Genetic Variation of Monilinia fructicola Population in Korea

Brown rot disease, caused by Monilinia spp., poses a significant threat to pome and stone fruit crops globally, resulting in substantial economic losses during pre- and post-harvest stages. Monilinia fructigena, M. laxa, and M. fructicola are identified as the key agents responsible for brown rot disease. In this study, we employed the amplified fragment length polymorphism (AFLP) method to assess the genetic diversity of 86 strains of Monilinia spp. isolated from major stone fruit cultivation regions in South Korea. Specifically, strains were collected from Chungcheong, Gangwon, Gyeonggi, Gyeongsang, and Jeolla provinces (-do). A comparative analysis of strain characteristics, such as isolation locations, host plants, and responses to chemical fungicides, was conducted. AFLP phylogenetic classification using 20 primer pairs revealed the presence of three distinct groups, with strains from Jeolla province consistently forming a separate group at a high frequency. Furthermore, M. fructicola was divided into three groups by the AFLP pattern. Principal coordinate analysis and PERMANOVA were applied to compare strain information, such as origin, host, and fungicide sensitivity, revealing significant partition patterns for AFLP according to geographic origin and host plants. This study represents the utilization of AFLP methodology to investigate the genetic variability among M. fructicol isolates, highlighting the importance of continuous monitoring and management of variations in the brown rot pathogen.

Unraveling the Role of Cytochrome P450 as a Key Regulator Lantipeptide Production in Streptomyces globisporus

The aim of this study was to investigate the regulation of lantipeptide production in Streptomyces globisporus SP6C4, which produces the novel antifungal lantipeptides conprimycin and grisin, and to identify the role of cytochrome P450 (P450) in tis regulation. To investigate the regulation of lantipeptide production, we created gene deletion mutants, including ΔP450, ΔtsrD, ΔlanM, ΔP450ΔtsrD, and ΔP450ΔlanM. These mutants were characterized in terms of their morphology, sporulation, attachment, and antifungal activity against Fusarium oxysporum. The gene deletion mutants showed distinct characteristics compared to the wild-type strain. Among them, the ΔP450ΔlanM double mutant exhibited a recovery of antifungal activity against F. oxysporum, indicating that P450 plays a significant role in regulating lantipeptide production in S. globisporus SP6C4. Our findings highlight the significant role of P450 in the regulation of lantipeptide production and morphological processes in S. globisporus. The results suggest a potential link between P450-mediated metabolic pathways and the regulation of growth and secondary metabolism in SP6C4, thereby highlighting P450 as a putative target for the development of new antifungal agents.

Dynamics of Bacterial Communities by Apple Tissue: Implications for Apple Health

Herein, we explored the potential of the apple's core microbiota for biological control of Erwinia amylovora, which causes fire blight disease, and analyzed the structure of the apple's bacterial community across different tissues and seasons. Network analysis results showed distinct differences in bacterial community composition between the endosphere and rhizosphere of healthy apples, and eight taxa were identified as negatively correlated with E. amylovora, indicating their potential key role in a new control strategy against the pathogen. This study highlights the critical role of the apple's bacterial community in disease control and provides a new direction for future research in apple production. In addition, the findings suggest that using the composition of the apple's core taxa as a biological control strategy could be an effective alternative to traditional chemical control methods, which have been proven futile and environmentally harmful.

Transition from Ginseng Root Rot Disease-Conducive Soil to -Suppressive Soil Mediated by Pseudomonadaceae

Ginseng is a popular medicinal herb with established therapeutic effects such as cardiovascular disease prevention, anticancer effects, and anti-inflammatory effects. However, the slow growth of ginseng due to soilborne pathogens has been a challenge for establishing new plantations. In this study, we investigated root rot disease associated with the microbiota in a ginseng monoculture model system. Our results showed that a collapse of the early microbiota community inhibiting root rot disease was observed before the disease became severe, and nitrogen fixation was necessary to support the initial microbiota community structure. Furthermore, changes in the nitrogen composition were essential for the suppression of pathogen activity in early monoculture soils. We hypothesize that Pseudomonadaceae, a population built up by aspartic acid, can inhibit the occurrence of root rot disease in ginseng and that specific management practices that maintain a healthy microbiome can be implemented to prevent and mitigate the disease. Our findings provide insights into the potential use of specific members of the microbiota for controlling root rot disease in ginseng cultivation. IMPORTANCE Understanding the initial soil microbiota and community shifts in a monoculture system is critical for developing disease-suppressive soils for crop production. The lack of resistance genes against soilborne pathogens in plants highlights the need for effective management strategies. Our investigation of root rot disease and initial microbiota community shifts in a ginseng monoculture model system provides valuable insight into the development of conducive soil into specific suppressive soil. With a thorough understanding of the microbiota in disease-conducive soil, we can work toward the development of disease-suppressive soil to prevent outbreaks and ensure sustainable crop production.

Analysis of Endophytic Bacterial Communities and Investigation of Core Taxa in Apple Trees

ire blight disease, caused by Erwinia amylovora, is a devastating affliction in apple cultivation worldwide. Chemical pesticides have exhibited limited effectiveness in controlling the disease, and biological control options for treating fruit trees are limited. Therefore, a relatively large-scale survey is necessary to develop microbial agents for apple trees. Here we collected healthy apple trees from across the country to identify common and core bacterial taxa. We analyzed the endophytic bacterial communities in leaves and twigs and discovered that the twig bacterial communities were more conserved than those in the leaves, regardless of the origin of the sample. This finding indicates that specific endophytic taxa are consistently present in healthy apple trees and may be involved in vital functions such as disease prevention and growth. Furthermore, we compared the community metabolite pathway expression rates of these endophyte communities with those of E. amylovora infected apple trees and discovered that the endophyte communities in healthy apple trees not only had similar community structures but also similar metabolite pathway expression rates. Additionally, Pseudomonas and Methylobacterium-Methylorobrum were the dominant taxa in all healthy apple trees. Our findings provide valuable insights into the potential roles of endophytes in healthy apple trees and inform the development of strategies for enhancing apple growth and resilience. Moreover, the similarity in cluster structure and pathway analysis between healthy orchards was mutually reinforcing, demonstrating the power of microbiome analysis as a tool for identifying factors that contribute to plant health.

