Maize Transcriptome Reveals Time-Resolved Secrets of Biostimulant Action

Biostimulants have quietly become one of the fastest-growing categories of agricultural inputs, promising to coax more growth and stress resilience out of crops without the heavy footprint of conventional fertilizers. Yet for all their commercial momentum, the molecular mechanics of how these products actually work inside a plant have remained stubbornly opaque. A new study published in PLOS One by Mohsen Hesami, Mohammad Rahbari, and Ron A. Salzman now offers one of the most detailed time-resolved views to date, using RNA sequencing to trace how maize leaves respond, hour by hour, to two distinct biostimulant formulations. The results reveal that biostimulant action is not a single blunt signal but a layered, dynamic conversation between chemistry and genome, one that changes character dramatically between the first hours after application and the following day.

The research team focused on two formulations drawn from a commercial biostimulant platform: fulvic acid alone, designated BLG, and a mixture of fulvic acid with quillaja extract, designated BLGQ. Fulvic acid is a humic substance known for its ability to chelate nutrients and modulate plant metabolism, while quillaja extract, derived from the soapbark tree, is rich in saponins and is often included in biostimulant blends for its surfactant and signaling properties. By comparing these two treatments against untreated controls, the researchers could isolate not only what each formulation does, but what the quillaja component adds to the mixture. Leaf tissue was collected at two carefully chosen time points, three hours and twenty-seven hours after application, capturing what the authors describe as the early signaling phase and the later transcriptional and metabolic adjustment phase of the plant response.

The sequencing data showed that the earliest hours after treatment are anything but quiet. Within three hours, both formulations triggered rapid activation of genes involved in hormone signaling, ion transport, proteostasis, and transcription factor networks, the cellular machinery a plant needs to reprogram itself quickly in response to an external cue. What stood out most was the difference in amplitude: the quillaja-containing mixture, BLGQ, induced broader and stronger transcriptional changes than fulvic acid alone. This suggests that the saponin-rich extract acts as an amplifier of sorts, widening the set of genes that respond and pushing the early signaling cascade harder than the humic component can achieve on its own.

Among the most prominently upregulated genes in that early window were members of several major transcription factor families, including ERF, NAC, C2H2, WRKY, and MYB-related factors. These families are well known to science as master regulators of stress responses, growth, and developmental pathways in plants. ERF factors, for example, sit downstream of ethylene signaling and orchestrate responses to stress and senescence, while WRKY and NAC factors coordinate defenses against pathogens, drought, and other challenges. Their rapid mobilization within three hours indicates that the biostimulant treatments are perceived by maize not as passive nutrition but as genuine biological signals that engage the plant’s own regulatory architecture, priming pathways associated with both stress adaptation and growth promotion.

By twenty-seven hours, the picture had shifted in revealing ways. The fulvic acid treatment, BLG, predominantly reinforced broad metabolic, redox, and transcriptional regulatory networks, consistent with a formulation whose effects radiate outward into general adaptive processes: energy metabolism, oxidative balance, and wide-ranging gene regulation. The quillaja mixture, by contrast, emphasized signaling integration, vesicle trafficking, and secondary metabolism at the later time point. Vesicle trafficking, the cellular logistics system that moves proteins and signaling molecules between compartments, is an intriguing target for biostimulant action, as it underpins cell wall modification, hormone transport, and defense signaling. The secondary metabolism signal hints at the production of specialized compounds that may bolster the plant’s defensive and adaptive chemistry over longer timescales.

The transcription factor analysis added a further layer of nuance, showing that each formulation deploys its own regulatory strategy over time. Fulvic acid sustained the upregulation of MYB-related, NAC, GRAS, and ERF transcription factors across the response window, maintaining pressure on pathways tied to general adaptation. The quillaja mixture took a more surgical approach, selectively balancing upregulation and downregulation of NF-YB, HSF, and bZIP families. This push-and-pull pattern suggests a fine-tuning function, in which the mixture modulates heat shock responses, abiotic stress signaling, and specialized metabolic pathways with greater precision rather than simply turning them up. The authors interpret these contrasting patterns as evidence of stimulus- and time-specific strategies, meaning the plant’s response depends on both what is applied and when you look.

Taken together, the findings reframe how biostimulants should be understood at the molecular level. Rather than acting as generic tonics, these formulations appear to engage distinct, overlapping but separable regulatory programs. The fulvic acid response was associated with broader transcriptional changes in genes involved in general adaptive processes, while the quillaja-containing mixture was associated with more specific signaling and regulatory pathways. For growers and agronomists, this has practical implications: the choice between formulations, and the timing of their application, could be optimized based on which physiological outcome is desired, whether broad metabolic support or targeted signaling priming. For biostimulant developers, the study provides a mechanistic roadmap for designing products with defined molecular targets rather than relying on empirical field trial results alone.

The study also carries a methodological lesson that extends well beyond biostimulants. Had the researchers sampled only a single time point, they would have captured a misleadingly static snapshot and missed the fundamental shift in response character between three and twenty-seven hours. The early phase is dominated by rapid signaling and transcription factor activation, while the later phase reflects downstream metabolic and regulatory consolidation. The authors explicitly underline the importance of time-resolved analyses for understanding plant growth and stress adaptation, a point that applies equally to studies of fertilizers, elicitors, and stress treatments across crop science. Dynamic processes demand dynamic measurement, and this work demonstrates how RNA sequencing at multiple time points can expose the temporal architecture of a plant’s response to agricultural inputs.

Maize, as one of the world’s most important cereal crops and a staple grown across diverse and increasingly unpredictable climates, stands to benefit considerably from this kind of mechanistic insight. As agriculture confronts pressure to reduce synthetic inputs while maintaining yields under heat, drought, and disease stress, biostimulants are likely to play an expanding role, and understanding their molecular modes of action will be essential for credible, effective deployment. This transcriptomic study provides a foundation for that understanding, mapping the temporal layers of biostimulant action in a major crop and showing that the mixture of quillaja extract with fulvic acid is more than the sum of its parts. The next steps for the field will involve connecting these transcriptional signatures to measurable agronomic traits, but the study makes clear that the conversation between biostimulant and plant begins within hours and unfolds along distinct, formulation-specific paths that science is only now beginning to read.

Subject of Research: Temporal transcriptomic responses of maize to fulvic acid and quillaja extract biostimulants

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

Article References: Hesami, M., Rahbari, M., & Salzman, R. A. (2026). Temporal and stimulus-specific transcriptional responses of maize to a biostimulant mixture of quillaja extract and fulvic acid. PLOS One, 21(10), e0360081. https://doi.org/10.1371/journal.pone.0360081

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0360081

Keywords: maize, biostimulants, fulvic acid, quillaja extract, transcriptomics, RNA sequencing, transcription factors, plant stress response, hormone signaling, secondary metabolism, time-resolved gene expression, PLOS One