Verticillium Wilt Of Cotton Research Articles

GhTBL34 Is Associated with Verticillium Wilt Resistance in Cotton.

Verticillium wilt (VW) is a typical fungal disease affecting the yield and quality of cotton. The Trichome Birefringence-Like protein (TBL) is an acetyltransferase involved in the acetylation process of cell wall polysaccharides. Up to now, there are no reports on whether the TBL gene is related to disease resistance in cotton. In this study, we cloned a cotton TBL34 gene located in the confidence interval of a major VW resistance quantitative trait loci and demonstrated its relationship with VW resistance in cotton. Analyzing the sequence variations in resistant and susceptible accessions detected two elite alleles GhTBL34-2 and GhTBL34-3, mainly presented in resistant cotton lines whose disease index was significantly lower than that of susceptible lines carrying the allele GhTBL34-1. Comparing the TBL34 protein sequences showed that two amino acid differences in the TBL (PMR5N) domain changed the susceptible allele GhTBL34-1 into the resistant allele GhTBL34-2 (GhTBL34-3). Expression analysis showed that the TBL34 was obviously up-regulated by infection of Verticillium dahliae and exogenous treatment of ethylene (ET), and salicylic acid (SA) and jasmonate (JA) in cotton. VIGS experiments demonstrated that silencing of TBL34 reduced VW resistance in cotton. We deduced that the TBL34 gene mediating acetylation of cell wall polysaccharides might be involved in the regulation of resistance to VW in cotton.

Diversity and Biocontrol Potential of Culturable Endophytic Fungi in Cotton.

Healthy cotton samples were collected and 93 endophytic fungal strains were isolated: 23 strains from the roots and 70 strains from the stems. Morphological characterization and ITS sequence analysis were used for the identification of these isolates. The results showed that the 93 strains including 20 species were highly diverse in terms of their taxonomy. Simpson’s and Shannon’s diversity indices were 0.915 and 3.848, respectively. Fusarium and Alternaria were the two dominant genera, constituting 19.4% of the total strains. Then, 72 spore-producing strains were tested for the suppression of cotton Verticillium wilt (CVW) caused by Verticillium dahliae in a greenhouse. Five strains exhibited effective suppression of CVW with average efficacy values higher than 50%. One of the effective strains, namely, Fusarium proliferatum 10R-7, was selected for the investigation of the role of fusaric acid, a secondary metabolite of strain 10R-7, in the suppression of V. dahliae and CVW. The results showed that F. proliferatum 10R-7 could produce fusaric acid, and this metabolite exhibited 100% inhibition of mycelial growth of V. dahliae at concentrations higher than 20 μg/ml. However, fusaric acid at 2.5 to 80 μg/ml was not effective in the suppression of CVW, compared with the control treatment with V. dahliae alone. F. proliferatum 10R-7 was labeled with green fluorescent protein (GFP), and the GFP-tagged strain was found to be able to colonize inside the taproots of cotton, suggesting that F. proliferatum 10R-7 is a true endophyte of cotton and endophytic colonization may play a role in the suppression of infection of cotton by V. dahliae.

Green Fluorescent Protein-Tagged Bacillus axarquiensis TUBP1 Reduced Cotton Verticillium Wilt Incidence by Altering Soil Rhizosphere Microbial Communities.

Verticillium wilt is a major disease of cotton that considerably decreases yield and crop quality. Soil microbial communities play an important role in plant health. Therefore, biocontrol bacteria that regulate microbial communities in rhizosphere soil can improve plant resistance to pathogens. Previously, the antagonistic strain Bacillus axarquiensis TUBP1 was screened and found to act against Verticillium dahliae with 43% biocontrol effect in cotton fields. We studied the effect of Bacillus axarquiensis TUBP1 with a green fluorescent protein (GFP) gene marker on the microbial community structure of cotton rhizosphere soil and cotton yield and quality. Cotton Verticillium wilt incidence, soil biochemical properties, and soil bacterial and fungal communities were analyzed. Results showed that bacterial and fungal abundance in cotton rhizosphere soil was temporarily changed after applying B. axarquiensis TUBP-315GFP. However, Bacillus significantly increased, whereas V. dahliae significantly decreased. The incidence of cotton Verticillium wilt after treatment with B. axarquiensis TUBP-315GFP was significantly lower and cotton production increased by 40.6%. Our findings indicated that the application of B. axarquiensis TUBP-315GFP can change microbial community structure of cotton rhizosphere soil, leading to a reduction in the incidence of cotton Verticillium wilt and increasing cotton yield.