Mycobiota community and fungal species response to development stage and fire blight disease in apples

Fire blight disease, caused by the bacterial pathogen Erwinia amylovora, has been a significant concern for over 50 countries worldwide. The efficacy of chemical pesticides currently available for disease control is limited. To address this issue, research is being conducted to explore environmentally friendly control methods, particularly biological control using beneficial microorganisms. However, there is limited research on the apple microbiota community and minimal research has been conducted on fungal communities that may exhibit reliable performance in apple trees. Therefore, our objective was to analyze the fungal communities present in apples at different developmental stages and in different tissues, aiming to identify potential biological control agents for fire blight disease. Our findings indicate that the fungal communities present in apple buds, flowers and leaves play an important role in inhibiting the invasion of E. amylovora. Specifically, we propose GS11 and Lipomyces starkeyi as potential keystone taxa that respond to fire blight disease. These findings provide insights into the continuity and discontinuity of fungal community structure in different developmental stages of apples and offer predictions for potential biological control agents for fire blight disease.

Endophytic Streptomyces population induced by L-glutamic acid enhances plant resilience to abiotic stresses in tomato

Endophyte bacteria, which colonize plants including roots, stem, flower, and fruit, it can derive their nutrients from the host, are recognized for their mutualistic relationship with the host plant. They play a critical role in promoting host growth and modulating abiotic stress. Carbon and nitrogen have a significant impact on bacterial population and secondary metabolite production, which are highly specific in various categories such as bacterial growth regulation, anti-compounds production. Application of L-glutamic acid can significantly enhance Streptomyces globisporus population buildup in plants. However, the effectiveness of this population buildup against abiotic stresses such as salinity and drought has not been investigated. Therefore, in this study, we tested the bacteria and their prebiotic activity against salinity and drought stress in tomato plants. Three different amino acids were treated on the tomato plants, and it was observed that L-asparagine and L-proline had a negative effect on plant growth and phenotype, while L-glutamic acid promoted plant growth and increased bacteria population density. The bacteria were found to colonize the rhizosphere and root endosphere, with colonization being promoted by L-glutamic acid. Additionally, Streptomyces was found to have plant growth promotion effects and provided protection against abiotic stresses. Interestingly, L-glutamic acid reduced the damage caused by salinity stress, but not drought stress. These findings suggest that L-glutamic acid plays a role in providing tolerance to salinity stress with the core microbiota, thus the current study demonstrated their prebiotic activity in the agriculture system.

Variations in Kiwifruit Microbiota across Cultivars and Tissues during Developmental Stages

The plant microbiota plays a crucial role in promoting plant health by facilitating the nutrient acquisition, abiotic stress tolerance, biotic stress resilience, and host immune regulation. Despite decades of research efforts, the precise relationship and function between plants and microorganisms remain unclear. Kiwifruit (Actinidia spp.) is a widely cultivated horticultural crop known for its high vitamin C, potassium, and phytochemical content. In this study, we investigated the microbial communities of kiwifruit across different cultivars (cvs. Deliwoong and Sweetgold) and tissues at various developmental stages. Our results showed that the microbiota community similarity was confirmed between the cultivars using principal coordinates analysis. Network analysis using both degree and eigenvector centrality indicated similar network forms between the cultivars. Furthermore, Streptomycetaceae was identified in the endosphere of cv. Deliwoong by analyzing amplicon sequence variants corresponding to tissues with an eigenvector centrality value of 0.6 or higher. Our findings provide a foundation for maintaining kiwifruit health through the analysis of its microbial community.

Roads to Construct and Re-build Plant Microbiota Community

Plant microbiota has influenced plant growth and physiology significantly. Plant and plant-associated microbes have flexible interactions that respond to changes in environmental conditions. These interactions can be adjusted to suit the requirements of the microbial community or the host physiology. In addition, it can be modified to suit microbiota structure or fixed by the host condition. However, no technology is realized yet to control mechanically manipulated plant microbiota structure. Here, we review step-by-step plant-associated microbial partnership from plant growth-promoting rhizobacteria to the microbiota structural modulation. Glutamic acid enriched the population of Streptomyces, a specific taxon in anthosphere microbiota community. Additionally, the population density of the microbes in the rhizosphere was also a positive response to glutamic acid treatment. Although many types of research are conducted on the structural revealing of plant microbiota, these concepts need to be further understood as to how the plant microbiota clusters are controlled or modulated at the community level. This review suggests that the intrinsic level of glutamic acid in planta is associated with the microbiota composition that the external supply of the biostimulant can modulate.

Microbiota Communities of Healthy and Bacterial Pustule Diseased Soybean

Soybean is an important source of protein and for a wide range of agricultural, food, and industrial applications. Soybean is being affected by Xanthomonas citri pv. glycines, a causal pathogen of bacterial pustule disease, result in a reduction in yield and quality. Diverse microbial communities of plants are involved in various plant stresses is known. Therefore, we designed to investigate the microbial community differentiation depending on the infection of X. citri pv. glycines. The microbial community's abundance, diversity, and similarity showed a difference between infected and non-infected soybean. Microbiota community analysis, excluding X. citri pv. glycines, revealed that Pseudomonas spp. would increase the population of the infected soybean. Results of DESeq analyses suggested that energy metabolism, secondary metabolite, and TCA cycle metabolism were actively diverse in the non-infected soybeans. Additionally, Streptomyces bacillaris S8, an endophyte microbiota member, was nominated as a key microbe in the healthy soybeans. Genome analysis of S. bacillaris S8 presented that salinomycin may be the critical antibacterial metabolite. Our findings on the composition of soybean microbiota communities and the key strain information will contribute to developing biological control strategies against X. citri pv. glycines.

Effect of Scenedesmus sp. CHK0059 on Strawberry Microbiota Community

Microalgae are photosynthetic cyanobacteria and eukaryotic microorganisms, mainly living in the water. In agriculture, numerous studies have been conducted to utilize microalgae as a biostimulant resource. Scenedesmus has been known to be one such microalga that can promote plant growth by secretion of auxin or cytokinin hormone analogs. However, no research has been performed on the effect of microalgae treatment on plant microbiota communities. This study was conducted to investigate the mode of action of microalgae as biostimulants in a plant microbiota perspective by using Scenedesmus sp. CHK0059 (also known as species Chlorella fusca), which has been well documented as a biostimulant for strawberries. The strawberry cultivar Keumsil was bred with Seolhyang and Maehyang as the parent cultivars. Using these three cultivars, microbiota communities were evaluated for changes in structural composition according to the CHK0059 treatment. CHK0059-treated Seolhyang, and CHK0059-untreated Maehyang were similar in microbial diversity in the endosphere. From a microbiota community perspective, the diversity change showed that CHK0059 was affected by the characteristics of the host. Conversely, when CHK0059 treatment was applied, populations of Streptomyces and Actinospica were observed in the crown endosphere.

