Next Article in Journal
A Comprehensive Morphological, Biochemical, and Sensory Study of Traditional and Modern Apple Cultivars
Next Article in Special Issue
Molecular Characterization and Pathogenicity Analysis of Alternaria alternata Associated with Leaf Spot Disease of Toona sinensis in China
Previous Article in Journal
Enhancement of Growth and Quality of Winter Watermelon Using LED Supplementary Lighting
Previous Article in Special Issue
Carrier-Based Application of RsPod1EGY Phage to Effective Control Potato Bacterial Wilt
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Horticulturae
Volume 11
Issue 3
10.3390/horticulturae11030263
horticulturae-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Effects and Inhibition Mechanism of Indole-3-Carboxaldehyde in Controlling Scutellaria baicalensis Root Rot

by
Li Wang
1,
Xin Guo
2 and
Lirong Han
3,*
1
College of YiZhi Agriculture and Forestry, Xian Yang Vocational Technical College, Xianyang 712000, China
2
Shangluo Traditional Chinese Medicine Industry Development Centre, Shangluo 726000, China
3
College of Forestry, Northwest A&F University, Xianyang 712100, China
*
Author to whom correspondence should be addressed.
Horticulturae 2025, 11(3), 263; https://doi.org/10.3390/horticulturae11030263
Submission received: 2 January 2025 / Revised: 30 January 2025 / Accepted: 5 February 2025 / Published: 1 March 2025
(This article belongs to the Special Issue Sustainable Management of Pathogens in Horticultural Crops)
Browse Figures
Review Reports Versions Notes

Abstract

:
Scutellaria baicalensis Gorg is a medicinal herb of significant value in traditional Chinese medicine. Root rot is a major issue in S. baicalensis-producing areas. The aim of this study was to evaluate whether indole-3-carboxaldehyde, a metabolite derived from Purpureocillium lilacinum, has a significant effect on Fusarium solani (one of the main pathogenic fungi causing S. baicalensis root rot), and to clarify its antifungal mechanism. We evaluated the toxicity of indole-3-carboxaldehyde to F. solani using the growth rate assay and found that the EC50 value was 59.563 μg/mL; we also performed additional pot experiments under greenhouse conditions. The effects of indole-3-carboxaldehyde on fungal hyphal morphology and ultrastructure were evaluated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Indole-3-carboxaldehyde was found to induce the disintegration of the mitochondrial double membrane in F. solani, as well as cause cell wall separation. Further probing into the effects of indole-3-carboxaldehyde on mitochondrial aspects was conducted using enzyme activity test kits and real-time quantitative PCR. The findings indicated that indole-3-carboxaldehyde decreases the mitochondrial membrane potential; reduces the activities of SOD, CAT, POD, and GR enzymes; and hampers the growth of F. solani by suppressing the activity of mitochondrial electron transport chain complex I, resulting in H2O2 accumulation. This disruption of the mitochondrial antioxidant pathway impedes the effective clearance of reactive oxygen species (ROS), ultimately leading to the death of F. solani. Future studies of indole-3-carboxaldehyde should focus on its effect on metabolic pathways, which could facilitate the development of innovative pesticides.

1. Introduction

Scutellaria baicalensis Gorg is a medicinal herb of significant value in traditional Chinese medicine. Modern pharmacological research indicates that its primary extracts, baicalin and baicalein, exhibit a broad spectrum of biological activities [1,2]. The herb is known to clear heat, dry dampness, detoxify diarrhea-causing pathogens, promote hemostasis, provide benefits to the fetus, and to possess antiviral, antitumor, antibacterial, antioxidative, and neuroprotective properties. It is a traditional Chinese herbal medicine with high clinical value [3]. It is widely distributed across temperate zones and tropical mountains in Europe, North America, and East Asia [4] and is utilized as a medicine worldwide. In Nepal, it is traditionally used to treat wounds and insect bites; in Europe and North America, the above-ground parts are utilized as an herbal tea and as a flavoring agent in food [5].
S. baicalensis root rot is a major problem in S. baicalensis-producing areas, and the causative agent is a soil-borne fungus from the genus Fusarium. In Shaanxi, China, Fusarium solani is the primary agent causing S. baicalensis root rot. These pathogens infiltrate the roots and stem bases of seedlings, which leads to root rot [6]. In advanced stages, the stem base may also decay, which results in water-soaked lesions and a weakened structure that causes the plant to wilt and die from insufficient hydration [7]. Infected seedlings may abruptly collapse and suddenly die; if the seedling tissues have begun to lignify, this might result in above-ground symptoms such as chlorosis, stunted growth, and terminal wilting, ultimately resulting in plant mortality. Fluctuations in weather conditions between sunny and rainy periods, high temperatures coupled with humidity, suboptimal plant growth, high activity of soil-dwelling pests, compacted soil, and poor drainage can all exacerbate this disease [8,9].
Microorganisms are highly diverse and capable of metabolizing and synthesizing various natural compounds, including alkaloids, antibiotics, and cytotoxins. Some of these compounds have unique molecular scaffolds and specific functional groups [10]. The pursuit of antimicrobial metabolites has been fueled by their potential applications in the development of new fungicides. The original strain of P. lilacinum was first isolated from the egg masses of the root-knot nematode in Peru and is now distributed worldwide. It can effectively control plant pathogenic nematodes and is also effective for the control of plant pathogens. It can produce auxin-like substances to promote plant growth and mediate the degradation of insoluble phosphate pesticides [11,12,13]. Natural products such as lead compounds can be used to develop new pesticides; P. lilacinum and its metabolites have received widespread research attention. These metabolites inhibit the development and growth of nematode eggs and second-stage juveniles, which promotes the control of nematodes. Tadashi [14] isolated a new type of antibiotic, leucinostatins, from the metabolites of P. lilacinum. This antibiotic is a non-ribosomal peptide compound with toxic activity against various Gram-positive bacteria and fungi; it also inhibits the growth of tumor cells. Cui [15] studied the metabolites of the deep-sea-derived P. lilacinum ZBY-1 and isolated 9(11)-dehydrogenated ergosterol peroxide, ergosterol peroxide, 5α,6α-epoxy-3β-hydroxyergosta-22-ene-7-one, cerebroside A, cerebroside B, cerebroside C, and cerebroside D. Preliminary in vitro anti-tumor activity tests were conducted on these seven compounds, and two of these compounds had strong inhibitory effects on four types of cancer cells. New pesticides can be developed via research and the utilization of natural products. The molecular targets of structurally novel natural products should also be identified [16]. An increasing number of studies of P. lilacinum and its metabolites will aid the molecular design of new pesticides.
The breeding of resistant cultivars may be the optimal strategy for managing this disease; however, chemical control methods have become the most reliable and cost-effective approach for decreasing disease prevalence [17]. The fungicides containing benzyl compounds and oxazole are the main bactericidal agents of S. baicalensis root rot [18]. Tebuconazole, diniconazole, carbendazim, and propiconazole are also potentially useful fungicides. However, resistance to these fungicide classes has been extensively documented in numerous other plant pathogens. Given that S. baicalensis is used as a medicinal herb or food ingredient, pesticide use and the associated residues are of concern. Consequently, recent research has focused on the development of alternative strategies for combating plant fungal diseases. The development and application of microbial agents represent one such strategy [19,20].
Here, we extracted and identified metabolites from Purpureocillium lilacinum H1463. We found that indole-3-carboxaldehyde shows high activity against tobacco mosaic virus (TMV) [21]. Subsequent antibacterial spectrum screening demonstrated that indole-3-carboxaldehyde is effective against S. baicalensis root rot. Here, we characterized its inhibitory effects on S. baicalensis root rot and evaluated the effects of indole-3-carboxaldehyde on fungal hyphal morphology and ultrastructure through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as mitochondrial membrane potential and enzyme activity. The antifungal mechanism was preliminarily elucidated, which will aid the future development of fungicides.

