Temporal and stimulus-specific transcriptional responses of maize to a biostimulant mixture of quillaja extract and fulvic acid.

Biostimulant-induced responses in plants are dynamic, involving rapid signaling events followed by slower, downstream transcriptional and metabolic adjustments. To characterize the temporal molecular responses of maize to two biostimulant formulations, including fulvic acid (BLG) and mixture of fulvic acid and Quillaja extract (BLGQ), RNA sequencing was performed on leaf tissues collected at two time points representing the early (3 h) and later (27 h) transcriptional responses following biostimulant application. Differential gene expression, functional enrichment, and transcription factor analyses were subsequently conducted to compare the two treatments with untreated controls. Early responses revealed rapid activation of hormone signaling, ion transport, proteostasis, and transcription factor (TF) networks, with BLGQ inducing broader and stronger transcriptional changes compared to BLG. Notably, TF families such as ERF, NAC, C2H2, WRKY, and MYB-related were prominently upregulated, suggesting early transcriptional activation of genes associated withstress, growth, and developmental pathways. Later responses showed that BLG predominantly reinforced broad metabolic, redox, and transcriptional regulatory networks, whereas BLGQ emphasized signaling integration, vesicle trafficking, and secondary metabolism. Differential transcription factor modulation further highlighted stimulus- and time-specific strategies: BLG sustained upregulation of MYB-related, NAC, GRAS, and ERF TFs, while BLGQ selectively balanced upregulation and downregulation of NF-YB, HSF, and bZIP families to fine-tune signaling and specialized pathways. These transcriptomic results suggest that maize responses to biostimulants are highly dynamic and stimulus-specific, with BLG response associated with broader transcriptional changes in genes involved in general adaptive processes, whereas BLGQ response associated with more specific signaling and regulatory pathways. Our results provide transcriptomic insight into the temporal layers of biostimulant action and underline the importance of time-resolved analyses for understanding plant growth and stress adaptation.