Exploration of Mycobiota in Cypripedium japonicum, an Endangered Species

Orchids live with mycorrhizal fungi in mutualism. This symbiotic relationship plays an essential role in the overall life cycle of orchids from germination, growth, settlement, and reproduction. Among the 1000 species of the orchid, the Korean lady's slipper, Cypripedium japonicum, is known as an endangered species. Currently, only five natural habitats of the Korean lady's slipper remain in South Korea, and the population of Korean lady's slipper in their natural habitat is not increasing. To prevent extinction, this study was designed to understand the fungal community interacting in the rhizosphere of the Korean lady's slipper living in the native and artificial habitats. In-depth analyses were performed to discover the vital mycorrhizal fungi contributing to habitat expansion and cultivation of the endangered orchid species. Our results suggested that Lycoperdon nigrescens contributed most to the increase in natural habitats and Russula violeipes as a characteristic of successful cultivation. And the fungi that helped L. nigrescens and R. violeipes to fit into the rhizosphere community in Korean lady's slipper native place were Paraboeremia selaginellae and Metarhizium anisopliae, respectively. The findings will contribute to restoring and maintaining the endangered orchid population in natural habitats.

Genetic Variation of Strawberry Fusarium Wilt Pathogen Population in Korea

Strawberries are a popular economic crop, and one of the major plantations and exporting countries is Korea in the world. The Fusarium oxysporum species complex (FOSC) is a soil-borne pathogen with genetic diversity, resulting in wilt disease in various crops. In Korea, strawberries wilt disease was first reported in the 1980s due to the infection of FOSC, causing significant economic damage every year. The causal agent, F. oxysporum f. sp. fragariae, is a soil-borne pathogen with a characteristic of FOSC that is difficult to control chemically and mutates easily. This study obtained genetic polymorphism information that was based on AFLP, of F. oxysporum f. sp. fragariae 91 strains, which were isolated from strawberry cultivation sites in Gyeongsangnam-do and Chungcheongnam-do, and compared strains information, which was the isolated location, host variety, response to chemical fungicide, and antagonistic bacteria, and mycelium phenotype. As a result, AFLP phylogeny found that two groups were mainly present, and group B was present at a high frequency in Gyeongsangnam-do. Group B proved less sensitive to tebuconazole than group A through Student's t-test. In addition, the fractions pattern of AFLP was calculated by comparing the strain information using PCA and PERMANOVA, and the main criteria were separated localization and strawberry varieties (PERMANOVA; p < 0.05). And tebuconazole was different with weak confidence (PERMANOVA; p < 0.10). This study suggests that the F. oxysporum f. sp. fragariae should be continuously monitored and managed, including group B, which is less chemically effective.

Glutamic acid reshapes the plant microbiota to protect plants against pathogens

BACKGROUND

Plants in nature interact with other species, among which are mutualistic microorganisms that affect plant health. The co-existence of microbial symbionts with the host contributes to host fitness in a natural context. In turn, the composition of the plant microbiota responds to the environment and the state of the host, raising the possibility that it can be engineered to benefit the plant. However, technology for engineering the structure of the plant microbiome is not yet available.

RESULTS

The loss of diversity and reduction in population density of Streptomyces globisporus SP6C4, a core microbe, was observed coincident with the aging of strawberry plants. Here, we show that glutamic acid reshapes the plant microbial community and enriches populations of Streptomyces, a functional core microbe in the strawberry anthosphere. Similarly, in the tomato rhizosphere, treatment with glutamic acid increased the population sizes of Streptomyces as well as those of Bacillaceae and Burkholderiaceae. At the same time, diseases caused by species of Botrytis and Fusarium were significantly reduced in both habitats. We suggest that glutamic acid directly modulates the composition of the microbiome community.

CONCLUSIONS

Much is known about the structure of plant-associated microbial communities, but less is understood about how the community composition and complexity are controlled. Our results demonstrate that the intrinsic level of glutamic acid in planta is associated with the composition of the microbiota, which can be modulated by an external supply of a biostimulant. Video Abstract.

Comparison of Bacterial Community of Healthy and Erwinia amylovora Infected Apples

Fire blight disease, caused by Erwinia amylovora, could damage rosaceous plants such as apples, pears, and raspberries. In this study, we designed to understand how E. amylovora affected other bacterial communities on apple rhizosphere; twig and fruit endosphere; and leaf, and fruit episphere. Limited studies on the understanding of the microbial community of apples and changes the community structure by occurrence of the fire blight disease were conducted. As result of these experiments, the infected trees had low species richness and operational taxonomic unit diversity when compared to healthy trees. Rhizospheric bacterial communities were stable regardless of infection. But the communities in endosphere and episphere were significanlty affected by E. amylovora infection. We also found that several metabolic pathways differ significantly between infected and healthy trees. In particular, we observed differences in sugar metabolites. The finding provides that sucrose metabolites are important for colonization of E. amylovora in host tissue. Our results provide fundamental information on the microbial community structures between E. amylovora infected and uninfected trees, which will contribute to developing novel control strategies for the fire blight disease.

A Genome-Wide Analysis of Antibiotic Producing Genes in Streptomyces globisporus SP6C4

Soil is the major source of plant-associated microbes. Several fungal and bacterial species live within plant tissues. Actinomycetes are well known for producing a variety of antibiotics, and they contribute to improving plant health. In our previous report, Streptomyces globisporus SP6C4 colonized plant tissues and was able to move to other tissues from the initially colonized ones. This strain has excellent antifungal and antibacterial activities and provides a suppressive effect upon various plant diseases. Here, we report the genome-wide analysis of antibiotic producing genes in S. globisporus SP6C4. A total of 15 secondary metabolite biosynthetic gene clusters were predicted using antiSMASH. We used the CRISPR/Cas9 mutagenesis system, and each biosynthetic gene was predicted via protein basic local alignment search tool (BLAST) and rapid annotation using subsystems technology (RAST) server. Three gene clusters were shown to exhibit antifungal or antibacterial activity, viz. cluster 16 (lasso peptide), cluster 17 (thiopeptide-lantipeptide), and cluster 20 (lantipeptide). The results of the current study showed that SP6C4 has a variety of antimicrobial activities, and this strain is beneficial in agriculture.

Bacterial Community Structure and the Dominant Species in Imported Pollens for Artificial Pollination

Pollination is an essential process for plants to carry on their generation. Pollination is carried out in various ways depending on the type of plant species. Among them, pollination by insect pollinator accounts for the most common. However, these pollinators have be decreasing in population density due to environmental factors. Therefore, use of artificial pollination is increasing. However, there is a lack of information on microorganisms present in the artificial pollens. We showed the composition of bacteria structure present in the artificial pollens of apple, kiwifruit, peach and pear, and contamination of high-risk pathogens was investigated. Acidovorax spp., Pantoea spp., Erwinia spp., Pseudomonas spp., and Xanthomonas spp., which are classified as potential high-risk pathogens, have been identified in imported pollens. This study presented the pollen-associated bacterial community structure, and the results are expected to be foundation for strengthening biosecurity in orchard industry.