2. Materials and Methods

2.1. Fungicides, Media, and Strains

In preliminary experiments, indole-3-carboxaldehyde was isolated, purified, and subsequently dissolved in 10 mL of methanol to create a stock solution at a concentration of 100 mg/mL [21]. Carbendazim (98% purity), supplied by the Shenyang Research Institute of Chemical Industry (Shenyang, China), was also prepared as a stock solution in 0.1 mol/L hydrochloric acid (HCl, Shenyang Research Institute of Chemical Industry, Shenyang, China) and stored at 4 °C in the dark. A nutrient-rich medium, potato dextrose agar (PDA), was provided as per standard microbiological practices [22]. Fusarium solani, obtained from Shaanxi Province, China, was provided by the Laboratory of Tree Pathology at Northwest A&F University and was maintained on PDA slants at 4 °C.

2.2. Sensitivity to Indole-3-Carboxaldehyde

To assess the sensitivity of mycelial growth to indole-3-carboxaldehyde, we determined EC50 values using F. solani. PDA plates were supplemented with varying concentrations of indole-3-carboxaldehyde, ranging from 0 to 100 μg/mL, at increments of 6.25, 12.5, 25, 50, and 100 μg/m [21]. Inverted mycelial plugs, measuring 5 mm in diameter, were excised from the margins of 3-day-old colonies and subsequently transferred to the center of the treated PDA plates. Following a 7-day incubation period in a growth chamber maintained at 25 °C, the diameters of the colonies were determined by averaging measurements taken in two perpendicular directions. The EC50 values were computed by plotting the percentage growth inhibition against the logarithmic fungicide concentrations [23]. Each strain was tested on three separate PDA plates, and the entire experiment was replicated three times for robustness.

2.3. Efficacy of Indole-3-Carboxaldehyde Against F. solani

The efficacy of indole-3-carboxaldehyde against F. solani was assessed in pot experiments. In accord with the previous in vitro results, appropriate concentrations and composites confirmed in the greenhouse were used. Plastic pots (25 cm diameter) loaded with steam-disinfected soil were inoculated independently with the fungal inoculum at a rate of 0.4% w/w; they were then mixed thoroughly and consistently watered with tap water until saturated. Control pots filled with steam-decontaminated soil were only provided with water. Seedlings were surface-sterilized using sodium hypochlorite (1%), washed with sterile water, and then dried on filter paper. Three surface-sterilized seedlings were spread in separate pots. The drenching method was used, along with a blank control group and an experimental group; each group contained five plants. Carbendazim was used as a positive control, and water was used as a negative control. Twenty mL of a suspension containing 106 spores/mL of F. solani was inoculated in the rhizosphere of S. baicalensis Gorg. The pots were placed in a constant temperature incubator at 25 °C to culture for 24 h, which allowed the pathogen to grow and reproduce in a suitable environment. Three replications of each treatment group were performed. After 15 days, the incidence of root rot in S. baicalensis Gorg plants was determined.

2.4. Disease Assessments

Wilt severity was estimated at 15 days after replanting (i.e., when the negative control shows obvious yellowing of leaves and wilting of plants), using a rating scale of 0–5 based on the degree of leaf yellowing, viz., (0 = healthy, 1 = one leaf yellowing, 2 = more than one leaf yellowing, 3 = one wilted leaf, 4 = more than one leaf faded, and 5 = plant is dead) [24]. The disease severity index (DSI) described by Liu et al. [25] was determined from this equation: DSI = Σd/(dmax × n) × 100, where d is the disease rating of each plant, dmax is the maximum disease rating, and n is the whole number of plants/samples studied in each replicate.

