Research on the Molecular Interaction Mechanism between Plants and Pathogenic Fungi

Antibacterial and antifungal pyrazoles based on different construction strategies

The growing prevalence of microbial infections, and antimicrobial resistance (AMR) stemming from the overuse and misuse of antibiotics, call for novel therapeutic agents, particularly ones targeting resistant microbial strains. Scientists are striving to develop innovative agents to tackle the rising microbial infections and abate the risk of AMR. Pyrazole, a five-membered heterocyclic compound belonging to the azole family, is a versatile scaffold and serves as a core structure in many drugs with antimicrobial and other therapeutic effects. In this review, we have updated pyrazole-based antibacterial and antifungal agents mainly developed between 2016 and 2024, by combining with diverse pharmacophores such as coumarin, thiazole, oxadiazole, isoxazole, indole, etc. Meanwhile, the various strategies (molecular hybridization, bioisosterism, scaffold hopping, multicomponent reactions, and catalyst-free synthesis) for integrating different functional groups with the pyrazole ring are discussed. Additionally, structure-activity relationships of these pyrazole derivatives, i.e., how structural modifications impact their selectivity and therapeutic potential against bacterial and fungal strains, are highlighted. This review provides insights into designing next-generation antimicrobials to combat AMR, and offers valuable perspectives to the scientists working on heterocyclic compounds with diverse bioactivities.

Synthesis and Antifungal Evaluation of Cinnamic Acid-Geraniol Hybrids as Potential Fungicides

Cinnamic acid and geraniol are two well-known antifungal natural products and widely applied in food and cosmetics industries. To discover novel natural product-based fungicide candidates with more potent activity and good ecological compatibility for the management of plant diseases, a series of cinnamic acid-geraniol hybrids were prepared by means of molecular hybridization and their chemical structures were well confirmed by spectral analysis. The antifungal activities of the target compounds against three phytopathogenic fungi Fusarium graminearum, Gaeumannomyces graminis (Sacc.) Arx et Oliver var. tritici (Sacc.) Walker, and Valsa mali were evaluated. Among them, compounds 5 e and 5 f showed the remarkable antifungal activity against G. graminis with the EC50 values of 82.719 and 91.828 μg/mL, respectively; while compounds 5 f and 6 b exhibited the obvious antifungal activity against V. mali. It suggested that compound 5 f can be further optimized for the design of novel broad-spectrum fungicide molecules as the secondary lead compound. In addition, some interesting structure-antifungal activity relationships were obtained. This work will provide some reference and guidance for the further discovery of novel fungicide candidates based on cinnamic acid and geraniol.

A glycosylphosphatidylinositol-anchored protein from Alternaria alternata triggers cell death and negatively modulates immunity responses in chrysanthemum

KEY MESSAGE

Glycosylphosphatidylinositol-anchored protein (GPI-AP) Aa049 works as a key pathogenic factor to assist A. alternata in infecting plants, which is associated with the reactive oxygen species (ROS) pathway. Chrysanthemum black spot disease is a common fungal disease caused by A. alternata, which has severely hindered the development of the chrysanthemum industry. However, there are few reports on pathogenic factors in A. alternata, especially regarding GPI-APs. In this study, we identified a GPI-AP, Aa049, from A. alternata. Bioinformatics predictions suggest the presence of GPI-anchored modification sites at the C-terminus of its amino acid sequence, which is relatively conserved among different Alternaria Nees. Transient overexpression of Aa049 in Nicotiana benthamiana can induce programmed cell death (PCD), and the appearance of necrosis depends on its native signal peptide and GPI-anchored sites. Compared with the wild-type strain, the morphology and growth rate of the colony and mycelia of the ΔAa049-deletion mutants do not change. Still the integrity of the cell wall is damaged, and the virulence of the strain is significantly reduced, indicating that Aa049 plays an essential role as a pathogenic factor in the infection process of A. alternata. Furthermore, the results of quantitative real-time PCR (qRT-PCR) and physiological indicators suggested that the virulence of Aa049 may be exerted through the synthesis and clearance pathways of ROS. This study reveals that GPI-APs in A. alternata can act as virulence factors to aid pathogen invasion, providing a potential target for the development of future biopesticides.