Antifungal Activity of Chaetoviridin A from Chaetomium globosum CEF-082 Metabolites Against Verticillium dahliae in Cotton.

Cotton Verticillium wilt (CVW) is a severe soilborne disease caused by the pathogen Verticillium dahliae, and it has a great impact on cotton production. Previous studies found that the biocontrol agent Chaetomium globosum CEF-082 and its metabolic filtrate could reduce the incidence of CVW; however, the underlying mechanism remains unclear. The metabolic crude extract of CEF-082 increased the sensitivity of V. dahliae to stress, degraded the cell wall of V. dahliae, and increased the emergence and plant height of cotton. Through separation and purification of the metabolic crude extract of CEF-082, chaetoviridin A was identified and found to be highly active against V. dahliae. The compound caused cell necrosis and mycelial deformation, increased the production of reactive oxygen species and nitrous oxide, and inhibited the germination of microsclerotia of V. dahliae, enhancing the cotton plant defense response. In addition, CEF-082 also colonized cotton plants.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Cotton GhSSI2 isoforms from the stearoyl acyl carrier protein fatty acid desaturase family regulate Verticillium wilt resistance.

Lipids are major and essential constituents of plant cells and provide energy for various metabolic processes. However, the function of the lipid signal in defence against Verticillium dahliae, a hemibiotrophic pathogen, remains unknown. Here, we characterized 19 conserved stearoyl‐ACP desaturase family proteins from upland cotton (Gossypium hirsutum). We further confirmed that GhSSI2 isoforms, including GhSSI2‐A, GhSSI2‐B, and GhSSI2‐C located on chromosomes A10, D10, and A12, respectively, played a dominant role to the cotton 18:1 (oleic acid) pool. Suppressing the expression of GhSSI2s reduced the 18:1 level, which autoactivated the hypersensitive response (HR) and enhanced cotton Verticillium wilt and Fusarium wilt resistance. We found that low 18:1 levels induced phenylalanine ammonia‐lyase‐mediated salicylic acid (SA) accumulation and activated a SA‐independent defence response in GhSSI2s‐silenced cotton, whereas suppressing expression of GhSSI2s affected PDF1.2‐dependent jasmonic acid (JA) perception but not the biosynthesis and signalling cascade of JA. Further investigation showed that structurally divergent resistance‐related genes and nitric oxide (NO) signal were activated in GhSSI2s‐silenced cotton. Taken together, these results indicate that SA‐independent defence response, multiple resistance‐related proteins, and elevated NO level play an important role in GhSSI2s‐regulated Verticillium wilt resistance. These findings broaden our knowledge regarding the lipid signal in disease resistance and provide novel insights into the molecular mechanism of cotton fungal disease resistance.

Effects of Seed-Coating Preparations of Living Streptomyces globisporus on Plant Growth Promotion and Disease Control against Verticillium Wilt in Cotton

This study explored the role of viable cells and active metabolites in the seed-coating preparations of living Streptomyces globisporus in plant growth promotion and disease control against Verticillium wilt of cotton. Pot experiments were carried out to evaluate the effects of seed coating with living (LA), inactivated (IA), and 10-fold diluted living (DLA) preparations of S. globisporus Act7 and Act28 on plant growth performance and disease index of cotton seedlings under attack by Verticillium dahliae. Compared with the control, leaf greenness was increased by 50.0–70.1% across all the three treatments of Act7 (LA7, IA7, and DLA7), and the leaf area of LA7- and DLA7-treated seedlings was increased by more than twice (p < 0.05). DLA7 also increased shoot weight by 62.2%, while IA7 and DLA7 improved plant biomass by 30.4% and 72.1%, respectively (p < 0.05). The root vitality of IA7- and DLA7-treated seedlings was enhanced by 69.1% and 75.8%, respectively. The disease index of Verticillium wilt was reduced by 31.9% (LA7), 25.0% (IA7), and 66.7% (DLA7) after treatments. The effects of Act28 preparations were similar to those of Act7 preparations. Through the combined action of viable spores and active metabolites, seed coating with an appropriate dose of living S. globisporusan can considerably promote plant growth and improve root vitality, while reducing the incidence of Verticillium wilt in cotton seedlings under attack by V. dahliae.