Investigation of Fungal Strains Composition in Fruit Pollens for Artificial Pollination

Plants pollination are conducted through various pollinators such as wind, animals, and insects. Recently, the necessity for artificial pollination is drawing attention as the proportion of natural pollinators involved is decreasing over the years. Likewise, the trade in pollen for artificial pollination is also increasing worldwide. Through these imported pollens, many unknown microorganisms can flow from foreign countries. Among them, spores of various fungi present in the particles of pollen can be dispersed throughout the orchard. Therefore, in this study, the composition of fungal communities in imported pollen was revealed, and potential ecological characteristics of the fungi were investigated in four types of imported pollen. Top 10 operational taxonomic unit (OTU) of fungi were ranked among the following groups: Alternaria sp., Cladosporium sp., and Didymella glomerata which belong to many pathogenic species. Through FUNGuild analysis, the proportion of OTUs, which is assumed to be potentially plant pathogens, was higher than 50%, except for apple pollen in 2018. Based on this study of fungal structure, this information can suggest the direction of the pollen quarantine process and contribute to fungal biology in pollen.

Changes in Bacterial Community Structure and Enriched Functional Bacteria Associated With Turfgrass Monoculture

There is increasing attention being paid to utilizing microbial communities to improve plant health while reducing management inputs. Thus, the objectives of this research were to assess changes in the rhizosphere bacterial community structure associated with long-term turfgrass monoculture and to demonstrate the feasibility of using functional bacteria as beneficial biocontrol agents. Large patch disease, caused by the fungal pathogen Rhizoctonia solani AG2-2, is a significant threat to turfgrass cultivation. Rhizosphere samples were collected from 2-, 13- and 25-year turfgrass (Zoysia japonica) monocultures. The 13-year monoculture field had a higher pathogen population density than both the 2- and 25-year monoculture fields. Analyses of the rhizosphere bacterial communities revealed that Streptomyces was dominant in the 2-year field and Burkholderia was enriched in the 25-year field. Based on the culturable rhizosphere bacteria, Streptomyces neyagawaensis J6 and Burkholderia vietnamiensis J10 were obtained from the 2- and 25-year fields, respectively. Application of S. neyagawaensis J6 and B. vietnamiensis J10 led to excellent inhibition of large patch disease as well as enhanced tolerance against drought and temperature stresses. The results showed that the selected bacteria could be developed as biocontrol and abiotic stress tolerance agents for turfgrass cultivation.

Genome-Wide Investigation of 2,4-Diacetylphloroglucinol Protection Genes in Arabidopsis thaliana

The compound 2,4-diacetylphloroglucinol (DAPG) is a well-known secondary metabolite produced by Pseudomonas spp. that are used as biocontrol agents. DAPG displays a remarkably broad spectrum of toxic activity against pathogens of plants. Yet high concentrations of DAPG may also have negative effect on plants, but the phytotoxicity of DAPG is not clearly understood. Here, we used genome-wide activation, tagging Arabidopsis plants as the model plant to investigate the plant response to DAPG. A total of 15 lines were selected as DAPG-tolerant plants from among 62,000 lines investigated. The DAPG-responsible genes were then identified via thermal asymmetric interlaced PCR and quantitative reverse transcription PCR, and the gene ontology analysis showed the distribution of these genes having different biological processes, cellular regulations, and molecular functional properties. Collectively, these findings suggest that plants may rely on several pathways to prevent DAPG phytotoxicity.

Draft genome sequence data of Paenibacillus Polymyxa strain TH2H2, isolated from a tomato flower in Korea

Members of the genus Paenibacillus are known for their production of useful substances, and some species of the genus are recognized to be plant growth-promoting rhizobacteria. Paenibacillus polymyxa TH2H2, isolated from a tomato flower, had antifungal activity. Here, the draft genome sequence of Paenibacillus polymyxa TH2H2 is reported. The 5,983,104-bp genome, with a G+C content of 45.31%, comprised 5,221 protein-coding genes, 64 ribosomal RNA and 100 transfer RNA. Three intact antibiotic biosynthesis gene clusters were identified using antiSMASH. These encoded the antifungal agent fusaricidin and two antibacterial agents, tridecaptin and polymyxin. Sequence data have been deposited in the DDBJ/ENA/GenBank database under the accession number RPDG01000000. The version described in this paper is RPDG00000000.1. The BioProject ID in the GenBank database is PRJNA505713.

First Report of Gray Mold Disease on Endangered Species Cypripedium japonicum

Cypripedium japonicum is known to be the indigenous plant to Korea, Japan, and China. However, C. japonicum represents the most critically endangered plant species in South Korea. The plant is esthetically pleasing due to its flower, which is larger than any other orchidaceous species. Disease symptoms relating to gray mold were observed on C. japonicum in May 2019. The suspected pathogen was successfully isolated from the symptomatic leaf tissue and conducted a pure culture of the fungi. The conidia formed consisted of a colorless or light brown single cell, which was either egg or oval-shaped with a size of 7.1 to 13.4 × 5.2 to 8.6 μm. Molecular phylogenetic relationship analysis was also confirmed that the pathogen concerned belonging to the family of Botrytis cinerea. Therefore, the findings confirmed that the pathogen isolated from C. japonicum was consistent with the unique properties of B. cinerea.

Genome-wide screening antifungal genes in Streptomyces griseus S4-7, a Fusarium wilt disease suppressive microbial agent

Streptomyces is a widely studied bacterial genus, particularly with regard to secondary metabolites and antibiotics production. Streptomyces griseus S4-7 was isolated from a strawberry Fusarium wilt disease suppressive soil, and its biological control ability has been well established. However, the antifungal mechanism of strain S4-7 is not yet fully understood at the molecular and biochemical level. Therefore, in this study we created a random mutant library for strain S4-7 with the Tn5 transposon element to investigate antifungal traits on a genome-wide scale. In total 4646 individual mutant strains were created and 13 mutants were selected based on loss of antifungal activity. The knockout genes were identified as electron transfer oxidoreductase (eto),sigma factor-70(sig70) and nrps by Inverse PCR (I-PCR). eto regulates the geranylgeranyl reductase gene, which is involved in terpenoid-quinone biosynthesis, an important factor in cell fitness. In the △eto strain, expression of wbl, a master regulator of the production of secondary metabolites, was significantly reduced. sig70 is responsible for the cell differentiation sensing mechanism in genus Streptomyces. △nrps showed decreased production of hybrid peptide-polyketide siderophores. These results suggest that S. griseus S4-7 may have various antifungal mechanisms, and each mechanism is essential to maximal antifungal activity.