Novel Flavonol Derivatives Containing Quinoxaline: Insights into the Antifungal Mechanism against Sclerotinia sclerotiorum

In this study, 12 pairs of tautomeric flavonol derivatives containing quinoxaline were synthesized. The results of antifungal activity showed that in the enol-keto tautomerism, the target compounds containing keto (YB series) had better inhibitory activity against Sclerotinia sclerotiorum (S.s.) than compounds containing enol (YA series). YB9 showed the strongest antifungal activity against S.s., and the median effective concentration (EC50) value was 1.0 μg/mL, which was better than azoxystrobin (Az, 35.3 μg/mL). In vivo fungal inhibition experiments showed that the protective activity of YB9 against rape leaves was 83.4% at 200 μg/mL, which was superior to that of Az (70.2%). The activity of succinate dehydrogenase and molecular docking results showed that YB9 had a stronger antifungal effect than YA9. The results of oxalic acid content determination showed that YB9 could reduce the pathogenic ability of S.s. Then, the inhibitory effect of YB9 against S.s. was further verified by scanning electron microscopy, fluorescence microscopy, cell membrane permeability, cell content leakage, and malondialdehyde content.

A protein elicitor PeVn1 from Verticillium nonalfalfae HW recognized as a MAMP triggers plant immunity response

Protein elicitors can induce plant systemic resistance to pathogens. The recognition of a potential elicitor activates intracellular signaling events, leading to plant resistance against pathogens. In this study, a novel protein elicitor was isolated from the culture filtrate of Verticillium nonalfalfae and named PeVn1, which can induce cell death in several plant species. The PeVn1 gene was then cloned and expressed in Escherichia coli. The recombinant protein PeVn1 triggers cell death in Nicotiana benthamiana in NbBAK1 and NbSOBIR1 dependent manner. Through bioassay analysis showed that the recombinant PeVn1 induced early defense induction events, such as reactive oxygen species burst, callose deposition and the activation of defense hormone signaling pathways and defense enzyme activities. Moreover, PeVn1 significantly enhanced resistance of Nicotiana benthamiana to Sclerotinia sclerotiorum, Botrytis cinerea and N. benthamiana mosaic virus and tomato to Pseudomonas syringae pv. Tomato DC3000. In conclusion, our study reveals that PeVn1 protein as a microbe-associated molecular pattern can induce plant immune responses, which provides a theoretical basis for the development of novel protein-induced disease resistance agents.

Design, Synthesis, Antifungal Activity, and 3D-QSAR Study of Novel Quinoxaline-2-Oxyacetate Hydrazide

Plant pathogenic fungi pose a major threat to global food security, ecosystem services, and human livelihoods. Effective and broad-spectrum fungicides are needed to combat these pathogens. In this study, a novel antifungal 2-oxyacetate hydrazide quinoxaline scaffold as a simple analogue was designed and synthesized. Their antifungal activities were evaluated against Botrytis cinerea (B. cinerea), Altemaria solani (A. solani), Gibberella zeae (G. zeae), Rhizoctonia solani (R. solani), Colletotrichum orbiculare (C. orbiculare), and Alternaria alternata (A. alternata). These results demonstrated that most compounds exhibited remarkable inhibitory activities and possessed better efficacy than ridylbacterin, such as compound 15 (EC50 = 0.87 μg/mL against G. zeae, EC50 = 1.01 μg/mL against C. orbiculare) and compound 1 (EC50 = 1.54 μg/mL against A. alternata, EC50 = 0.20 μg/mL against R. solani). The 3D-QSAR analysis of quinoxaline-2-oxyacetate hydrazide derivatives has provided new insights into the design and optimization of novel antifungal drug molecules based on quinoxaline.

A glycoside hydrolase 30 protein BpXynC of Bacillus paralicheniformis NMSW12 recognized as A MAMP triggers plant immunity response

Bacillus spp. has been widely used as a biocontrol agent to control plant diseases. However, little is known about mechanisms of the protein MAMP secreted by Bacillus spp. Herein, our study reported a glycoside hydrolase family 30 (GH30) protein, BpXynC, produced by the biocontrol bacteria Bacillus paralicheniformis NMSW12, that can induce cell death in several plant species. The results revealed that the recombinant protein triggers cell death in Nicotiana benthamiana in a BAK1-dependent manner and elicits an early defense response, including ROS burst, activation of MAPK cascades, and upregulation of plant immunity marker genes. BpXynC was also found to be a glucuronoxylanase that exhibits hydrolysis activity on xlyan. Two mutants of BpXynC which lost the glucuronoxylanase activity still retained the elicitor activity. The qRT-PCR results of defense-related genes showed that BpXynC induces plant immunity responses via an SA-mediated pathway. BpXynC and its mutants could induce resistance in N. benthamiana against infection by Sclerotinia sclerotiorum and tobacco mosaic virus (TMV). Furthermore, BpXynC-treated tomato fruits exhibited strong resistance to the infection of Phytophthora capsica. Overall, our study revealed that GH30 protein BpXynC can induce plant immunity response as MAMP, which can be further applied as a biopesticide to control plant diseases.