GhMYB4 downregulates lignin biosynthesis and enhances cotton resistance to Verticillium dahliae.

GhMYB4 acts as a negative regulator in lignin biosynthesis, which results in alteration of cell wall integrity and activation of cotton defense response. Verticillium wilt of cotton (Gossypium hirsutum) caused by the soil-borne fungus Verticillium dahliae (V. dahliae) represents one of the most important constraints of cotton production worldwide. Mining of the genes involved in disease resistance and illuminating the molecular mechanisms that underlie this resistance is of great importance in cotton breeding programs. Defense-induced lignification in plants is necessary for innate immunity, and there are reports of a correlation between increased lignification and disease resistance. In this study, we present an example in cotton whereby plants with reduced lignin content also exhibit enhanced disease resistance. We identified a negative regulator of lignin synthesis, in cotton encoded in GhMYB4. Overexpression of GhMYB4 in cotton and Arabidopsis enhanced resistance to V. dahliae with reduced lignin deposition. Moreover, GhMYB4 could bind the promoters of several genes involved in lignin synthesis, such as GhC4H-1, GhC4H-2, Gh4CL-4, and GhCAD-3, and impair their expression. The reduction of lignin content in GhMYB4-overexpressing cotton led to alterations of cell wall integrity (CWI) and released more oligogalacturonides (OGs) which may act as damage-associated molecular patterns (DAMPs) to stimulate plant defense responses. In support of this hypothesis, exogenous application with polygalacturonic acid (PGA) in cotton activated biosynthesis of jasmonic acid (JA) and JA-mediated defense against V. dahliae, similar to that described for cotton plants overexpressing GhMYB4. This study provides a new candidate gene for cotton disease-resistant breeding and an increased understanding of the relationship between lignin synthesis, OG release, and plant immunity.

Genome-Wide Analysis of Ribosomal Protein GhRPS6 and Its Role in Cotton Verticillium Wilt Resistance.

Verticillium wilt is threatening the world’s cotton production. The pathogenic fungus Verticillium dahliae can survive in the soil in the form of microsclerotia for a long time, colonize through the root of cotton, and invade into vascular bundles, causing yellowing and wilting of cotton leaves, and in serious cases, leading to plant death. Breeding resistant varieties is the most economical and effective method to control Verticillium wilt. In previous studies, proteomic analysis was carried out on different cotton varieties inoculated with V. dahliae strain Vd080. It was found that GhRPS6 was phosphorylated after inoculation, and the phosphorylation level in resistant cultivars was 1.5 times than that in susceptible cultivars. In this study, knockdown of GhRPS6 expression results in the reduction of SA and JA content, and suppresses a series of defensive response, enhancing cotton plants susceptibility to V. dahliae. Overexpression in Arabidopsis thaliana transgenic plants was found to be more resistant to V. dahliae. Further, serines at 237 and 240 were mutated to phenylalanine, respectively and jointly. The transgenic Arabidopsis plants demonstrated that seri-237 compromised the plant resistance to V. dahliae. Subcellular localization in Nicotiana benthamiana showed that GhRPS6 was localized in the nucleus. Additionally, the pathogen inoculation and phosphorylation site mutation did not change its localization. These results indicate that GhRPS6 is a potential molecular target for improving resistance to Verticillium wilt in cotton. This lays a foundation for breeding disease-resistant varieties.

The Role of a New Compound Micronutrient Multifunctional Fertilizer against Verticillium dahliae on Cotton.

Verticillium dahliae Kleb., the causal pathogen of vascular wilt, can seriously reduce the yield and quality of many crops, including cotton (Gossypium hirsutum). To control the harm caused by V. dahliae, considering the environmental pollution of chemical fungicides and their residues, the strategy of plant nutrition regulation is becoming increasingly important as an eco-friendly method for disease control. A new compound micronutrient fertilizer (CMF) found in our previous study could reduce the damage of cotton Verticillium wilt and increase yield. However, there is little information about the mode of action of CMF to control this disease. In the present study, we evaluated the role of CMF against V. dahliae and its mechanism of action in vitro and in vivo. In the laboratory tests, we observed that CMF could inhibit hyphal growth, microsclerotia germination, and reduce sporulation of V. dahliae. Further studies revealed that the biomass of V. dahliae in the root and hypocotyl of cotton seedlings treated with CMF were significantly reduced compared with the control, and these results could explain the decline in the disease index of cotton Verticillium wilt. Furthermore, those key genes involved in the phenylpropanoid metabolism pathway, resistance-related genes defense, and nitric oxide signaling pathway were induced in cotton root and hypocotyl tissue when treated with CMF. These results suggest that CMF is a multifaceted micronutrient fertilizer with roles in inhibiting the growth, development, and pathogenicity of V. dahliae and promoting cotton growth.

