Transcriptomic combined with physiology revealed the response mechanism of Setaria Italica L. to different mo concentrations

Molybdenum (Mo), an essential micronutrient for plant physiology, impacts plant growth by regulating physiological activities, modulating gene expression, and altering metabolite content. However, the molecular mechanisms underlying plant responses to Mo remain poorly characterized. In this study, low concentrations of Mo increased the growth of foxtail millet, while high concentrations of Mo suppressed its growth. Consequently, we utilized extensive physiological and biochemical assays, along with molecular investigations, to decipher the response pathways of Setaria italica to varying levels of Mo. Using physiological profiling as a foundation, RNA-seq characterized the transcriptome of foxtail millet exposed to varying Mo levels, uncovering crucial pathways such as phenylpropanoid synthesis, starch metabolism, hormone signaling, and flavonoid and carotenoid metabolism. Results showed that there were more differentially expressed genes (DEGs) at 8 mg L− 1 Mo compared to other concentrations, indicating that foxtail millet had a stronger response at this threshold. Compared to the 8 mg L− 1 treatment, the 15 mg L− 1 treatment inhibited starch and sucrose metabolism while enhancing phenylpropanoid and flavonoid biosynthesis. High Mo levels up-regulated key carotenoid biosynthesis genes (such as 9-cis-epoxycarotenoid dioxygenase 4, NCED4, 9-cis-epoxycarotenoid dioxygenase 5, NCED5, zeta-carotene desaturase, ZDS) and modulated hormone signaling, optimizing starch-sucrose regulation and boosting stress resilience in foxtail millet. In conclusion, these results indicate that upraoptimal Mo affects physiological activity of foxtail millet by carbon and nitrogen cycle imbalance, antioxidant system impairment, and ultimately growth suppression, thereby delineating key regulatory nodes in response to Mo in foxtail millet.They improve our understanding of the molecular mechanism of foxtail millet response to Mo, providing some insights into Mo’s role in crop management, potentially aiding in fertilization strategies for improved resilience and productivity.