The mitigation mechanism of exogenous pyridoxal-5-phosphate on Pb stress damage in Polygonatum Cyrtonema Hua by multi-omics combined analysis

This study systematically analyzed the effects of pyridoxal-5-phosphate (active form of vitamin B6) treatment and lead (Pb) stress on the physiology, gene expression profile and metabolite content of P. cyrtonema using transcriptomic analysis and plant hormone quantitation. The growth and development of P. cyrtonema were promoted by low concentration Pb stress and by the application of vitamin B6 (VB6). High concentrations of Pb induced stress significantly stimulated the antioxidant oxidase enzyme system, including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and malondialdehyde (MDA) and hydrogen peroxide (H2O2). The accumulation of Pb in P. cyrtonema resulted in rapid chlorophyll degradation and associated cell damage. Exogenous application of pyridoxal-5-phosphate (B6, VB6) significantly alleviated these adverse effects. Vitamin B6 (VB6) application in combination with Pb3 (VB6 + Pb3) enhanced antioxidant enzyme activity, effectively removing the reactive oxygen species to inhibit chlorophyll degradation and Pb accumulation to protect plants. Proline, a soluble protein, and main active components (flavonoid, lignin, polysaccharide, and saponin) were significantly increased in the VB6 + Pb3 treatment group for ensuring plant growth. In addition, VB6 application may activate plant hormone signal transduction, vitamin B6 metabolism, and terpenoid backbone biosynthesis pathways. PcSAUR (small auxin up-regulated RNAs, subcellular localized in the nucleus) can be induced by VB6, which is significantly up-regulated to inhibit the Pb accumulation and alleviate oxidative stress, thereby improving P. cyrtonema’s resistance. This study provides a basis for understanding the response mechanisms of medicinal plants to heavy metal stress and for developing effective abiotic stress mitigation strategies.