The Lethal Effect ofBacillus subtilisZ15 Secondary Metabolites onVerticillium dahliae

Bacillus subtilis Z15 (BS-Z15), isolated from cotton rhizosphere soil, inhibits Verticillium dahliae and suppresses cotton Verticillium wilt in pot experiments. We investigated the influence of environmental factors, pH, temperature, ultraviolet light, protease, and incubation time on the stability of BS-Z15 secondary metabolites (SMs), and the mechanism underlying the cytotoxicity of BS-Z15 SMs on V. dahliae. BS-Z15 and its fermentation broth inhibited V. dahliae, and this effect was mediated by its SMs. These were shown to be stable to the influence of the above environmental factors. BS-Z15 SMs decreased the viability of V. dahliae conidia in a time-dependent manner. Scanning electron microscopy showed that BS-Z15 and its SMs resulted in flattened and depressed conidia. BS-Z15 SMs induced morphological abnormalities in the hyphae, which showed rough aberrant structures, reduced conidiophore production, and accelerated aging. Flow cytometry using Hoechst/propidium iodide double staining revealed that BS-Z15 SMs induced necrosis in V. dahliae in a time-dependent manner. Fluorescence microscopy showed that BS-Z15 SMs did not induce apoptotic bodies in the conidia of V. dahliae but caused significant changes in karyotypes, accompanied by nuclear lysis and nucleic-acid diffusion, which may play important roles in necrosis. In addition, 0.3 mg/mL BS-Z15 SMs had no effect on either the mitochondrial membrane potential or the synthesis of proapoptotic proteins, indicating that the SMs did not induce apoptosis in V. dahliae. Their lethal effect on V. dahliae was by inducing necrosis in its conidia and hyphae. BS-Z15 SMs thus have potential as biological pesticides to control Verticillium wilt in cotton.

Method for estimating inoculum of the soilborne fungal pathogen Verticillium dahliae in Australian cotton soils

The ability to quantify inoculum levels of the soilborne fungal pathogen Verticillium dahliae in field soil is essential for understanding potential disease pressure of Verticillium wilt in cotton and for making informed management decisions. Several semi-selective media and techniques for pathogen isolation have been developed for determining the inoculum levels of V. dahliae present in soil. The objective of this study was to gather data on soil plating techniques, media, sampling depths, and times of sampling for the detection and quantification of V. dahliae in field soils, in order to develop a V. dahliae isolation protocol for Australian cotton-growing soils. Two soil plating techniques (dilution plating or ‘wet plating’, and direct spreading by hand or ‘dry plating’) on four semi-selective media (Sorenson’s NP-10, potato dextrose agar, and acidified versions of each) were compared for their efficacy in quantifying soil inoculum as germinated microsclerotia propagules per gram soil. Soil was sampled from three depths to examine the vertical distribution of the fungus and so determine the ideal sampling depth. Field soil sampling was conducted pre-planting and post-harvest to examine differences in inoculum with sampling time. Based on the results of this study, a soil sampling protocol has been developed for Australian cotton farms that includes sampling soil before planting, at a depth of 2–24 cm, and using the direct dry plating method on Sorenson’s NP-10 media.

Ergosterol-targeting fusion antifungal peptide significantly increases the Verticillium wilt resistance of cotton.