The mitogen-activated protein kinase module CcSte11-CcSte7-CcPmk1 regulates pathogenicity via the transcription factor CcSte12 in Cytospora chrysosperma

The pathogen Cytospora chrysosperma is the causal agent of poplar canker disease and causes considerable economic losses in China. Mitogen-activated protein kinase (MAPK) cascades play a crucial role in mediating cellular responses and Pmk1-MAPKs are indispensable for pathogenic related processes in plant pathogenic fungi. In previous studies, we demonstrated that the CcPmk1 acts as a core regulator of fungal pathogenicity by modulating a small number of master downstream targets, such as CcSte12. In this study, we identified and characterized two upstream components of CcPmk1: MAPKKK CcSte11 and MAPKK CcSte7. Deletion of CcSte11 and CcSte7, resulted in slowed growth, loss of sporulation and virulence, similar to the defects observed in the CcPmk1 deletion mutant. In addition, CcSte11, CcSte7 and CcPmk1 interact with each other, and the upstream adaptor protein CcSte50 interact with CcSte11 and CcSte7. Moreover, we explored the global regulation network of CcSte12 by transcriptional analysis between CcSte12 deletion mutants and wild-type during the simulated infection process. Two hydrolase activity GO terms (GO:0004553 and GO:0016798) and starch and sucrose metabolism (mgr00500) KEGG pathway were significantly enriched in the down-regulated genes of CcSte12 deletion mutants. In addition, a subset of glycosyl hydrolase genes and putative effector genes were significantly down-regulated in the CcSte12 deletion mutant, which might be important for fungal pathogenicity. Especially, CcSte12 bound to the CcSp84 promoter region containing the TGAAACA motif. Moreover, comparison of CcSte12-regulated genes with CcPmk1-regulated genes revealed 116 overlapping regulated genes in both CcSte12 and CcPmk1, including some virulence-associated genes. Taken together, the protein complexes CcSte11-CcSte7-CcPmk1 receive signals transmitted by upstream CcSte50 and transmit signals to downstream CcSte12, which regulates hydrolase, effectors and other genes to promote virulence. Overall, these results indicate that the CcPmk1-MAPK signaling pathway of C. chrysosperma plays a key role in the pathogenicity.

Evolutionary history of the cytochrome P450s from Colletotrichum species and prediction of their putative functional roles during host-pathogen interactions

The genomes of species belonging to the genus Colletotrichum harbor a substantial number of cytochrome P450 monooxygenases (CYPs) encoded by a broad diversity of gene families. However, the biological role of their CYP complement (CYPome) has not been elucidated. Here, we investigated the putative evolutionary scenarios that occurred during the evolution of the CYPome belonging to the Colletotrichum Graminicola species complex (s.c.) and their biological implications. The study revealed that most of the CYPome gene families belonging to the Graminicola s.c. experienced gene contractions. The reductive evolution resulted in species restricted CYPs are predominant in each CYPome of members from the Graminicola s.c., whereas only 18 families are absolutely conserved among these species. However, members of CYP families displayed a notably different phylogenetic relationship at the tertiary structure level, suggesting a putative convergent evolution scenario. Most of the CYP enzymes of the Graminicola s.c. share redundant functions in secondary metabolite biosynthesis and xenobiotic metabolism. Hence, this current work suggests that the presence of a broad CYPome in the genus Colletotrichum plays a critical role in the optimization of the colonization capability and virulence.

Rational design and identification of novel thiosemicarbazide derivatives as laccase inhibitors

BACKGROUND

Laccase is a key enzyme in the fungal 1,8-dihydroxynaphthalene (DHN) melanin biosynthesis pathway, which is a potential target for the control of pathogenic fungi. In our previous work, compound a2 was found with higher inhibition activity against laccase and antifungal activity than laccase inhibitor PMDD-5Y. The introduction of hydrogen-bonded receptors in the amino part was found to be beneficial in improving laccase inhibitory activity by target-based-biological rational design. In this work, the hydrogen-bonded receptors morpholine and piperazine were introduced for structure optimization to enhancing biological activity.

