Chitin Oligosaccharides Enhance Broad-Spectrum Insect Resistance and Promote Growth in <i>Brassica napus</i>

). Multiomics analyses revealed that NACOS activated defense-related pathways, including peroxisome, phenylpropanoid biosynthesis, and glutathione metabolism, as evidenced by enhanced activities of superoxide dismutase, peroxidase, and polyphenol oxidase, as well as the accumulation of defense-related metabolites such as GABA, tannins, and oxalic acid. While inducing robust defense responses, NACOS also upregulated photosynthesis-related pathways, leading to improved photosynthetic rates and markedly promoting plant growth and yield. Our study uncovers a dual-role mechanism of NACOS in balancing defense and growth, providing a theoretical basis and practical strategies for developing oligosaccharide-based biopesticides.