SummaryIncreasing the targeting ability of antifungal proteins towards specific components of fungal cells has the potential to improve their antifungal activity and reduce harmful effects to nontarget cells. To obtain effective disease resistance genes against cotton Verticillium wilt, we constructed several fusion genes, in which binding domains targeting chitin, sphingolipid or ergosterol in the fungal cell wall or cell membrane were individually fused to the antifungal peptide BbAFP1 from entomopathogenic fungus Beauveria bassiana. Transient expression of fusion genes in cotton cotyledons indicated that the BbAFP1::ErBD fusion peptide with an ergosterol binding domain exhibited better disease resistance against V. dahliae than wild‐type BbAFP1 and other fusion genes. BbAFP1::ErBD and BbAFP1 transgenic cotton were obtained and verified by Southern and Western blotting. Compared with BbAFP1‐expressing cotton, BbAFP1::ErBD‐expressing cotton showed higher disease resistance against V. dahliae, with smaller lesion areas (0.07 cm2 vs. 0.16 cm2) on the leaves and a lower disease index (23.9 vs. 34.5). Overexpression of BbAFP1::ErBD by transgenic tobacco also showed enhanced disease resistance against V. dahliae compared with that of the wild‐type gene. These results indicated that construction of fusion antifungal peptides that target fungal cells is a powerful strategy to obtain new anti‐disease genes, and the obtained fusion gene BbAFP1::ErBD has the potential to defend against plant fungal diseases.

A cotton WAKL protein interacted with a DnaJ protein and was involved in defense against Verticillium dahliae

Accumulating evidence indicates that plant cell wall-associated receptor-like kinases (WAKs) involve in defense against pathogen attack, but their related signaling processes and regulatory mechanism remain largely unknown. We identified a WAK-like kinase (GhWAKL) from upland cotton (Gossypium hirsutum) and characterized its functional mechanism. Expression of GhWAKL in cotton plants was induced by Verticillium dahliae infection and responded to the application of salicylic acid (SA). Knockdown of GhWAKL expression results in the reduction of SA content and suppresses the SA-mediated defense response, enhancing cotton plants susceptibility to V. dahliae. And, ecotopic overexpression of GhWAKL in Arabidopsis thaliana conferred plant resistance to the pathogen. Further analysis demonstrated that GhWAKL interacted with a cotton DnaJ protein (GhDNAJ1) on the cell membrane. Silencing GhDNAJ1 also enhanced cotton susceptibility to V. dahliae. Moreover, the mutation of GhWAKL at site Ser628 with the phosphorylation decreased the interaction with GhDNAJ1 and compromised the plant resistance to V. dahliae. We propose that GhWAKL is a potential molecular target for improving resistance to Verticillium wilt in cotton.

Effects of potassium application on soil ecological resistance to Verticillium wilt of cotton (Gossypium hirsutum L.)

ABSTRACT Verticillium wilt (V-wilt) causes huge and irreparable losses to cotton worldwide every year. Potassium (K) is considered to be a critical nutrient for resistance to biotic and abiotic stresses. To verify the effect of K application on the establishment of an ecological-friendly soil microenvironment resistant to V-wilt, a two-year field experiment was conducted. Two cotton varieties (ND-601, resistive and JM-11, sensitive) with different resistance to V-wilt were used in this study, and five different K rates (0, 75, 150, 225, and 300 kg ha−1 K2O) were set for each variety in the field inoculated with Verticillium dahliae (V. dahliae). The results showed that different levels of K application had significant effect on the reduction of cotton V-wilt. K application increased the content of K and total phenolics in rhizosphere soil, but decreased the content of soluble sugar and alanine. Moreover, K application reduced the number of bacteria, fungi, and total microorganisms in rhizosphere soil, especially the number of V. dahliae. In conclusion, K application can create a good micro-ecological environment for the root system by changing the K status, root exudates, and microorganisms in rhizosphere soil, which are beneficial to reduce the symptoms of cotton V-wilt.

Effects of production practices on temporal disease progress of Verticillium wilt of cotton (Gossypium hirsutum L.) in the Texas High Plains, USA