Investigating the Induced Systemic Resistance Mechanism of 2,4-Diacetylphloroglucinol (DAPG) using DAPG Hydrolase-Transgenic Arabidopsis

Plant immune responses can be triggered by chemicals, microbes, pathogens, insects, or abiotic stresses. In particular, induced systemic resistance (ISR) refers to the activation of the immune system due to a plant's interaction with beneficial microorganisms. The phenolic compound, 2,4-diacetylphloroglucinol (DAPG), which is produced by beneficial Pseudomonas spp., acts as an ISR elicitor, yet DAPG's mechanism in ISR remains unclear. In this study, transgenic Arabidopsis thaliana plants overexpressing the DAPG hydrolase gene (phlG) were generated to investigate the functioning of DAPG in ISR. DAPG was applied onto 3-week-old A. thaliana Col-0 and these primed plants showed resistance to the pathogens Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000. However, in the phlG transgenic A. thaliana, the ISR was not triggered against these pathogens. The DAPG-mediated ISR phenotype was impaired in transgenic A. thaliana plants overexpressing phlG, thus showing similar disease severity when compared to untreated control plants. Furthermore, the DAPG-treated A. thaliana Col-0 showed an increase in their gene expression levels of PDF1.2 and WRKY70 but this failed to occur in the phlG transgenic lines. Collectively, these experimental results indicate that jasmonic acid/ethylene signal-based defense system is effectively disabled in phlG transgenic A. thaliana lines.

Proteomic Reference Map and Comparative Analysis between Streptomyces griseus S4-7 and wbiE2 Transcription Factor-Mutant Strain

Streptomyces griseus S4-7, a well-characterized keystone taxon among strawberry microbial communities, shows exceptional disease-preventing ability. The whole-genome sequence, functional genes, and bioactive secondary metabolites of the strain have been described in previous studies. However, proteomics studies of not only the S4-7 strain, but also the Streptomyces genus as a whole, remain limited to date. Therefore, in the present study, we created a proteomics reference map for S. griseus S4-7. Additionally, analysis of differentially expressed proteins was performed against a wblE2 mutant, which was deficient in spore chain development and did not express an antifungal activity-regulatory transcription factor. We believe that our data provide a foundation for further in-depth studies of functional keystone taxa of the phytobiome and elucidation of the mechanisms underlying plant-microbe interactions, es-pecially those involving the Streptomyces genus.

Absolute Configuration and Antibiotic Activity of Piceamycin

The cultivation of a Streptomyces sp. SD53 strain isolated from the gut of the silkworm Bombyx mori produced two macrolactam natural products, piceamycin (1) and bombyxamycin C (2). The planar structures of 1 and 2 were identified by a combination of NMR, MS, and UV spectroscopic analyses. The absolute configurations were assigned based on chemical and chromatographic methods as well as ECD calculations. A new chromatography-based experimental method for determining the configurations of stereogenic centers β to nitrogen atoms in macrolactams was established and successfully applied in this report. These compounds exhibited significant bioactivities against the silkworm entomopathogen Bacillus thuringiensis and various human pathogens as well as human cancer cell lines. In particular, piceamycin potently inhibited Salmonella enterica and Proteus hauseri with MIC values of 0.083 μg/mL and 0.025 μg/mL, respectively. The biosynthetic pathway involved in the formation of the cyclopentenone moiety in piceamycin is discussed.

Comparison of Microbial Community of Rhizosphere and Endosphere in Kiwifruit

Understanding the microbial community and function are crucial knowledge for crop management. In this study, bacterial and fungal community structures both rhizosphere and endosphere in kiwifruit were analyzed to gain our knowledge in kiwifruit microbiome. Microbial community in rhizosphere was less variation than endosphere community. Functional prediction results demonstrated that abundance of saprotrophic fungi was similar in both rhizosphere and endosphere, but potential pathogenic fungi was more abundance in endosphere than in rhizosphere. This finding suggested that maintain healthy soil is the first priority to protect the host plant against biotic stresses.

A mutualistic interaction between Streptomyces bacteria, strawberry plants and pollinating bees

Microbes can establish mutualistic interactions with plants and insects. Here we track the movement of an endophytic strain of Streptomyces bacteria throughout a managed strawberry ecosystem. We show that a Streptomyces isolate found in the rhizosphere and on flowers protects both the plant and pollinating honeybees from pathogens (phytopathogenic fungus Botrytis cinerea and pathogenic bacteria, respectively). The pollinators can transfer the Streptomyces bacteria among flowers and plants, and Streptomyces can move into the plant vascular bundle from the flowers and from the rhizosphere. Our results present a tripartite mutualism between Streptomyces, plant and pollinator partners.

Characterization of Antibacterial Strains against Kiwifruit Bacterial Canker Pathogen

Kiwifruit (Actinidia spp.) is an economically important crop and a bacterial canker disease, caused by Pseudomonas syringae pv. actinidiae (Psa), is the most destructive disease in kiwifruit production. Therefore, prevent and control of the disease is a critical issue in kiwifruit industry worldwide. Unfortunately, there is no reliable control methods have been developed. Recently, interest in disease control using microbial agents is growing. However, kiwifruit microbiota and their roles in the disease control is mainly remaining unknown. In this study, we secured bacterial libraries from kiwifruit ecospheres (rhizosphere, endospere, and phyllosphere) and screened reliable biocontrol strains against Psa. As the results, Streptomyces racemochromogenes W1SF4, Streptomyces sp. W3SF9 and S. parvulus KPB2 were selected as anti-Psa agents from the libraries. The strains showed forcible antibacterial activity as well as exceptional colonization ability on rhizosphere or phyllosphere of kiwifruit. Genome analyses of the strains suggested that the strains may produce several anti-Psa secondary metabolites. Our results will contribute to develop biocontrol strains against the kiwifruit canker pathogen and the disease management strategies.

Root-associated microbes in sustainable agriculture: models, metabolites and mechanisms

Since the discovery of penicillin in 1928 and throughout the 'age of antibiotics' from the 1940s until the 1980s, the detection of novel antibiotics was restricted by lack of knowledge about the distribution and ecology of antibiotic producers in nature. The discovery that a phenazine compound produced by Pseudomonas bacteria could suppress soilborne plant pathogens, and its recovery from rhizosphere soil in 1990, provided the first incontrovertible evidence that natural metabolites could control plant pathogens in the environment and opened a new era in biological control by root-associated rhizobacteria. More recently, the advent of genomics, the availability of highly sensitive bioanalytical instrumentation, and the discovery of protective endophytes have accelerated progress toward overcoming many of the impediments that until now have limited the exploitation of beneficial plant-associated microbes to enhance agricultural sustainability. Here, we present key developments that have established the importance of these microbes in the control of pathogens, discuss concepts resulting from the exploration of classical model systems, and highlight advances emerging from ongoing investigations. © 2019 Society of Chemical Industry.