RESULTS

Enzyme activity tests indicated that all target compounds had inhibitory activity against laccase, and some compounds exhibited better activity against laccase than a2, it was further verified that the introduction of hydrogen-bonded receptors in the amino portion could enhance the laccase inhibitory activity of target compounds. Most compounds showed excellent antifungal activities in vitro. Compound m14 displayed good activity against Magnaporthe oryzae both in vitro and in vivo. The scanning electron microscopy (SEM) analysis showed that the mycelium of M. oryzae treated with m14 were destroyed. Molecular docking revealed the binding mode between laccase and target compounds.

CONCLUSION

Thirty-eight compounds were synthesized and showed good inhibitory activity against laccase, the introduction of morpholine and piperazine in the amino part was beneficial to improve antifungal activity and laccase activity. Further validation of laccase as a potential target for rice blast control, while m14 can be used as a candidate compound for the control of rice blast. © 2023 Society of Chemical Industry.

Interactive effects between the invasive weed Stellera chamaejasme and grass: can arbuscular mycorrhizal fungi and fungal pathogens coregulate interspecific relationships?

The interaction between poisonous weeds and neighboring plants is complex. Poisonous weeds frequently have a competitive advantage in the interaction between poisonous weeds and neighboring plants. Arbuscular mycorrhizal fungi (AMF) and plant pathogenic fungi (PPF) are closely related to the interspecific relationships of plants. However, the role of AMF and PPF between poisonous weeds and neighboring grasses remains unclear. Here, we designed a pot experiment to determine the interspecific relationship between Leymus chinensis and Stellera chamaejasme and the regulation of AMF and PPF. The results showed that interactive effects between L. chinensis and S. chamaejasme significantly inhibited the aboveground growth of both but promoted the underground growth of L. chinensis. As the proportions of S. chamaejasme increased, the total nitrogen content and pH in the rhizosphere soil of L. chinensis were reduced, the soil pH of S. chamaejasme was reduced, and the relative abundance of AMF in the rhizosphere soil of L. chinensis significantly increased and that of S. chamaejasme decreased considerably. The relative abundances of PPF in the rhizosphere soil of both in the mono-cultures were significantly higher than those in the mixed cultures. Structural equation modeling indicated that soil abiotic (pH and N availability) and biotic (AMF and PPF) factors are major drivers explaining the interactive effects between L. chinensis and S. chamaejasme. We provided new evidence for the interspecific interactions between poisonous weeds and neighboring grasses and revealed the regulatory role of AMF and PPF in the interactive effects of both plants. This study will provide a scientific basis for the prevention and control of poisonous weeds and the vegetation restoration of degraded grasslands in the future.

Design, Synthesis and Antifungal Activities of Novel Pyrazole Analogues Containing the Aryl Trifluoromethoxy Group

On the basis of the three-component synthetic methodology developed by us, a total of twenty-six pyrazole compounds bearing aryl OCF3 were designed and synthesized. Their chemical structures were characterized by 1H and 13C nuclear magnetic resonance and high-resolution mass spectrometry. These compounds were evaluated systematically for antifungal activities in vitro against six plant pathogenic fungi by the mycelium growth rate method. Most of the compounds showed some activity against each of the fungi at 100 μg/mL. Compounds 1t and 1v exhibited higher activity against all the tested fungi, and 1v displayed the highest activity against F. graminearum with an EC50 value of 0.0530 μM, which was comparable with commercial pyraclostrobin. Structure-activity relationship analysis showed that, with respect to the R1 substituent, the straight chain or cycloalkyl ring moiety was a key structural moiety for the activity, and the R2 substituent on the pyrazole ring could have significant effects on the activity. Simple and readily available pyrazoles with potent antifungal activity were obtained, which are ready for further elaboration to serve as a pharmacophore in new potential antifungal agents.