Verticillium wilt of cotton (Gossypium hirsutum L.), caused by the soilborne fungus Verticillium dahliae Kleb., is an economically damaging disease. To date, limited information is available regarding the effects of common production practices on the epidemiology of Verticillium wilt of cotton. Therefore, this study evaluated the effectiveness of different seeding rates and cotton cultivars on suppressing Verticillium wilt and simulate the temporal dynamics of Verticillium wilt in cotton. Field experiments were conducted in 2015 and 2016 at two locations naturally infested with V. dahliae in the Texas High Plains. Results indicated wilt incidence decreased significantly up to 49% when planting partially resistant cotton cultivars at higher seeding rates (9.8–19.5 seeds m−2) at both locations across years (P < 0.05). The area under disease progress curves (AUDPC) increased significantly as seeding rate decreased, and the partially resistant cultivar FiberMax 2484B2F showed a significantly lower AUDPC compared to the susceptible cultivar Deltapine 1212B2RF. Reductions in lint yields by Verticillium wilt, particularly under high disease pressure, could reach 1.03 tons ha−1 (P < 0.05). FiberMax 2484B2F remained significantly lower wilt incidence (23%) than the susceptible cultivar. When characterizing temporal disease progress, nonlinear Gompertz, logistic, and exponential models had better statistical fit (R2) than the linear model (P < 0.05). Under high disease pressure in 2016, the R2 values (0.94 and 0.97 at Quaker and Cone) of the Gompertz model were significantly greater than others. The Gompertz was determined to be the optimal fitting model for simulating the Verticillium wilt epidemics.

Pectin lyase enhances cotton resistance to Verticillium wilt by inducing cell apoptosis of Verticillium dahliae

Verticillium wilt caused by Verticillium dahliae Kleb. is a major disease in cotton. We found that pectin lyase can enhance cotton resistance to Verticillium wilt and induce cell apoptosis of V. dahliae strain Vd080. The biocontrol effect of pectin lyase on Vd080 reached 61.9%. Pectin lyase increased ERG4 (Delta (24 (24 (1)))-sterol reductase) expression, the ergosterol content of the cell membrane, the collapse of mitochondrial membrane potential, hydrogen peroxide content, metacaspase activity, and Ca2+ content in the cytoplasm in the Vd080 strain and induced endoplasmic reticulum (ER) stress. Pectin lyase also increased the expression levels of the ER molecular chaperone glucose regulating protein Grp78 (BiP), protein disulfide isomerase (PDI) and calnexin (CNX), reduced the expression levels of the protein Hsp40. When the PDI and BiP genes of Vd080 were knocked out, the mutants △BiP and △PDI had reduced sensitivity to pectin lyase. In the absence of external stress, ER stress appeared in mutant △BiP cells. Pectin lyase affects the ergosterol content of the Vd080 cell membrane, which causes ER stress and increases the level of BiP to induce Vd080 cell apoptosis. These results demonstrate that pectin lyase can be used to control Verticillium wilt in cotton.

The Cotton BEL1-Like Transcription Factor GhBLH7-D06 Negatively Regulates the Defense Response against Verticillium dahliae.

Verticillium wilt will seriously affect cotton yield and fiber quality. BEL1-Like transcription factors are involved in the regulation of secondary cell wall (SCW) formation, especially the biosynthesis of lignin that also plays a key role in cotton disease resistance. However, there is no report on the role of BEL1-Like transcription factor in the regulation of plant biological stress. In this study, tissue expression pattern analysis showed that a BEL1-Like transcription factor GhBLH7-D06 was predominantly expressed in vascular tissues and the SCW thickening stage of fiber development, while its expression could also respond to Verticillium dahliae infection and the phytohormone MeJA treatment, which indicated that GhBLH7-D06 might be involved in the defense response of Verticillium wilt. Using virus-induced gene silencing (VIGS) technology, we found silencing the expression of GhBLH7-D06 could enhance the resistance of cotton plants to Verticillium wilt, and the acquisition of resistance might be mainly due to the significant overexpression of genes related to lignin biosynthesis and JA signaling pathway, which also proves that GhBLH7-D06 negatively regulates the resistance of cotton to Verticillium wilt. Based on the results of yeast two-hybrid (Y2H) library screening and confirmation by bimolecular fluorescence complementary (BiFC) experiment, we found an Ovate Family Protein (OFP) transcription factor GhOFP3-D13 which was also a negative regulator of cotton Verticillium wilt resistance could that interacts with GhBLH7-D06. Furthermore, the dual-luciferase reporter assay and yeast one-hybrid (Y1H) experiment indicated that GhBLH7-D06 could target binding to the promoter region of GhPAL-A06 to suppress its expression and eventually lead to the inhibition of lignin biosynthesis. In general, the GhBLH7-D06/GhOFP3-D13 complex can negatively regulate resistance to Verticillium wilt of cotton by inhibiting lignin biosynthesis and JA signaling pathway.