2.5. Effect of Indole-3-Carboxaldehyde on Fungal Mycelia

Mycelial discs (5 mm in diameter) were excised from the periphery of vigorously proliferating F. solani colonies and subsequently transferred onto potato dextrose agar (PDA) plates supplemented with indole-3-carboxaldehyde at their respective EC50 concentrations. Untreated PDA plates served as the control group. Following a 72 h incubation period at 25 °C within a growth chamber, the periphery of the resulting colonies (10 mm × 10 mm) was transferred onto glass slides for examination. The morphology of the mycelial surface was scrutinized using a scanning electron microscope (SEM; JEOL Scanning Electron Microscope JSM-6360LV, Japan) and a transmission electron microscope (TEM; HITACHI Transmission Electron Microscope HT7700, Japan), as previously described by Dong [26] and Zuppini [27].

2.6. Mitochondrial Membrane Potential Detection

Following treatment with EC50 of F. solani, the mycelia were reconstituted in JC-1 staining buffer, as described by Tonshin et al. [28]. Subsequently, 0.5 mL of JC-1 staining solution was introduced, and the mixture was gently inverted to ensure homogeneity. The sample was then subjected to incubation at an ambient temperature for 20 min, followed by two rounds of washing with JC-1 staining buffer. An appropriate volume of JC-1 staining buffer was subsequently used to resuspend the mycelia, which were then examined under a fluorescence microscope. The emission wavelengths monitored were 535 nm (JC-1 monomer) and 595 nm (JC-1 polymer). The mitochondrial membrane potential was assessed by the relative fluorescence intensity ratio of JC-1 polymer as compared to the JC-1 monomer.

2.7. Induction of Intracellular ROS in F. solani Cells

The generation of intracellular H2O2 was quantified using 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) as a fluorescent probe, as previously described by Rosa et al. [29] and Wang [30]. The mycelial samples were incubated with DCFH-DA at a concentration of 0.5 μM and subsequently agitated gently on a shaker for 30 min at 25 °C in a dark environment. Following incubation, the mycelial samples were subjected to three rounds of washing with phosphate-buffered saline (PBS). Intracellular fluorescence was then visualized using fluorescence microscopy, with excitation and emission wavelengths set at 495 nm and 515 nm, respectively.

2.8. Extraction of Mitochondria from F. solani

F. solani mycelium was homogenized in an extraction buffer consisting of 0.4 M mannitol, 1 mM EGTA, 10 mM Tris-HCl at pH 7.4, 0.1% (w/v) bovine serum albumin, and 1% (w/v) PVP-40. Following homogenization, the mixture was subjected to centrifugation at 2500× g for 10 min, and the resultant pellet was removed. The supernatant was then subjected to a second centrifugation at 18,000× g for 12 min, after which the pellet was again discarded. The remaining supernatant was reconstituted in mannitol buffer (0.4 M mannitol, 10 mM Tris-HCl at pH 7.4, and 1 mM EGTA) to yield a crude mitochondrial extract with a protein concentration of 10 mg/mL, as per the method described by Futaki et al. [31]. The protein content was quantified using the Bradford assay [32].

2.9. Effects on the Antioxidase System in Mitochondria

The activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and glutathione reductase (GR) in the mitochondria were measured, as described by Sun et al. [33].

2.10. Effect on Mitochondrial Electron Transport Chain Complex I

Utilizing a refined version of the C503041 Protein Assay Kit and the Electron Transport Chain Complex I Assay Kit A089-1 from Nanjing Jiancheng Bioengineering Institute, Nanjing, China, we successfully extracted and quantified the activity of mitochondrial electron transport chain complex I [34].

2.11. Total RNA Extraction and Quantitative RT-PCR

Total RNA was isolated from the PDA plate (cultured for 72 h) using TRIzol® Reagent (Invitrogen, Carlsbad, CA, USA), and subsequent cDNA synthesis was conducted with 1 μL of the isolated RNA. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was executed on the PTC-200 Real-Time PCR system, employing TB Green™ Premix (Takara, Tokyo, Japan). Gene-specific primers, listed in Supplementary Table S1, were synthesized at a concentration of 25 μM. The GAPDH gene served as an internal control. Relative quantification of the amplification products was determined via the 2−ΔΔCT method, as described by Livak and Schmittgen [35]. Each experiment was conducted in triplicate, and five technical replicates per experiment were performed to ensure statistical robustness.

2.12. Statistical Analysis

The dataset was analyzed using SPSS version 22 (SPSS, Inc., Chicago, IL, USA). Univariate techniques were used to compute the mean values for each treatment group. To ascertain the presence of statistically significant differences between treatments, the Tukey post hoc test was conducted at a significance level of p = 0.05.

3. Results

3.1. Indole-3-Carboxaldehyde Inhibits F. solani

The mycelial diameter was inversely related to indole-3-carboxaldehyde concentrations, and the degree of inhibition was directly proportional to indole-3-carboxaldehyde concentrations. The EC50 was 59.56 μg/mL, the correlation coefficient was 0.9673, and the regression equation was Y = 2.00x − 3.55 (Table 1).

3.2. Performance of S. baicalensis Gorg Under Greenhouse Conditions

Table 2 and Supplementary Figure S1 show substantial fluctuations in the disease metrics for S. baicalensis Gorg, following exposure to indole-3-carboxaldehyde treatments, after 15 days. The disease index, disease incidence, and pathogen control efficacy were 36.45%, 41.00%, and 57.91% lower, respectively, in seedlings subjected to indole-3-carboxaldehyde than in untreated, infected controls. The performance of indole-3-carboxaldehyde was marginally less robust than that of carbendazim.