Valinomycin, produced by Streptomyces sp. S8, a key antifungal metabolite in large patch disease suppressiveness

Large patch disease, caused by Rhizoctonia solani AG2-2, is the most devastating disease in Zoysiagrass (Zoysia japonica). Current large patch disease control strategies rely primarily upon the use of chemical pesticides. Streptomyces sp. S8 is known to possess exceptional antagonistic properties that could potentially suppress the large patch pathogen found at turfgrass plantations. This study aims to demonstrate the feasibility of using the strain as a biological control mechanism. Sequencing of the S8 strain genome revealed a valinomycin biosynthesis gene cluster. This cluster is composed of the vlm1 and vlm2 genes, which are known to produce antifungal compounds. In order to verify this finding for the large patch pathogen, a valinomycin biosynthesis knockout mutant was created via the CRISPR/Cas9 system. The mutant lost antifungal activity against the large patch pathogen. Consequently, it is anticipated that eco-friendly microbial preparations derived from the S8 strain can be utilized to biologically control large patch disease.

Function and Distribution of a Lantipeptide in Strawberry Fusarium Wilt Disease-Suppressive Soils

Streptomyces griseus S4-7 is representative of strains responsible for the specific soil suppressiveness of Fusarium wilt of strawberry caused by Fusarium oxysporum f. sp. fragariae. Members of the genus Streptomyces secrete diverse secondary metabolites including lantipeptides, heat-stable lanthionine-containing compounds that can exhibit antibiotic activity. In this study, a class II lantipeptide provisionally named grisin, of previously unknown biological function, was shown to inhibit F. oxysporum. The inhibitory activity of grisin distinguishes it from other class II lantipeptides from Streptomyces spp. Results of quantitative reverse transcription-polymerase chain reaction with lanM-specific primers showed that the density of grisin-producing Streptomyces spp. in the rhizosphere of strawberry was positively correlated with the number of years of monoculture and a minimum of seven years was required for development of specific soil suppressiveness to Fusarium wilt disease. We suggest that lanM can be used as a diagnostic marker of whether a soil is conducive or suppressive to the disease.

Construction of a proteome reference map and response of Gaeumannomyces graminis var. tritici to 2,4-diacetylphloroglucinol

Take-all disease, caused by Gaeumannomyces graminis var. tritici (Ggt), is one of the most serious root diseases in wheat production. In this study, a proteomic platform based on 2-dimensional gel electrophoresis (2-DE) and Matrix-Assisted Laser Desorption/Ionization Time of Flight Tandem Mass Spectrometry (MALDI-TOF/TOF MS) was used to construct the first proteome database reference map of G. graminis var. tritici and to identify the response of the pathogen to 2,4-diacetylphloroglucinol (DAPG), which is a natural antibiotic produced by antagonistic Pseudomonas spp. in take-all suppressive soils. For mapping, a total of 240 spots was identified that represented 209 different proteins. The most abundant biological function categories in the Ggt proteome were related to carbohydrate metabolism (21%), amino acid metabolism (15%), protein folding and degradation (12%), translation (11%), and stress response (10%). In total, 51 Ggt proteins were affected by DAPG treatment. Based on gene ontology, carbohydrate metabolism, amino acid metabolism, stress response, and protein folding and degradation proteins were the ones most modulated by DAPG treatment. This study provides the first extensive proteomic reference map constructed for Ggt and represents the first time that the response of Ggt to DAPG has been characterized at the proteomic level.

Comparison of Endophytic Microbial Community in Kiwifruit Plant Cultivars

The microbiome makes a significant contribution to plant health and endophytes may generate positive effects for the host. However, there is a limited knowledge available concerning the kiwifruit endophyte. Therefore, we discuss endophyte microbiome community structures among the kiwifruit cultivars. Total reads numbered 17620 in cv. Hayward, 11515 in cv. Haegeum and 13613 in cv. Jecygold. The number of OTUs was follows: 112 in cv. Hageum; and 87 in cvs. Hayward and Jecygold. Most of the identified OTUs were phylum Proteobacteria and it emerged that Actinobacteria, Firmicute and Bacteroidetes were mainly present. While the largest difference in Proteobacteria content is between cv. Haegeum and cv. Jecygold, they shared more OTUs than cv. Hayward. As well, this study revealed the presence of remarkably dominated OTU of Pseudomonas spp. in kiwifruit sap regardless of cultivars. To the best of our knowledge, this study is the first tone to investigate the kiwifruit endophyte-microbiome community.

Development qRT-PCR Protocol to Predict Strawberry Fusarium Wilt Occurrence

Strawberry Fusarium wilt disease, caused by Fusarium oxysporum f. sp. fragariae, is the most devastating disease in strawberry production. The pathogen produces chlamydospores which tolerate against harsh environment, fungicide and survive for decades in soil. Development of detection and quantification techniques are regarded significantly in many soilborne pathogens to prevent damage from diseases. In this study, we improved specific-quantitative primers for F. oxysporum f. sp. fragariae to reveal correlation between the pathogen density and the disease severity. Standard curve r2 value of the specific-quantitative primers for qRT-PCR and meting curve were over 0.99 and 80.5°C, respectively. Over pathogen 105 cfu/g of soil was required to cause the disease in both lab and field conditions. With the minimum density to develop the wilt disease, the pathogen affected near 60% in nursery plantation. A biological control microbe agent and soil solarization reduced the pathogen population 2-fold and 1.5-fold in soil, respectively. The developed F. oxysporum f. sp. fragariae specific qRT-PCR protocol may contribute to evaluating soil healthiness and appropriate decision making to control the disease.

Caryolan-1-ol, an antifungal volatile produced by Streptomyces spp., inhibits the endomembrane system of fungi

Streptomyces spp. have the ability to produce a wide variety of secondary metabolites that interact with the environment. This study aimed to discover antifungal volatiles from the genus Streptomyces and to determine the mechanisms of inhibition. Volatiles identified from Streptomyces spp. included three major terpenes, geosmin, caryolan-1-ol and an unknown sesquiterpene. antiSMASH and KEGG predicted that the volatile terpene synthase gene clusters occur in the Streptomyces genome. Growth inhibition was observed when fungi were exposed to the volatiles. Biological activity of caryolan-1-ol has previously not been investigated. Fungal growth was inhibited in a dose-dependent manner by a mixture of the main volatiles, caryolan-1-ol and the unknown sesquiterpene, from Streptomyces sp. S4–7. Furthermore, synthesized caryolan-1-ol showed similar antifungal activity. Results of chemical-genomics profiling assays showed that caryolan-1-ol affected the endomembrane system by disrupting sphingolipid synthesis and normal vesicle trafficking in the fungi.

