Introduction: Why Plant Hormone Signaling and Metabolism Matter
Plant growth is not driven by hormones alone, nor by metabolism acting in isolation. Instead, plant development depends on a continuous, bidirectional dialogue between plant hormone signaling and metabolism. Hormones guide metabolic pathways, while metabolic intermediates feed back to regulate hormone biosynthesis, transport, and signaling intensity.
This concept has gained strong scientific support following a recent review by Fàbregas et al. (2025) published in Plant Physiology, which systematically analyzed how nine major classes of plant hormones interact with primary and secondary metabolism. Their work highlights that hormone–metabolism crosstalk is not a linear hierarchy, but a highly dynamic regulatory network shaping growth, development, and stress adaptation.
Understanding this network is increasingly important for modern agriculture, especially as nutrient efficiency, abiotic stress tolerance, and sustainable productivity become central challenges.
The Core Principle of Plant Hormone Signaling and Metabolism
A Two-Way Regulatory Network
In classical models, plant hormones were often viewed as top-down regulators that simply “command” metabolic responses. However, current research shows that plant hormone signaling and metabolism influence each other reciprocally.
Hormones reshape metabolic fluxes to supply energy and building blocks for growth or defense. At the same time, metabolites such as sugars, organic acids, and amino acid derivatives modulate hormone biosynthesis, transport, perception, and degradation. This feedback ensures that growth decisions align with the plant’s energetic and nutritional status.
Metabolic Hubs as Integrators
Certain metabolic nodes act as universal integrators. Sugar signaling molecules, tricarboxylic acid (TCA) cycle intermediates, and redox-related metabolites quietly coordinate the trade-off between growth and stress resistance. These hubs allow plants to respond flexibly to fluctuating environmental and nutritional conditions without relying on a single dominant signal.
Growth-Promoting Hormones in Plant Hormone Signaling and Metabolism
Gibberellins: Fueling Growth Through Metabolism
Gibberellins (GAs) are widely recognized as growth accelerators. Their biosynthesis spans plastids, the endoplasmic reticulum, and the cytosol, illustrating how hormone production itself is metabolically integrated.
GAs stimulate glycolysis and the TCA cycle, enhancing sucrose utilization and energy availability for cell elongation, fruit development, and biomass accumulation. They also influence cellulose deposition and pigment synthesis. Importantly, metabolites such as sucrose and 2-oxoglutarate feed back to regulate GA biosynthesis, forming a self-adjusting loop within plant hormone signaling and metabolism.
Auxin: Directional Growth Meets Carbon Allocation
Auxin, primarily indole-3-acetic acid (IAA), is synthesized from tryptophan and transported directionally via PIN proteins. It plays a central role in organ patterning and tropic responses.
From a metabolic perspective, auxin promotes the conversion of sucrose into glycolytic intermediates, supporting energy-intensive processes such as pollen maturation and meristem activity. Conversely, sugar availability and the TOR signaling pathway influence auxin biosynthesis, transport efficiency, and downstream responses, reinforcing the tight coupling between metabolism and hormonal control.
Brassinosteroids: Coordinating Growth and Stress Metabolism
Brassinosteroids (BRs), derived from sterol precursors, function as versatile regulators of plant growth. They reprogram sulfur metabolism and modulate flavonoid biosynthesis, especially under drought conditions.
Metabolic factors such as reactive oxygen species (ROS) and AMP-related enzymes participate in fine-tuning BR signaling activity. This integration allows plants to balance rapid growth with oxidative and environmental stress responses.
Defense and Stress Hormones in Plant Hormone Signaling and Metabolism
Salicylic Acid: Immunity Shaped by Metabolites
Salicylic acid (SA), synthesized via the isochorismate pathway, is a cornerstone of plant immune responses. External SA application elevates ascorbate levels, soluble sugars, and reactive oxygen species, reinforcing defense signaling.
At the same time, metabolites such as ascorbate derivatives and N-hydroxypipecolic acid influence SA accumulation and signaling strength. These feedback loops exemplify how metabolic status can shape immune hormone function.
Abscisic Acid: Metabolic Control of Stress Responses
Abscisic acid (ABA), derived from carotenoids, is central to drought and salinity tolerance. Under stress, ABA promotes the accumulation of osmoprotective metabolites such as proline, helping maintain cellular water balance and energy homeostasis.
Interestingly, metabolic compounds including cysteine and glucose can stimulate ABA biosynthesis or attenuate its signaling, ensuring that stress responses remain proportional to metabolic capacity.
Jasmonates: Linking Defense and Nutrient Status
Jasmonates, including JA and JA-Ile, originate from chloroplast lipid metabolism. They regulate tryptophan-derived pathways and glucosinolate synthesis, strengthening resistance against herbivores.
Nutrient availability, particularly phosphorus and potassium, as well as TOR signaling dynamics, significantly affects jasmonate production and activity. This highlights how nutrient metabolism intersects with hormone-driven defense strategies.
Nutrient Allocation Hormones and Metabolic Feedback
Strigolactones: Nutrient Sensing and Branching Control
Strigolactones (SLs), derived from carotenoids, are relatively recent additions to the hormone family. They integrate nitrogen and phosphorus signals to optimize nutrient acquisition and suppress excessive shoot branching.
However, metabolites such as sucrose and citrate can counteract SL-mediated branching inhibition or disrupt downstream signaling. This flexibility allows plants to adjust architecture according to carbon availability and soil fertility.
Ethylene: Ripening, Sugars, and Stress Tolerance
Ethylene, the only gaseous plant hormone, is synthesized from methionine. It regulates fruit ripening, senescence, and stress responses.
Ethylene modulates sucrose transport and promotes flavonol accumulation, enhancing stress tolerance. Meanwhile, sugars such as glucose and sucrose feed back through signaling pathways to regulate ethylene biosynthesis and sensitivity, ensuring coordinated development.
Cytokinins: Cell Division Governed by Metabolism
Cytokinins (CKs), adenine derivatives, are synthesized through two main pathways. They promote cell division and delay senescence.
CK signaling induces trehalose-6-phosphate accumulation and reshapes sulfur metabolism. Hydrogen sulfide can modify cytokinin-related enzymes post-translationally, accelerating CK degradation and enabling rapid environmental adaptation.
Future Perspectives in Plant Hormone Signaling and Metabolism
Advances in genetically encoded biosensors, spatial metabolomics, and real-time imaging now allow researchers to monitor hormone dynamics with unprecedented precision. Coupled with quantitative modeling and targeted genetic engineering, these tools will enable more precise manipulation of hormone–metabolism networks.
For agriculture, this knowledge opens new opportunities to optimize nutrient efficiency, enhance stress tolerance, and fine-tune growth responses. Rather than forcing plants toward maximal growth, future strategies may focus on harmonizing plant hormone signaling and metabolism to achieve stable yields under variable environmental conditions.
Conclusion
Plants may appear silent, but internally they maintain a sophisticated biochemical conversation. The bidirectional crosstalk between hormone signaling and metabolism lies at the heart of plant life, coordinating growth, defense, and adaptation.
Deciphering this dialogue not only advances fundamental plant science but also provides a robust foundation for crop improvement, stress-resilient cultivation, and sustainable agricultural systems. As research continues to unravel these networks, the ability to guide plant performance through informed nutritional and metabolic strategies will become increasingly precise and impactful.
References
Fàbregas, N., Yoshida, T., & Fernie, A. R. (2025). Bidirectional crosstalk between plant hormone signaling and metabolism. Plant Physiology, kiaf630.
https://doi.org/10.1093/plphys/kiaf630