Natural products from marine fungi as a source against agricultural pathogenic fungi

There are many kinds of agricultural pathogenic fungi, which may belong to pathogenic fungi in different species, such as Fusarium, Alternaria, Colletotrichum, Phytophthora, and other agricultural pathogens. Pathogenic fungi from different sources are widely distributed in agriculture, which threaten the lives of crops around the world and caused great damage to agricultural production and economic benefits. Due to the particularity of the marine environment, marine-derived fungi could produce natural compounds with unique structures, rich diversities, and significant bioactivities. Since marine natural products with different structural characteristics could inhibit different kinds of agricultural pathogenic fungi, secondary metabolites with antifungal activity could be used as lead compounds against agricultural pathogenic fungi. In order to summarize the structural characteristics of marine natural products against agricultural pathogenic fungi, this review systematically overview the activities against agricultural pathogenic fungi of 198 secondary metabolites from different marine fungal sources. A total of 92 references published from 1998 to 2022 were cited. KEY POINTS: • Pathogenic fungi, which could cause damage to agriculture, were classified. • Structurally diverse antifungal compounds from marine-derived fungi were summarized. • The sources and distributions of these bioactive metabolites were analyzed.

Synthesis, Structure-Activity Relationship, and Mechanism of a Series of Diarylhydrazide Compounds as Potential Antifungal Agents

A series of simple diarylhydrazide derivatives (45 examples) were well-designed, prepared, and screened for their antifungal activities both in vitro and in vivo. Bioassay results suggested that all designed compounds had significant activity against Alternaria brassicae (EC₅₀ = 0.30-8.35 μg/mL). Among of them, 2c, as the highest activity compound, could effectively inhibit the growth of plant pathogens Pyricularia oryza, Fusarium solani, Alternaria solani, Alternaria brassicae, and Alternaria alternate and was more potent than carbendazim and thiabendazole. 2c showed almost 100% protection at 200 μg/mL in vivo activity against A. solani in tomato. Moreover, 2c did not affect the germination of cowpea seed and the growth of normal human hepatocytes. The preliminary mechanistic exploration documented that 2c could result in the abnormal morphology and irregular structure of the cell membrane, destroy the function of mitochondria, increase the reactive oxygen species, and inhibit the proliferation of hypha cell. The above results manifested that target compound 2c could be a potential fungicidal candidate against phytopathogenic diseases for its excellent fungicidal activities.

Membrane Dynamics Regulated by Cytoskeleton in Plant Immunity

The plasma membrane (PM), which is composed of a lipid layer implanted with proteins, has diverse functions in plant responses to environmental triggers. The heterogenous dynamics of lipids and proteins in the plasma membrane play important roles in regulating cellular activities with an intricate pathway that orchestrates reception, signal transduction and appropriate response in the plant immune system. In the process of the plasma membrane participating in defense responses, the cytoskeletal elements have important functions in a variety of ways, including regulation of protein and lipid dynamics as well as vesicle trafficking. In this review, we summarized how the plasma membrane contributed to plant immunity and focused on the dynamic process of cytoskeleton regulation of endocytosis and exocytosis and propose future research directions.

Bioactivity, Uptake, and Distribution of Prothioconazole Loaded on Fluorescent Double-Hollow Shelled Mesoporous Silica in Soybean Plants

Prothioconazole (PTC) has been widely utilized for plant fungal disease control, but its metabolite prothioconazole-desthio (PTC-d) exhibits reproductive toxicity. In the present study, carbon quantum dot (CQD)-modified fluorescent double-hollow shelled mesoporous silica nanoparticles (FL-MSNs) loaded with PTC, referred to as PTC@FL-MSNs, were constructed with an average size of 369 nm and a loading capacity of 28.1 wt %, which could increase the antifungal efficiency of PTC. In addition, upright fluorescence microscope and UPLC-MS/MS studies showed that PTC@FL-MSNs could be effectively transported via root uptake and foliar spray in soybean plants. Compared to a 30% PTC dispersible oil suspension agent, the PTC@FL-MSN treatment group showed higher concentrations (leaves: 0.50 > 0.48 mg/kg), longer half-lives for degradation (leaves: 3.62 > 3.21 d; roots: 3.39 > 2.82 d), and fewer metabolites. These findings suggest that sustained pesticide release and toxicity reduction are potential applications for PTC nanofungicide delivery technology.

Appressoria-Small but Incredibly Powerful Structures in Plant-Pathogen Interactions

Plant-pathogenic fungi are responsible for many of the most severe crop diseases in the world and remain very challenging to control. Improving current protection strategies or designating new measures based on an overall understanding of molecular host-pathogen interaction mechanisms could be helpful for disease management. The attachment and penetration of the plant surface are the most important events among diverse plant-fungi interactions. Fungi evolved as small but incredibly powerful infection structure appressoria to facilitate attachment and penetration. Appressoria are indispensable for many diseases, such as rusts, powdery mildews, and blast diseases, as well as devastating oomycete diseases. Investigation into the formation of plant-pathogen appressoria contributes to improving the understanding of the molecular mechanisms of plant-pathogen interactions. Fungal host attachment is a vital step of fungal pathogenesis. Here, we review recent advances in the molecular mechanisms regulating the formation of appressoria. Additionally, some biocontrol agents were revealed to act on appressorium. The regulation of fungal adhesion during the infective process by acting on appressoria formation is expected to prevent the occurrence of crop disease caused by some pathogenic fungi.

