Nostoc sp. extract enhances rice lodging resistance by remodeling the gene expression network: mechanism and field application

Background Lodging is a major threat to rice production, underscoring the need for sustainable technologies to improve lodging resistance. This study evaluated the potential of cell extracts from several microalgae and cyanobacteria to induce lodging resistance in rice. Results Pot experiments identified the extract from Nostoc sp. SCAU-13 as effective, significantly increasing stem diameter, stem wall thickness, and bending resistance, while reducing the lodging index. Optimization of the extraction method revealed that the aqueous extract (AQE) was the most effective, decreasing the lodging index by 25.2%. Metabolomic analysis showed that AQE is rich in 967 metabolites, notably plant hormones, flavonoids, and lipids. Transcriptomic analysis indicated that AQE treatment significantly altered gene expression in rice stems. Differentially expressed genes were significantly enriched in pathways such as ribosome biogenesis, phenylpropanoid biosynthesis, linoleic acid metabolism, and glutathione metabolism. The resistance mechanism involves remodeling the gene expression network: downregulating defense-related genes to attenuate the “defense alert”; upregulating ribosome synthesis genes and growth regulators to promote protein synthesis and stem reinforcement; and modulating the phenylpropanoid pathway to enhance cell wall lignification. Field trials demonstrated that applying AQE alone reduced the lodging index by 15%. Furthermore, combining AQE with Constrictifilum sp. SCAU-26 increased rice yield even under a 20% reduction in chemical nitrogen fertilizer. Conclusion This study employed multi-omics approaches to elucidate the molecular mechanism by which Nostoc sp. SCAU-13 extract enhances lodging resistance in rice, laying a foundation for the development of green biostimulants derived from cyanobacteria.