Genome Mining and Molecular Networking-Targeted Discovery of Siderophores with Plant Growth-Promoting Activities from the Marine-Derived Streptomonospora nanhaiensis 12A09T.

Plant growth regulators (PGRs) significantly contribute to enhancing crop quality and yield. There is an urgent market demand for innovative natural PGRs. Marine natural products have the potential to serve as valuable sources of PGRs. To discover natural siderophore-type PGRs from marine natural products, according to a systematic pipeline for efficient lead-structure discovery from microbial natural products (SPLSD), a unique desferrioxamine-like siderophore biosynthetic gene cluster was discovered and activated by genome mining and culture regulation from a novel species, Streptomonospora nanhaiensis 12A09T. Some potentially new desferrioxamine derivatives were further discovered by the LC-MS/MS molecular network. Three new desferrioxamine derivatives, desferrioxamines C1, C2, and G3 (1-3) and three known ones, terragine E (4) and desferrioxamines E and D2 (5-6), were selectively isolated and identified using chromatography and spectroscopy techniques from S. nanhaiensis 12A09T. In the ferric iron-chelating assay, 4 and 5 showed moderate Fe (III)-complexing capability, compared with desferrioxamine mesylate. In the plant growth-regulatory assay, 1, 5, and 6 potently boosted the root length of Oryza sativa and Brassica campestris seedlings, equivalent to gibberellin. This study reports the first discovery of desferrioxamine derivatives exhibiting plant growth-promoting activity. These findings offer valuable lead compounds for PGRs.