A novel peroxiredoxin from the antagonistic endophytic bacterium Enterobacter sp. V1 contributes to cotton resistance against Verticillium dahliae

[Aims] To reveal the molecular mechanism of endophytic bacteria in Verticillium wilt-resistant cottons and deeply understand the interaction between soil and plants. [Methods] Active tracking screening was used for the isolation of antagonistic strain. Morphological and molecular analyses were conducted to determine its phenotypic and genotypic characteristics. MALDI-TOF/TOF MS was employed to identify the antifungal substance. Functional verification was performed by gene cloning, expression, knockout and complementation. [Results] Enterobacter sp. V1 was isolated from Verticillium-wilt-resistant cotton Xinhai 15, which showed significantly antagonistic abilities against cotton verticillium wilt. A peroxiredoxin named ProV1 with virulent against V. dahliae was obtained. The gene for the peroxiredoxin ProV1 was cloned, and the nucleotide sequence showed 85.5% similarity with peroxiredoxin C (WP 096152328) reported from E. hormaeche. The purified heterologously expressed ProV1 indicated strong inhibitory activities. Moreover, the suppression of V. dahliae also decreased in proV1 mutant strain compared with wild type strain. The inhibitory activities could be partially restored by a complementation of proV1 gene in the mutant strain. [Conclusion] The results of this study reveal that a novel peroxiredoxin from an endophytic bacterial strain Enterobacter sp. V1 can serve as a virulent factor against fungi V. dahliae, which helps understanding the interaction between endyphytic bacteria and plant pathogenic fungi, and improving the biological control of cotton Verticillium wilt.

Colonization on Cotton Plants with a GFP Labeled Strain of Bacillus axarquiensis.

Verticillium dahliae was one of the most important diseases caused Verticilliumwiltofcotton. In our previous study, Bacillus axarquiensis TUBP1 was screened and found to be an antagonistic strain against V. dahliae with 43% biocontrol effect in the cotton field. In order to uncover the functional mechanism of B. axarquiensis against Verticillium wilt in cotton, the colonization of B. axarquiensis labeled with a green fluorescent protein (GFP) was investigated in cotton plants and the rhizosphere soil. Firstly, a plasmid (pHT-315) containing gfp gene was successfully transformed into wild B. axarquiensis TUBP1 and labeled a green fluorescence by electroporation, which didn't change the bioactivity in vitro. In gnotobiotic conditions, cotton seeds were then inoculated with the gfp-labeled strain and grown in green house. Observation with a confocal laser scanning microscope and a scanning electron microscope showed that GFP-labeled B. axarquiensis TUBP1 infected cotton roots and widely distributed in epidermis, cortical parenchyma, intercellular spaces, the xylem vessels, and pith cells as well as root hair cells through cracks formed at the lateral root junctions, followed by a slow migration from roots to stems and leaves. Quantitative fluorescence and flow cytometry (FACS) approaches showed a gradual decrease in the number of TUBP1-315gfp with increasing inoculation time. However, TUBP1-315gfp levels were detectable till 45days after planting. In contrast, no fluorescence signal was detected in the non-inoculated groups. Therefore, GFP-labeled B. axarquiensis TUBP1 exhibited colonization in different parts of cotton plants from the rhizosphere soil.

GbAt11 gene cloned from Gossypium barbadense mediates resistance to Verticillium wilt in Gossypium hirsutum

BackgroundGossypium hirsutum is highly susceptible to Verticillium wilt, and once infected Verticillium wilt, its yield is greatly reduced. But G. barbadense is highly resistant to Verticillium wilt. It is possible that transferring some disease-resistant genes from G. barbadense to G. hirsutum may contribute to G. hirsutum resistance to Verticillium wilt.ResultHere, we described a new gene in G. barbadense encoding AXMN Toxin Induced Protein-11, GbAt11, which is specifically induced by Verticillium dahliae in G. barbadense and enhances Verticillium wilt resistance in G. hirsutum. Overexpression in G. hirsutum not only significantly improves resistance to Verticillium wilt, but also increases the boll number per plant. Transcriptome analysis and real-time polymerase chain reaction showed that GbAt11 overexpression can simultaneously activate FLS2, BAK1 and other genes, which are involved in ETI and PTI pathways in G. hirsutum.ConclusionThese data suggest that GbAt11 plays a very important role in resistance to Verticillium wilt in cotton. And it is significant for improving resistance to Verticillium wilt and breeding high-yield cotton cultivars.