The Cytoskeleton in Plant Immunity: Dynamics, Regulation, and Function

The plant cytoskeleton, consisting of actin filaments and microtubules, is a highly dynamic filamentous framework involved in plant growth, development, and stress responses. Recently, research has demonstrated that the plant cytoskeleton undergoes rapid remodeling upon sensing pathogen attacks, coordinating the formation of microdomain immune complexes, the dynamic and turnover of pattern-recognizing receptors (PRRs), the movement and aggregation of organelles, and the transportation of defense compounds, thus serving as an important platform for responding to pathogen infections. Meanwhile, pathogens produce effectors targeting the cytoskeleton to achieve pathogenicity. Recent findings have uncovered several cytoskeleton-associated proteins mediating cytoskeletal remodeling and defense signaling. Furthermore, the reorganization of the actin cytoskeleton is revealed to further feedback-regulate reactive oxygen species (ROS) production and trigger salicylic acid (SA) signaling, suggesting an extremely complex role of the cytoskeleton in plant immunity. Here, we describe recent advances in understanding the host cytoskeleton dynamics upon sensing pathogens and summarize the effectors that target the cytoskeleton. We highlight advances in the regulation of cytoskeletal remodeling associated with the defense response and assess the important function of the rearrangement of the cytoskeleton in the immune response. Finally, we propose suggestions for future research in this area.

Analysis of QTLs and Candidate Genes for Tassel Symptoms in Maize Infected with Sporisorium reilianum

Heat smut is a fungal soil-borne disease caused by Sporisorium reilianum, and affects the development of male and female tassels. Our previous research found that the tassel symptoms in maize infected with Sporisorium reilianum significantly differed in inbred lines with Sipingtou blood, and exhibited stable heredity over time at multiple locations. In this study, cytological analysis demonstrated that the cellular organization structures of three typical inbred lines (Huangzao4, Jing7, and Chang7-2) showed significant discrepancies at the VT stage. QTLs that control the different symptoms of maize tassels infected with Sporisorium reilianum were located in two F₂ populations, which were constructed using three typical inbred lines. The BSA (bulked segregation analysis) method was used to construct mixed gene pools based on typical tassel symptoms. The QTLs of different symptoms of maize tassels infected with Sporisorium reilianum were detected with 869 SSR markers covering the whole maize genome. The mixed gene pools were screened with polymorphic markers between the parents. Additional SSR markers were added near the above marker to detect genotypes in partially single plants in F₂ populations. The QTL controlling tassel symptoms in the Huangzao4 and Jing7 lines was located on the bin 1.06 region, between the markers of umc1590 and bnlg1598, and explained 21.12% of the phenotypic variation with an additive effect of 0.6524. The QTL controlling the tassel symptoms of the Jing7 and Chang7-2 lines was located on the bin 2.07 region, between the markers of umc1042 and bnlg1335, and explained 11.26% phenotypic variation with an additive effect of 0.4355. Two candidate genes (ZmABP2 and Zm00001D006403) were identified by a conjoint analysis of label-free quantification proteome sequencings.

Seaweed-Derived Phenolic Compounds in Growth Promotion and Stress Alleviation in Plants

Abiotic and biotic stress factors negatively influence the growth, yield, and nutritional value of economically important food and feed crops. These climate-change-induced stress factors, together with the ever-growing human population, compromise sustainable food security for all consumers across the world. Agrochemicals are widely used to increase crop yield by improving plant growth and enhancing their tolerance to stress factors; however, there has been a shift towards natural compounds in recent years due to the detrimental effect associated with these agrochemicals on crops and the ecosystem. In view of these, the use of phenolic biostimulants as opposed to artificial fertilizers has gained significant momentum in crop production. Seaweeds are marine organisms and excellent sources of natural phenolic compounds that are useful for downstream agricultural applications such as promoting plant growth and improving resilience against various stress conditions. In this review, we highlight the different phenolic compounds present in seaweed, compare their extraction methods, and describe their downstream applications in agriculture.