Comparison of Microbial Community Structure in Kiwifruit Pollens

Flowers of kiwifruit are morphologically hermaphroditic and survivable binucleate pollen is produced by the male flowers. In this study, we investigated microbial diversity in kiwifruit pollens by analyzing amplicon sequences of 16S rRNA. Four pollen samples were collected: 'NZ' was imported from New Zealand, 'CN' from China in year of 2014, respectively. 'KR13' and 'KR14' were collected in 2013' and 2014' in South Korea. Most of the identified bacterial phyla in the four different pollens were Proteobacteria, Actinobacteria and Firmicutes. However, the imported and the domestic pollen samples showed different aspects of microbial community structures. The domestic pollens had more diverse in diversity than the imported samples. Among top 20 OTUs, Pseudomonas spp. was the most dominant specie. Interestingly, a bacterial pathogen of kiwifruit canker, Pseudomonas syringae pv. actinidiae was detected in 'NZ' by the specific PCR. This study provides insights microbial distribution and community structure information in kiwifruit pollen.

Proteomic Analysis of Coprinopsis cinerea under Conditions of Horizontal and Perpendicular Gravity

Coprinopsis cinerea was employed to investigate the fungal response to gravity. Mycelium growth revealed a consistent growth pattern, irrespective of the direction of gravity (i.e., horizontal vs. perpendicular). However, the fruiting body grew in the direction opposite to that of gravity once the primordia had formed. For the proteomic analysis, only curved-stem samples were used. Fifty-one proteins were identified and classified into 13 groups according to function. The major functional groups were hydrolases and transferases (16%), signal transduction (15%), oxidoreductases and isomerases (11%), carbohydrate metabolism (9%), and transport (5%). To the best of our knowledge, this is the first report on a proteomic approach to evaluate the molecular response of C. cinerea to gravity.

Distribution of Rhizosphere and Endosphere Fungi on the First-Class Endangered Plant Cypripedium japonicum

Endangered native plant habitats and populations are rapidly disappearing because of climate and environmental changes. As a representative, the abundance of the first-class endangered wild plant, Cypripedium japonicum, has been rapidly decreasing in Korea. The purpose of this study was to evaluate the distribution of rhizosphere and endophytic fungi on C. japonicum in its native habitat. A total of 440 rhizosphere and 79 endosphere fungi isolates were isolated and identified on the basis of their molecular characteristics. Sixty-five genera and 119 fungi species were identified in this study. The genus Trichoderma showed the highest abundance among both rhizosphere and endosphere fungi. Mortierella, Hypocrea, and Penicillium spp. were also relatively dominant species on C. japonicum. The community structures of rhizosphere and endosphere fungi were similar, but endosphere fungi showed greater diversity.

wblE2 transcription factor in Streptomyces griseus S4-7 plays an important role in plant protection

Streptomyces griseus S4‐7 was originally isolated from the strawberry rhizosphere as a microbial agent responsible for Fusarium wilt suppressive soils. S. griseus S4‐7 shows specific and pronounced antifungal activity against Fusarium oxysporum f. sp. fragariae. In the Streptomyces genus, the whi transcription factors are regulators of sporulation, cell differentiation, septation, and secondary metabolites production. wblE2 function as a regulator has emerged as a new group in whi transcription factors. In this study, we reveal the involvement of the wblE2 transcription factor in the plant‐protection by S. griseus S4‐7. We generated ΔwblE, ΔwblE2, ΔwhiH, and ΔwhmD gene knock‐out mutants, which showed less antifungal activity both in vitro and in planta. Among the mutants, wblE2 mutant failed to protect the strawberry against the Fusarium wilt pathogen. Transcriptome analyses revealed major differences in the regulation of phenylalanine metabolism, polyketide and siderophore biosynthesis between the S4‐7 and the wblE2 mutant. The results contribute to our understanding of the role of streptomycetes wblE2 genes in a natural disease suppressing system.

Screening and investigation Lactobacillius spp. to improve Secale cereale silage quality

Silage is a high-moisture-content forage that is used to feed livestock. Using silage as feed is economically feasible and suitable for cattle management. Secale cereale is considered as a high-quality forage plant. After the heading stage the biomass of S. cereale increases by up to 30%; however, lignification in the cell wall causes low fermentation efficiency and coefficient digestibility, and it may also be contaminated by mycotoxin-producing fungi and can impair the quality of the silage. Therefore, the aim of this study was to screen beneficial Lactobacillius spp. for S. cereale silage to reduce fungi contamination and to increase fibrinolytic ability in the silage. Up to 100 days fermentation period and total 180 lactic acid bacteria were isolated and only a single isolate, R4-26, showed strong acidification ability and antifungal activities against mycotoxin-producing fungus. According to quantitative RT-PCR results, the mycotoxin-producing fungal contamination was significantly reduced in the S. cereale silage containing the R4-26 isolate. In enzymatic assays, only a single isolate, R48-27 demonstrated cellulase, xylanase, chitinase and esterase activities. In conclusion, the beneficial Lactobacillius spp. strains have the ability to reduce mycotoxigenic fungi contamination and increase fibrinolytic activity to improve quality of the S. cereale silage.

Investigation of Genetic Diversity of Fusarium oxysporum f. sp. fragariae Using PCR-RFLP

Fusarium wilts of strawberry, caused by Fusarium oxysporum f. sp. fragariae, is a serious soil-borne disease. Fusarium wilt causes dramatic yield losses in commercial strawberry production and it is a very stubborn disease to control. Reliable chemical control of strawberry Fusarium wilt disease is not yet available. Moreover, other well-known F. oxysporum have different genetic information from F. oxysporum f. sp. fragariae. This analysis investigates the genetic diversity of strawberry Fusairum wilt pathogen. In total, 110 pathogens were isolated from three major strawberry production regions, namely Sukok, Hadong, Sancheong in Gyeongnam province in South Korea. The isolates were confirmed using F. oxysporum f. sp. fragariae species-specific primer sets. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses were executed using the internal transcribed spacer, intergenic spacer, translation elongation factor1-α, and β-tubulin genes of the pathogens and four restriction enzymes: AluI, HhaI, HinP1I and HpyCH4V. Regarding results, there were diverse patterns in the three gene regions except for the β-tubulin gene region. Correlation analysis of strawberry cultivation region, cultivation method, variety, and phenotype of isolated pathogen, confirmed that genetic diversity depended on the classification of the cultivated region.

