In today’s era—marked by the transition of traditional agriculture toward sustainable, efficient, and eco-friendly practices—peptides are emerging as a pivotal bridge connecting fundamental research with practical field applications. Peptides are small-molecule compounds composed of amino acids, typically comprising fewer than 100 residues. Compared to conventional fertilizers and pesticides, peptides offer distinct advantages, including multifaceted functionality, high efficiency, biodegradability, and minimal ecological risk. Not only are they efficiently absorbed by plants, but they also serve as signaling molecules that precisely regulate plant growth, development, stress tolerance, and defense responses.
The most pivotal role of peptides in plant nutrient management lies in their function as signaling molecules that precisely regulate nutrient uptake and utilization. Research indicates that endogenous plant peptides are extensively involved in the uptake and homeostatic maintenance of elements such as nitrogen, phosphorus, sulfur, and iron. These peptides are capable of sensing nutrient conditions within the soil and transmitting these signals throughout the plant body, thereby activating corresponding transporter proteins and metabolic pathways to achieve the fine-tuning of nutrient absorption.
The role of peptides is particularly prominent in the realm of symbiotic nitrogen fixation. Recent research from the Salk Institute has revealed that a small signaling peptide—designated CLE16—facilitates the symbiotic relationship between plant root systems and arbuscular mycorrhizal fungi. When CLE16 is introduced into the soil, the symbiotic structures of the fungi (known as arbuscules) become more robust and longer-lived, ultimately increasing the abundance of these nutrient-exchange structures within the root system（1）. Even more exciting is the discovery that certain mycorrhizal fungi can themselves produce peptide molecules similar to CLE16, thereby amplifying the symbiotic effect by “mimicking” the plant’s own signals. This molecular dialogue between plants and microbes offers a novel conceptual framework for reducing reliance on chemical fertilizers and restoring the natural symbiotic capabilities of crops.
Furthermore, studies have identified various plant-derived peptides—such as NCR, RALF, and PSK peptides—that play critical regulatory roles in the process of symbiotic nitrogen fixation between legumes and rhizobia. By activating specific signaling pathways, these peptides promote the formation of root nodules and enhance nitrogen-fixation efficiency, thereby reducing the required application of nitrogen fertilizers and lowering the agricultural carbon footprint.
Enhanced Stress Tolerance: Crops’ “Natural Shield”
In natural and agroecological systems, plants frequently face abiotic stresses such as drought, salinity, and heavy metals—factors that severely constrain crop yield and quality. Peptides have demonstrated immense potential in assisting plants to cope with these challenges.
Regarding salt stress, studies have shown that a cyclic dipeptide, cyclo(L-Ala-Gly)—derived from the bacterium *Priestia megaterium*—can significantly alleviate salt-induced damage in plants. Another study revealed that in *Arabidopsis*, cyclo(His-Pro) can reprogram carbon metabolic flux, diverting carbon flow from the glycolysis pathway toward the pentose phosphate pathway. This redirection boosts NADPH production and elevates the NADPH/NADP⁺ ratio, thereby providing the reducing power necessary to fuel the plant’s antioxidant defense system. This mechanism of metabolic regulation opens up new avenues for breeding salt-tolerant crops and for the remediation of saline-alkali soils.（2）（3）
Peptides also play a pivotal role in mitigating heavy metal stress. Research has confirmed that specific peptides can enhance plant tolerance to toxic elements—such as cadmium and arsenic—by employing mechanisms such as chelation and compartmentalization to minimize the damage inflicted by heavy metals on plant cells. This offers a biological solution for the safe utilization of agricultural lands contaminated by heavy metals.
Disease Resistance Mechanisms: Nature’s “Biopesticides”
The disease-fighting function of peptides is currently one of the hottest topics in agricultural research. Antimicrobial peptides (AMPs) derived from plants and microorganisms exhibit broad-spectrum antimicrobial activity, capable of inhibiting the growth of fungi, bacteria, and even insect pests. Based on their structural characteristics, these antimicrobial peptides can be classified into various types, including thionins, defensins, cyclic peptides, and hevein-like peptides.
Thionins were among the first plant antimicrobial peptides to be discovered; their structure is characterized by 6 or 8 cysteine residues forming 3 or 4 disulfide bonds, which endow them with exceptional stability. Thionins primarily function by targeting negatively charged phospholipids on the cell membranes of pathogens; by forming protein-lipid complexes, they disrupt membrane integrity and ultimately lead to cell lysis. Furthermore, thionins can activate signaling pathways mediated by plant hormones—such as salicylic acid and jasmonic acid—thereby synergistically enhancing plant immunity.
Defensins constitute another important class of antimicrobial peptides. A research team at Texas A&M University successfully developed a biocontrol strategy targeting Citrus Greening Disease and Potato Zebra Chip Disease using defensins derived from spinach. Following a single application, treated citrus trees demonstrated an increase in fruit yield of up to 50%, while disease symptoms in treated potato tubers were significantly alleviated. Given that these peptides occur naturally in spinach and have been recognized as safe by the U.S. EPA, they hold immense promise for commercial application.
Beyond their direct antimicrobial effects, certain plant peptides can also serve as endogenous immune elicitors. For instance, AtPep1 is capable of activating the innate immune response in Arabidopsis thaliana, thereby shifting the plant into a state of “alertness.” Lipopeptides derived from endophytic bacteria—such as surfactin, fengycin, and iturin—not only inhibit pathogenic bacteria but also induce the plant to develop Systemic Acquired Resistance (SAR).
Ecological and Economic Benefits: A Win-Win Practice
The adoption of peptide-based fertilizers offers a dual advantage in terms of both environmental impact and cost-effectiveness.
Environmental Friendliness: Peptides are inherently biodegradable and leave no chemical residues. Research confirms that the use of peptide-based fertilizers can reduce the carbon footprint (measured in CO2 equivalents) of tomato cultivation by 5% to 8%, while also lowering the risk of agricultural non-point source pollution.（4）
Enhanced Economic Returns: Although the unit price of certain products may be relatively high, the revenue generated by increased yields far outweighs the associated costs. For instance, in tomato cultivation, the application of peptide-based fertilizers can boost gross revenue by $2,970 to $5,830 per hectare.
Conclusion
The role of peptides in agriculture extends far beyond mere nutritional supplementation. They serve as pivotal signaling molecules—acting as vital links between plants and soil, plants and microorganisms, and plants and their environment—and constitute an essential toolkit for achieving precision, eco-friendly, and high-efficiency agriculture. From regulating nutrient uptake and enhancing stress tolerance to activating immune defenses and serving as substitutes for chemical pesticides, peptides are actively reshaping the technological paradigms of modern agriculture. With the deep integration of synthetic biology, artificial intelligence, and nanotechnology, the application of peptides in agriculture is poised to evolve from being merely “usable” to being truly “optimal,” and from being “costly” to being “economical,” ultimately emerging as one of the core driving forces behind sustainable agricultural development