3.3. SEM and TEM Observations

Scanning electron microscopy (SEM) analysis showed that the indole-3-carboxaldehyde-treated mycelia at a concentration of 59.56 μg/mL had excessive branches and were curled, while the untreated mycelia displayed direct and symmetrical growth patterns (Figure 1A,B). Transmission electron microscopy (TEM) observations revealed that treatment with 59.56 μg/mL of indole-3-carboxaldehyde led to notable alterations in the cell wall, which appeared thinner and aberrant. The septa were distorted, the cytoplasm was disorganized, the mitochondrial bilayer membrane had disintegrated, and the cells were plasmolyzed (Figure 1D). In contrast, untreated hyphal cells had clearly defined mitochondria, exhibited normal organelle morphology, had balanced vacuolar structures, and had a uniform cytoplasmic distribution (Figure 1C).

3.4. Mitochondrial Measurements

The JC-1 probe, which is specifically used to determine the mitochondrial membrane potential, was used to monitor alterations in this parameter (Figure 2). A substantial reduction in mitochondrial membrane potential was observed following exposure to 59.56 μg/mL of indole-3-carboxaldehyde. In the control group, the mitochondria predominantly exhibited a red fluorescence, suggesting that the membrane potential was healthy. Conversely, mycelia treated with indole-3-carboxaldehyde predominantly showed a green fluorescence (Figure 2 and Figure 4A), indicating that indole-3-carboxaldehyde induced a decline in the mitochondrial membrane potential.

3.5. H2O2 Accumulation

In our study, a DCFH-DA fluorescence assay was used to monitor alterations in reactive oxygen species (ROS) levels within anthrax bacteria following exposure to indole-3-carboxaldehyde. A pronounced increase in fluorescence intensity was observed under indole-3-carboxaldehyde treatment, and green fluorescence was distributed throughout most hyphal structures, as shown in Figure 3 and Figure 4B.

3.6. Effect of Indole-3-Carboxaldehyde on the Activities of Enzymes in Mitochondria

The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR) within the mitochondria play key roles in the defense mechanisms of plants against pathogens and in the generation of oxygen. We assessed the enzymatic activities of SOD, CAT, POD, and GR in F. solani mycelia that had been treated with indole-3-carboxaldehyde. Our findings indicate that indole-3-carboxaldehyde led to a reduction in the activities of SOD, CAT, POD, and GR enzymes (Figure 4C–F).
Horticulturae 11 00263 g004
Figure 4. Effect of indole-3-carboxaldehyde on activities in mitochondria. The H2O2 accumulation (A), mitochondrial membrane potential (ΔΨm, B), catalase (CAT, C), superoxide dismutase (SOD, D), peroxidase (POD, E), and glutathione reductase (GR, F) activities of mycelia of F. solani treated with indole-3-carboxaldehyde (59.56 μg/mL) were determined. Asterisk indicates significant (p < 0.05) differences.
Figure 4. Effect of indole-3-carboxaldehyde on activities in mitochondria. The H2O2 accumulation (A), mitochondrial membrane potential (ΔΨm, B), catalase (CAT, C), superoxide dismutase (SOD, D), peroxidase (POD, E), and glutathione reductase (GR, F) activities of mycelia of F. solani treated with indole-3-carboxaldehyde (59.56 μg/mL) were determined. Asterisk indicates significant (p < 0.05) differences.
Horticulturae 11 00263 g004

3.7. Effect of Indole-3-Carboxaldehyde on Electron Transport Chain Complex I (NADH- Coenzyme Q Reductase) Activity in F. solani

The activity of electron transport chain complex I was reduced; the activity of electron transport chain complex I was three times that of the control, indicating that indole-3-carboxaldehyde can control the growth of F. solani by inhibiting the activity of mitochondria electron transport chain complex I (Figure 5A).

3.8. Effect of Indole-3-Carboxaldehyde on Electron Transport Chain Complex I-Related Gene Expression

To verify that indole-3-carboxaldehyde inhibits electron transport chain complex I, NADH ubiquinone oxidoreductase subunit (nad1-6) transcripts were detected using RT-qPCR. After treatment with 59.56 μg/mL indole-3-carboxaldehyde, the expression of NAD1, NAD2, NAD3, and NAD6 significantly decreased; their mRNA reached their lowest expression levels, which were 0.65, 0.35, 0.36, and 0.12 times of the control, suggesting that indole-3-carboxaldehyde apparently inhibited the electron transport chain complex I in F. solani (Figure 5B).

