Transcriptome and Metabolome Analysis Reveals that Heterocyclic Amide Compounds Promote Growth in Tomato and Cucumber by Modulating Endogenous Hormones ​

The development of efficient and eco-friendly microbial biostimulants is essential for sustainable vegetable production. DHPQCA (1,5-dioxo-1,2,3,3a,4,5-hexahydropyrrolo[1,2-a]quinazoline-3a-carboxylic acid) and MeDHPQCA (methyl ester of DHPQCA) are two novel heterocyclic amides isolated from Streptomyces roseoflavus NKZ-259, which significantly promote the growth of tomato (Solanum lycopersicum) and cucumber (Cucumis sativus). However, their molecular mechanisms of action remain largely unclear. Here, we used transcriptome sequencing and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to investigate the effects of 0.05 mg/L DHPQCA and MeDHPQCA on endogenous phytohormone profiles and gene expression in tomato and cucumber seedlings. Our results showed that both compounds extensively remodeled phytohormone homeostasis. In tomato, DHPQCA enhanced jasmonic acid (JA), salicylic acid (SA) and cytokinin contents while suppressing gibberellins (GAs) and abscisic acid (ABA), coordinating growth promotion and stress resistance. MeDHPQCA mainly inhibited GA biosynthesis and strongly activated JA-Ile accumulation, balancing auxin metabolism. In cucumber, DHPQCA markedly increased cytokinins and GA₁ levels but repressed JA-dependent defense pathways. Transcriptomic analysis revealed that DHPQCA activated stress and reproductive growth-related genes, whereas MeDHPQCA specifically upregulated photosynthetic genes. KEGG enrichment confirmed that both compounds regulated plant hormone signal transduction and zeatin biosynthesis pathways. These findings clarify the molecular mechanisms of DHPQCA and MeDHPQCA in regulating plant growth and hormone networks, providing a solid basis for developing these heterocyclic amides as novel biostimulants for sustainable agriculture.