosan-Salicylic Acid Networks Activates Folate Metabolism and Nutritional Fortification in Wheat Seedlings.

The present study engineered a bioactive seed coating based on molecularly optimized chitosan-salicylic acid (SA-CS) networks to fortify folate biosynthesis in wheat seedlings. Among tested phytohormones, salicylic acid (SA) promoted seedling growth, folate accumulation, and antioxidant capacity. Composite coatings were fabricated using chitosan of varying molecular weights; films formulated with 0.3% medium molecular weight chitosan and 0.1% SA (SA-MCS) exhibited moderate water vapor permeability and sustained release, creating a favorable microenvironment for germination. SA-MCS coatings significantly increased total folates from 569.87 to 702.75 μg 100 g-1 DW. Mechanistically, controlled SA delivery upregulated GTP cyclohydrolase 1 (GCH1) and aminodeoxychorismate synthase (ADCS), accelerating metabolic flux into the pterin and para-aminobenzoic acid (pABA) branches. Multiomics analysis revealed coordinated mobilization of carbon units from histidine catabolism and glutamate into one-carbon metabolism, providing structural backbones and methyl groups for folate enrichment. These findings demonstrate SA-CS coatings as an efficient, biodegradable seed delivery platform for eco-friendly folate biofortification.