4. Discussion

Indole-derived secondary metabolites are a large group of compounds that are diverse in structure and show various biological activities; they are potentially useful for the development of new pesticides. Indole–quinoline alkaloids possess high antibacterial and antitumor activities. Neosurugatoxin, for instance, has the strongest virulence against Rhizoctonia solani. It acts on the Fe-S protein subunit of mitochondrial complex III, which significantly inhibits its enzymatic activity, disrupts the electron transport chain and energy metabolism, and causes hyphal death. Additionally, the fungicidal activity of neosurugatoxin may be related to the inhibition of nuclear function [36,37]. Recent studies have identified the novel rhizosphere-promoting bacterial strain Streptomyces lasalocidi JCM 3373, which secretes indole-3-carboxaldehyde to improve root structure and alleviate salt stress in soybeans [38]. Previous studies in our laboratory have found that indole-3-carboxaldehyde significantly protects tobacco from TMV infection and can trigger systemic immune responses in plants [13]. We found that indole-3-carboxaldehyde can suppress F. solani and analyzed its antibacterial mechanism; this will aid the development and application of fungicides.
Indole-3-carboxaldehyde induced the disintegration of the mitochondrial bilayer membrane, and the cells exhibited plasmolysis. These effects indicate that the action sites of indole-3-carboxaldehyde against F. solani are highly vulnerable to attack. Plodpai et al. [39] used Desmos chinensis extracts to control rice sheath blight. As consequences of the benzoate esters and benzoic acid derivatives, this treatment resulted in cytoplasmic vacuolation, the folding of some sites of the membrane, the breakdown and plasmolysis of the cell wall, and the disorganization and depletion of the cytoplasm and membranous organelles, resulting in cell death. In the presence of the culture filtrate of Streptomyces philanthi RM-1-138, the cell wall of Rhizoctonia solani became seriously distorted, the cytoplasm erupted, the septum became disordered, and almost no mitochondria could be identified [40].
Mitochondria are important organelles that produce ATP. Previous research has focused on pesticides with effects on the mitochondrial electron transport chain. Complexes I to IV, ubiquinones, cytochromes, and iron–sulfur proteins are components of electron transport chains [41]. Electron transport chain complex I is necessary for the transport of electrons during reactions, which directly affects the continued transport of electrons. High activity of complex I maintains normal electron transport, but low activity of complex I terminates or weakens electron transport, which limits respiration. Electron transport chain complex I is usually treated as an important target of pesticides. Our research showed that indole-3-carboxaldehyde can lead to declines in mitochondrial membrane potential; reduce the activities of the SOD, CAT, and GR enzymes; control the growth of F. solani by inhibiting the activity of mitochondria electron transport chain complex I and the expression of related genes; and promote H2O2 accumulation. The mitochondria are therefore a target of indole-3-carboxaldehyde. Our findings suggest that indole-3-carboxaldehyde disrupts the mitochondrial antioxidant pathway in the target bacteria, which impedes the timely elimination of ROS. This results in ROS accumulation, which in turn alters the mitochondrial membrane potential and leads to the death of F. solani. Further studies are required to explore whether other complexes also constitute targets. Additionally, as no studies to date have systematically analyzed or identified genes associated with the mitochondria of F. solani, because of time constraints, we were unable to analyze changes in the expression of genes encoding components of the mitochondrial electron transport chain complexes.

5. Conclusions

Indole-3-carboxaldehyde was procured from the metabolites of P. lilacinum. Nevertheless, the impact of this metabolite on crop fungal diseases has not been extensively explored. However, it has been demonstrated to be efficacious in the management of plant nematodes [42]. Characterized by its simple structure, facile synthesis, and environmental friendliness, Indole-3-carboxaldehyde has potential relative to the molecular design and synthesis of fungicides. Further studies will be needed to analyze the effects of indole-3-carboxaldehyde on the expression of genes encoding key regulators of the growth, development, and pathogenesis of F.solani.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/horticulturae11030263/s1: Supplementary Figure S1, Scutellaria baicalensis Gorg growth characteristics after application with indole-3-carboxaldehyde’ treatments under greenhouse conditions. Supplementary Table S1, Primers used for PCR amplification.

Author Contributions

L.W. and L.H. conceived and designed the experiments. L.W., X.G. and L.H. conducted the experiments, performed the analyses, and collected the data. L.W. and X.G. prepared a first draft of the manuscript, and L.W., X.G. and L.H. read and edited the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

Doctoral Startup Fund Project of Xian yang Vocational Technical College (2022BK03).