Complete genome sequence and functional study of the fibrinolytic enzyme-producing bacterium Leuconostoc holzapfelii 5H4, a silage probiotic

To process silage, rye is usually removed before the heading stage but the rye biomass increased up to 30% after the heading stage. However, after the heading stage, lignification rapidly accelerated and it resulted in a poor NDF digestibility problem. This has led to a demand for a strong fibrinolytic enzyme-producing probiotic for rye silage. The Gram-positive Leuconostoc holzapfelii 5H4 was selected as a fibrinolytic enzyme-producing probiotic to overcome lignification of rye silage. The L. holzapfelii 5H4 has a relatively small circular chromosome (1,885,398 bp), but the strain has one cellulase, two xylanase, and five esterase in its genome sequence. All fibrinolytic enzyme genes were relatively highly expressed compared to housekeeping genes, and this was confirmed by qRT-PCR. In this study, we report the complete genome sequence of the bacterium so that fibrinolytic enzyme production and its fibrinolytic activity mechanism are better understood.

Signaling pathways coordinating the alkaline pH response confer resistance to the hevein-type plant antimicrobial peptide Pn-AMP1 in Saccharomyces cerevisiae

Genome-wide screening of Saccharomyces cerevisiae revealed that signaling pathways related to the alkaline pH stress contribute to resistance to plant antimicrobial peptide, Pn-AMP1. Plant antimicrobial peptides (AMPs) are considered to be promising candidates for controlling phytopathogens. Pn-AMP1 is a hevein-type plant AMP that shows potent and broad-spectrum antifungal activity. Genome-wide chemogenomic screening was performed using heterozygous and homozygous diploid deletion pools of Saccharomyces cerevisiae as a chemogenetic model system to identify genes whose deletion conferred enhanced sensitivity to Pn-AMP1. This assay identified 44 deletion strains with fitness defects in the presence of Pn-AMP1. Strong fitness defects were observed in strains with deletions of genes encoding components of several pathways and complex known to participate in the adaptive response to alkaline pH stress, including the cell wall integrity (CWI), calcineurin/Crz1, Rim101, SNF1 pathways and endosomal sorting complex required for transport (ESCRT complex). Gene ontology (GO) enrichment analysis of these genes revealed that the most highly overrepresented GO term was "cellular response to alkaline pH". We found that 32 of the 44 deletion strains tested (72 %) showed significant growth defects compared with their wild type at alkaline pH. Furthermore, 9 deletion strains (20 %) exhibited enhanced sensitivity to Pn-AMP1 at ambient pH compared to acidic pH. Although several hundred plant AMPs have been reported, their modes of action remain largely uncharacterized. This study demonstrates that the signaling pathways that coordinate the adaptive response to alkaline pH also confer resistance to a hevein-type plant AMP in S. cerevisiae. Our findings have broad implications for the design of novel and potent antifungal agents.

Proteomic analyses of the interaction between the plant-growth promoting rhizobacterium Paenibacillus polymyxa E681 and Arabidopsis thaliana

Plant growth-promoting rhizobacteria (PGPR) facilitate the plant growth and enhance their induced systemic resistance (ISR) against a variety of environmental stresses. In this study, we carried out integrative analyses on the proteome, transcriptome, and metabolome to investigate Arabidopsis root and shoot responses to the well-known PGPR strain Paenibacillus polymyxa (P. polymyxa) E681. Shoot fresh and root dry weights were increased, whereas root length was decreased by treatment with P. polymyxa E681. 2DE approach in conjunction with MALDI-TOF/TOF analysis revealed a total of 41 (17 spots in root, 24 spots in shoot) that were differentially expressed in response to P. polymyxa E681. Biological process- and molecular function-based bioinformatics analysis resulted in their classification into seven different protein groups. Of these, 36 proteins including amino acid metabolism, antioxidant, defense and stress response, photosynthesis, and plant hormone-related proteins were up-regulated, whereas five proteins including three carbohydrate metabolism- and one amino acid metabolism-related, and one unknown protein were down-regulated, respectively. A good correlation was observed between protein and transcript abundances for the 12 differentially expressed proteins during interactions as determined by qPCR analysis. Metabolite analysis using LC-MS/MS revealed highly increased levels of tryptophan, indole-3-acetonitrile (IAN), indole-3-acetic acid (IAA), and camalexin in the treated plants. Arabidopsis plant inoculated P. polymyxa E681 also showed resistance to Botrytis cinerea infection. Taken together these results suggest that P. polymyxa E681 may promote plant growth by induced metabolism and activation of defense-related proteins against fungal pathogen.

Epidemiology and Control of Strawberry Bacterial Angular Leaf Spot Disease Caused by Xanthomonas fragariae

Strawberry bacterial angular leaf spot (ALS) disease, caused by Xanthomonas fragariae has become increasingly problematic in the strawberry agro-industry. ALS causes small angular water-soaked lesions to develop on the abaxial leaf surface. Studies reported optimum temperature conditions for X. fragariae are 20°C and the pathogen suffers mortality above 32°C. However, at the nursery stage, disease symptoms have been observed under high temperature conditions. In the present study, results showed X. fragariae transmission was via infected maternal plants, precipitation, and sprinkler irrigation systems. Systemic infections were detected using X. fragariae specific primers 245A/B and 295A/B, where 300-bp and 615-bp were respectively amplified. During the nursery stage (from May to August), the pathogen was PCR detected only in maternal plants, but not in soil or irrigation water through the nursery stage. During the cultivation period, from September to March, the pathogen was detected in maternal plants, progeny, and soil, but not in water. Additionally, un-infected plants, when planted with infected plants were positive for X. fragariae via PCR at the late cultivation stage. Chemical control for X. fragariae with oxolinic acid showed 87% control effects against the disease during the nursery period, in contrast to validamycin-A, which exhibited increased efficacy against the disease during the cultivation stage (control effect 95%). To our knowledge, this is the first epidemiological study of X. fragariae in Korean strawberry fields.

Lichen-forming fungus Caloplaca flavoruscens inhibits transcription factors and chromatin remodeling system in fungi

Lichen-forming fungi and extracts derived from them have been used as alternative medicine sources for millennia and recently there has been a renewed interest in their known bioactive properties for anticancer agents, cosmetics and antibiotics. Although lichen-forming fungus-derived compounds are biologically and commercially valuable, few studies have been performed to determine their modes of action. This study used chemical-genetic and chemogenomic high-throughput analyses to gain insight into the modes of action of Caloplaca flavoruscens extracts. High-throughput screening of 575 lichen extracts was performed and 39 extracts were identified which inhibited yeast growth. A C. flavoruscens extract was selected as a promising antifungal and was subjected to genome-wide haploinsufficiency profiling and homozygous profiling assays. These screens revealed that yeast deletion strains lacking Rsc8, Pro1 and Toa2 were sensitive to three concentrations (IC25.5, IC25 and IC50, respectively) of C. flavoruscens extract. Gene-enrichment analysis of the data showed that C. flavoruscens extracts appear to perturb transcription and chromatin remodeling.