Data Availability Statement

Data is contained within the article or Supplementary Materials.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Shen, J.; Li, p.; Liu, S.S.; Liu, Q.; Li, Y.; Sun, Y.H.; He, C.N.; Xiao, P.G. Traditional uses, ten-years research progress on phytochemistry and pharmacology, and clinical studies of the genus Scutellaria. J. Ethnopharmacol. 2021, 265, 113–198. [Google Scholar] [CrossRef] [PubMed]
  2. Song, J.Y.; Long, L.; Xie, L.L.; Zhang, Q.X.; Xie, H.J.; Chen, M.; Deng, X.F. Applications, phytochemistry, pharmacological effects, pharmacokinetics, toxicity of Scutellaria baicalensis Georgi. and its probably potential therapeutic effects on COVID-19: A review. Chin. Med. 2020, 15, 102. [Google Scholar] [CrossRef] [PubMed]
  3. Wang, Z.L.; Wang, S.; Kuang, Y.; Hu, Z.M.; Qiao, X.; Ye, M.A. comprehensive review on phytochemistry, pharmacology, and flavonoid biosynthesis of Scutellaria baicalensis. Pharm. Biol. 2018, 56, 465–484. [Google Scholar] [CrossRef] [PubMed]
  4. Bruno, M.; Piozzi, F.; Maggie, A.M.; Simmonds, M.S.J. Antifeedantactivity of neoclerodane diverse oils from two Sicilian species of Scutellaria. Biochem. Syst. Ecol. 2002, 30, 793–799. [Google Scholar] [CrossRef]
  5. Zhao, T.; Tang, H.; Xie, L.; Zheng, Y.; Ma, Z.; Sun, Q.; Li, X. Scutellaria baicalensis Georgi. (Lamiaceae): A review of its traditional uses, botany, phytochemistry, pharmacology and toxicology. J. Pharm. Pharmacol. 2019, 71, 1353–1369. [Google Scholar] [CrossRef]
  6. Chang, J.; Jing, J.X.; Zhang, H.K.; Yang, M.N.; Wang, Z.Z. Identification on the Pathogen of Stem Wilt of Scutellaria baicalensis in Shaanxi. J. Northwest F. Univ. 2006, 3, 81–82. [Google Scholar]
  7. Ghoniem, A.; Rashad, E.M.; El-Khateeb, A.; Saber, W. Technology Bacteriological therapeutic-based strategy for management of fusarium wilt disease in tomato plants. Mindanao J. Sci. Technol. 2020, 18, 174–193. [Google Scholar] [CrossRef]
  8. Jones, J.B.; Zitter, T.A.; Momol, T.M.; Miller, S.A. Compendium of Tomato Diseases and Pests, Second Edition. Am. Phytopathol. Society 2016, 2, 120–127. [Google Scholar]
  9. Zhang, H.L.; Ge, L.L.; Chen, K.P.; Zhao, L.N.; Zhang, X.Y. Enhanced biocontrol activity of Rhodotorula mucilaginosa cultured in media containing chitosan against postharvest diseases in strawberries: Possible mechanisms underlying the effect. J. Agric. Food Chem. 2014, 62, 4214–4224. [Google Scholar] [CrossRef]
  10. Berdy, J. Recent developments of antibiotic research and classification of antibiotics according to chemical structure. Adv. Appl. Microbiol. 1974, 18, 309–406. [Google Scholar]
  11. Jennifer, L.; Jos, H.; Tineke, D.; Hong, S.B.; Borman, A.M.; Hywel-Jones, N.L.; Samson, R.A. Purpureocillium, a new genus for the medically important paecilomyces lilacinus. FEMS Microbiol. Letters 2011, 321, 141–149. [Google Scholar]
  12. Aguilar, C.; Pujol, I.; Sala, J.; Guarro, J. Antifungal susceptibilities of Paecilomyces species. Antimicrob. Agents Chemotherapy. 1998, 42, 1601–1604. [Google Scholar] [CrossRef] [PubMed]
  13. Wang, G.; Liu, Z.G.; Lin, R.M.; Li, E.F.; Mao, Z.C.; Ling, J.; Yang, Y.H.; Yin, W.B.; Xie, B.Y. Biosynthesis of antibiotic leucinostatins in bio-controlfungus Purpureocillium lilacinum and their inhibition on phytophthora revealed by genome mining. PLoS Pathog. 2016, 12, 1005685. [Google Scholar] [CrossRef]
  14. Tadashi, A.; Yuzuru, M.; Kazutaka, F.; Takehiko, U. A new antibiotic, leucinostatin, derived from Penicillium lilacinum. J. Antibiotics. 1973, 26, 157–161. [Google Scholar]
  15. Cui, X.; Li, C.W.; Wu, C.J.; Hua, W.; Gu, Q.Q. Metabolites of paecilomyces lilacinus zby-1 from deep-sea water and their antitumor activity. J. Int. Pharm. Res. 2013, 40, 177–186. [Google Scholar]
  16. Jung, H.J.; Kwon, H.J. Target deconvolution of bioactive small molecules: The heart of chemical biology and drug discovery. Arch. Pharm. Res. 2015, 38, 1627–1641. [Google Scholar] [CrossRef]
  17. Wang, Y.; Wang, M.; Zhou, M.; Zhang, X.; Feng, J. Baseline sensitivity and action mechanism of propamidine against alternaria brassicicola, the causal agent of dark leaf spot on cabbage. Plant Disease. 2019, 104, 204–210. [Google Scholar] [CrossRef]
  18. Zene, A.S.; Tian, Y.Q.; Zhang, J.Q. The Effect of Bacillus Bacteria on Tomato Plants and Fruits. Int. J. Agric. Innov. 2021, 9, 271–280. [Google Scholar]
  19. Sun, Y.; Wang, Y.; Xie, Z.Y.; Guo, E.H.; Han, L.R.; Zhang, X.; Feng, J.T. Activity and biochemical characteristics of plant extract cuminic acid against Sclerotinia sclerotiorum. Crop Prot. 2017, 101, 76–83. [Google Scholar] [CrossRef]
  20. Wang, L.Y.; Ren, X.Y.; Guo, W.H.; Wang, D.L.; Han, L.R.; Feng, J.T. Oxidative Stress and Apoptosis of Gaeumannomyces graminis (Get) Induced by Carabrone. J. Agric. Food Chem. 2019, 67, 10448–10457. [Google Scholar] [CrossRef]
  21. Sun, Y.B.; Wu, H.; Zhou, W.N.; Yuan, Z.C.; Hao, J.J.; Liu, X.L.; Han, L.R. Effects of indole derivatives from purpureocillium lilacinum in controlling tobacco mosaic virus. Pestic. Biochem. Physiol. 2022, 183, 105077. [Google Scholar] [CrossRef] [PubMed]
  22. Hou, Y.P.; Mao, X.W.; Lin, S.P.; Song, X.S.; Duan, Y.B.; Wang, J.X.; Zhou, M.G. Activity of a novel succinate dehydrogenase inhibitor fungicide pyraziflumid 416 against Sclerotinia sclerotiorum. Pestic. Biochem. Physiol. 2018, 145, 22–28. [Google Scholar] [CrossRef] [PubMed]
  23. Duan, Y.B.; Ge, C.Y.; Liu, S.M.; Chen, C.J.; Zhou, M.G. Effect of phenylpyrrole 396 fungicide fludioxonil on morphological and physiological characteristics of Sclerotinia 397 sclerotiorum. Pestic. Biochem. Physiol. 2013, 106, 61–67. [Google Scholar] [CrossRef]
  24. Martijn, R. Small proteins of plant-pathogenic fungi secreted during host colonization. Fems. Microbiol. Lett. 2010, 253, 19–27. [Google Scholar]
  25. Liu, J.; Kloepper, J.W.; Tuzun, S. Induction of systemic resistance in cucumber against Fusarium wilt by plant growth-promoting rhizobacteria. Am. Phytopathol. Society 1995, 85, 695–698. [Google Scholar] [CrossRef]
  26. Dong, Z.J.; Chu, J.Y.; Xie, S. The cryogenic scanning electron microscope of fungi. Microbiology 1987, 1, 41–43. [Google Scholar]
  27. Zuppini, A.; Baldan, B.; Millioni, R.; Favaron, F.; Mariani, N.P. Chitosan induces Ca2+-ediated programmed cell death in soybean cells. New Phytol. 2003, 161, 557–568. [Google Scholar] [CrossRef]
  28. Tonshin, A.A.; Saprunova, V.B.; Solodovnikova, I.M.; Bakeeva, L.E.; Yaguzhinsky, L.S. Functional activity and ultrastructure of mitochondria isolated from myocardial apoptotic tissue. Biochemistry 2003, 68, 875–881. [Google Scholar]
  29. Rosa, A.V.; Maria, C.P.; Daniela, V.; Salvatore, P.; Ersilia, M.; Laura, D.G. Production of reactive oxygen species, alteration of cytosolic ascorbate peroxidase, and impairment of mitochondrial metabolism are early events in heat shock-induced programmed cell death in tobacco bright-yellow 2 cells. Plant Physiol. 2004, 34, 1100–1112. [Google Scholar]
  30. Wang, Y.; Sun, Y.; Wang, J.L.; Zhou, M.X.; Wang, M.M.; Feng, J.T. Antifungal activity and action mechanism of the natural product cinnamic acid against Sclerotinia sclerotiorum. Plant Disease 2019, 103, 944–950. [Google Scholar] [CrossRef]
  31. Futaki, S.; Suzuki, T.; Ohashi, W.; Yagami, T.; Tanaka, S.; Ueda, K. Argininerich peptides: An abundant source of membrane-permeable peptides having potential as carriers for intracellular protein delivery. J. Biol. Chem. 2001, 276, 5836–5840. [Google Scholar] [CrossRef] [PubMed]
  32. Fan, H.; Song, B.; Bhadury, P.S.; Jin, L.; Yang, S. Antiviral activity and mechanism of action of novel thiourea containing chiral phosphonate on tobacco mosaic virus. Int. J. Mol. Sci. 2011, 12, 4522–4535. [Google Scholar] [CrossRef] [PubMed]
  33. Sun, Y.B.; Tian, X.R.; Wu, H.; Hao, X.C.; Gao, B.W.; Zhang, H.Y.; Fang, J.T.; Han, L.R. H2O2 signaling modulates Glycoprotein-1 induced programmed cell death in tobacco suspension cells. Pestic. Biochem. Physiol. 2020, 171, 104697. [Google Scholar] [CrossRef] [PubMed]
  34. Xiang, Y.Q.; Zhang, Y.; Wang, C.; Liu, S.Q.; Liao, X.L. Effects and inhibition mechanism of phenazine-1-carboximade on the mycelial morphology and ultrastructure of rhizoctonia solani. Pestic. Biochem. Physiol. 2018, 147, 32–39. [Google Scholar] [CrossRef]
  35. Livak, K.J.; Schmittgen, T.D. Analysis of relative gene expression data using realtime quantitative PCR and the 2(−Delta Delta C(T)) method. Methods 2001, 25, 402–408. [Google Scholar] [CrossRef]
  36. Shang, X.F.; Morris-Natschke, S.L.; Yang, G.Z.; Liu, Y.Q.; Guo, X.; Xu, X.S.; Goto, M.; Li, J.C.; Zhang, J.Y.; Lee, K.H. Biologically active quinoline and quinazoline alkaloids part I. Med. Res. Rev. 2018, 38, 775–828. [Google Scholar] [CrossRef]
  37. Shang, X.F.; Morris-Natschke, S.L.; Yang, G.Z.; Liu, Y.Q.; Guo, X.; Xu, X.S.; Goto, M.; Li, J.C.; Zhang, J.Y.; Lee, K.H. Biologically active quinoline and quinazoline alkaloids part II. Med. Res. Rev. 2018, 38, 1614–1660. [Google Scholar] [CrossRef]
  38. Lu, L.; Liu, N.; Fan, Z.H.; Liu, M.H.; Zhang, X.X.; Tian, J.; Yu, Y.J.; Lin, H.H.; Huang, Y.; Kong, Z.S. A novel PGPR strain, Streptomyces lasalocidi JCM 3373, alleviates salt stress and shapes root architecture in soybean by secreting indole-3-carboxaldehyde. Plant Cell Environ. 2024, 47, 1941–1956. [Google Scholar] [CrossRef]
  39. Plodpai, S.; Chuenchitt, V.; Petcharat, S.; Chakthong, S.P. Voravuthikunchai, AntiRhizoctonia solani activity by Desmos chinensis extracts and its mechanism of action. Crop. Prot. 2013, 43, 65–71. [Google Scholar] [CrossRef]
  40. Boukaew, P.; Prasertsan, P. Suppression of rice sheath blight disease using a heat stable culture filtrate from Streptomyces philanthi RM-1-138. Crop. Prot 2014, 61, 1–10. [Google Scholar] [CrossRef]
  41. Wang, M.; Lan, W.; Han, L.; Zhang, X.; Feng, J. The effect of carabrone on mitochondrial respiratory chain complexes in Gaeumannomyces graminis. J. Appl. Microbiol. 2017, 123, 1100–1110. [Google Scholar] [CrossRef] [PubMed]
  42. Loureiro, E.; Neto, J.; Pessoa, L.; Dias, P.; Yokota, L. Efeito de produtos fitossanitarios’ químicos sobre os fungos Trichoderma harzianum (Ecotrich) e Purpureocillium lilacinum (Nemat). Res. Soc. Dev. 2020, 9, 141963506. [Google Scholar] [CrossRef]
Horticulturae 11 00263 g001
Figure 1. SEM images and TEM images of the morphology of mycelia exposed to indole-3-carboxaldehyde. (A,C) show healthy mycelia in control Petri plates. (B,D) show the effects of indole-3-carboxaldehyde on hyphal morphology at 59.56 μg/m. The untreated mycelia displayed direct and symmetrical growth patterns (A); mycelia treated with indole-3-carboxaldehyde had excessive branches and were curled (B). The mitochondria were clearly visible, the morphology of the organelles was normal, the vacuoles were balanced, and the cytoplasm was uniform (C). The cytoplasm was mixed, the mitochondria were absent, the vacuoles were smaller, and the cells were plasmolyzed (D). MI: mitochondria; VA: vacuole; PM: plasma membrane; CW: cell wall. Scale bars = 1 μm.
Figure 1. SEM images and TEM images of the morphology of mycelia exposed to indole-3-carboxaldehyde. (A,C) show healthy mycelia in control Petri plates. (B,D) show the effects of indole-3-carboxaldehyde on hyphal morphology at 59.56 μg/m. The untreated mycelia displayed direct and symmetrical growth patterns (A); mycelia treated with indole-3-carboxaldehyde had excessive branches and were curled (B). The mitochondria were clearly visible, the morphology of the organelles was normal, the vacuoles were balanced, and the cytoplasm was uniform (C). The cytoplasm was mixed, the mitochondria were absent, the vacuoles were smaller, and the cells were plasmolyzed (D). MI: mitochondria; VA: vacuole; PM: plasma membrane; CW: cell wall. Scale bars = 1 μm.
Horticulturae 11 00263 g001
Horticulturae 11 00263 g002
Figure 2. Mycelia treated with 59.56 μg/mL indole-3-carboxaldehyde and untreated control mycelia were used to determine the mitochondrial membrane potential (ΔΨm).
Figure 2. Mycelia treated with 59.56 μg/mL indole-3-carboxaldehyde and untreated control mycelia were used to determine the mitochondrial membrane potential (ΔΨm).
Horticulturae 11 00263 g002
Horticulturae 11 00263 g003
Figure 3. Mycelia treated with indole-3-carboxaldehyde (59.56 μg/mL), which induces H2O2 accumulation, and untreated mycelia.
Figure 3. Mycelia treated with indole-3-carboxaldehyde (59.56 μg/mL), which induces H2O2 accumulation, and untreated mycelia.
Horticulturae 11 00263 g003
Horticulturae 11 00263 g005
Figure 5. Effect of indole-3-carboxaldehyde on electron transport chain complex I (NADH-coenzyme Q reductase) activity (A) and the expression of related genes (B). Experiments were repeated two times, and the same results were obtained in each replication. The asterisk indicates significant differences relative to the control according to one-way ANOVA at p < 0.01.
Figure 5. Effect of indole-3-carboxaldehyde on electron transport chain complex I (NADH-coenzyme Q reductase) activity (A) and the expression of related genes (B). Experiments were repeated two times, and the same results were obtained in each replication. The asterisk indicates significant differences relative to the control according to one-way ANOVA at p < 0.01.
Horticulturae 11 00263 g005
Table 1. Inhibition of indole-3-Carboxaldehyde against F. solani.
Table 1. Inhibition of indole-3-Carboxaldehyde against F. solani.
TreatmentEC50
(μg/mL)		95%
Confidence Limits
(μg/mL)		Regression Equation
(y=)		Correlation Coefficient (R2)
Indole-3-carboxaldehyde59.5643.32–84.562.00x − 3.550.9673
Carbendazim39.8234.91–45.222.36x − 3.780.9842
Table 2. Potted method for the control of Fusarium solani by indole-3-carboxaldehyde.
Table 2. Potted method for the control of Fusarium solani by indole-3-carboxaldehyde.
TreatmentIncidence Rate (%)Disease IndexControl Efficacy (%)
Indole-3-carboxaldehyde41.0036.4557.91
Carbendazim26.6728.0067.67
Water61.2086.60—
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Wang, L.; Guo, X.; Han, L. Effects and Inhibition Mechanism of Indole-3-Carboxaldehyde in Controlling Scutellaria baicalensis Root Rot. Horticulturae 2025, 11, 263. https://doi.org/10.3390/horticulturae11030263

AMA Style

Wang L, Guo X, Han L. Effects and Inhibition Mechanism of Indole-3-Carboxaldehyde in Controlling Scutellaria baicalensis Root Rot. Horticulturae. 2025; 11(3):263. https://doi.org/10.3390/horticulturae11030263

Chicago/Turabian Style

Wang, Li, Xin Guo, and Lirong Han. 2025. "Effects and Inhibition Mechanism of Indole-3-Carboxaldehyde in Controlling Scutellaria baicalensis Root Rot" Horticulturae 11, no. 3: 263. https://doi.org/10.3390/horticulturae11030263

APA Style

Wang, L., Guo, X., & Han, L. (2025). Effects and Inhibition Mechanism of Indole-3-Carboxaldehyde in Controlling Scutellaria baicalensis Root Rot. Horticulturae, 11(3), 263. https://doi.org/10.3390/horticulturae11030263

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop