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EPS66A was derived from an unidentified Streptomyces sp. HL-66 by chemical fraction and disease-resistance assays. It was identified as a polysaccharide through a series of chemical characterization, including infrared spectrum analysis, methylation, gas chromatography-mass spectrometry, nuclear magnetic resonance, and high-performance gel permeation chromatography. To determine its effect in plant, EPS66A was applied to tobacco leaves infected with TMV, resulting in the plant with enhanced systemic resistance with a significant reduction of TMV severity. Plant defense was confirmed by early responses, including hypersensitive response (HR) indicated by programed cell death, moderate alkalization, oxidative burst, increase in nitric oxide (NO) and salicylic acid (SA). Furthermore, EPS66A induced callose deposition to form defense barriers against pathogen invasion and the expression of pathogenesis-related (PR) genes, which confirmed the second level of plant defense. Therefore, EPS66A served as a resistance inducer, which was reorganized by tobacco cells that triggered the production of signal molecules. The signals moved in long distance and systemically in plant, which coordinated the expression of defense responses. The study provided a new perspective in understanding the mechanism of EPS66A in regulating plants on environmental adaptability and provided a theoretical foundation for designing safe and sustainable pesticides., (Copyright © 2022 Elsevier B.V. All rights reserved.)

There are various types of compounds studied and applied for plant disease management, and some of them are environment friendly and suitable in organic production. An example is indole-3-carboxaldehyde (A1) and indole-3-carboxylic acid (A2) derived from Purpureocillium lilacinum H1463, which have shown a strong activity in the control of tobacco mosaic virus (TMV). In this study, the effects of these compounds were studied on suppressing TMV and corresponding mechanism. Both A1 and A2 exhibited strong anti-TMV activities in vitro and in vivo. They fractured TMV virions and forced the fractured particles agglomerated. A1 and A2 also induced immune responses or resistance of tobacco to TMV infection, including expressing hypersensitive reaction (HR), increasing defense-related enzymes and overexpressing pathogenesis-related (PR) proteins. The upregulation of salicylic acid (SA) biosynthesis genes PAL, ICS, and PBS3 confirmed that SA served as a defense-related signal molecule. Therefore, indole derivatives have a potential for activating defense of tobacco against TMV and other pathogens and can be used for disease control., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Plant virus diseases have seriously damaged global food security. However, current antiviral agents are not efficient enough for the requirement of agriculture production. So, developing new efficient and nontoxic antiviral agents is imperative. GP-1, from Streptomyces kanasensis ZX01, is a new antiviral glycoprotein, of which the antiviral activity and the mode of action against Tobacco mosaic virus (TMV) were investigated in this study. The results showed that GP-1 could fracture TMV particles, and the infection and accumulation of TMV in host plants were inhibited. Moreover, GP-1 could induce systematic resistance against TMV in the host, according to the results of activities of defensive enzymes increasing, MDA decreasing and overexpression of pathogenesis-related proteins. Furthermore, GP-1 could promote growth of the host plant. In conclusion, GP-1 showed the ability to be developed as an efficient antiviral agent and a fertilizer for agriculture., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A novel glycoprotein GP-1 with antiviral activity against plant virus was isolated from the fermentation broth of the actinomycete Streptomyces sp. ZX01. MALDI-TOF-MS proved that molecular weight of GP-1 approximately was 8.5 kDa. GP-1 was a heat-sensitive glycoprotein with decreasing antiviral activity after treated from 80 °C to 100 °C for 30 min. GP-1 contained 40.23% carbohydrate with N-linked and O-linked glycan. FT-IR and NMR spectra proved that GP-1 contained protein and carbohydrate portions with α- d -(1,6)-glucose residues. Circular dichroism revealed that GP-1 was a glycoprotein with a large unordered content. Moreover, protein sequencing was predicted by using MALDI-TOF-MS and Mascot search. These results suggested that glycoprotein GP-1 could be used as a novel natural antiviral agent in agricultural industry. [ABSTRACT FROM AUTHOR]

GP-1, a novel glycoprotein from Streptomyces sp. ZX01 has a plant immunity-inducing effect. GP-1-treated plants exhibited enhanced systemic resistance with a significant reduction in TMV lesions on tobacco leaves, but its antiviral mechanism remains unclear. In this study, early plant defense-related responses, such as Ca2+ influx, callose apposition, oxidative burst, hypersensitive response, programmed cell death, increase in nitric oxide (NO), and stomatal closure, were investigated under GP-1 treatment, and the mechanism of how GP-1 induces viral resistance in Nicotiana benthamiana was studied. Results showed that GP-1 induced [Ca2+] cyt rapidly in tobacco leaves and suspended cells, followed by reactive oxygen species (ROS) and NO elevation. Transcriptome analysis showed significant differences in expression levels between the GP-1-treated N. benthamiana and the control and showed significantly upregulated and enriched pathways including defense and immune reaction. Similar to typical pathogen-associated molecular patterns, GP-1 induced callose deposition and stomatal closure to form defense barriers against pathogen invasion. The expression of defense-related genes further confirmed the above conclusions. By analyzing transcriptome in N. benthamiana and the contents of salicylic acid (SA) and jasmonic acid (JA), GP-1 enhanced viral resistance of tobacco by improving the SA and JA contents, strengthening plant secondary metabolites activities, promoting systemic accumulation of pathogenesis-related proteins in TMV- inoculated tobacco there by producing antiviral activity. Unlabelled Image • GP-1 is a novel glycoprotein elicitor that has high activity in enhancing plant defense against tobacco mosaic virus (TMV). • GP-1 triggers [Ca2+] cyt elevation, NO and H 2 O 2 production. • GP-1 induced early plant defense-related responses. • Jasmonic acid (JA) and salicylic acid (SA) signal pathways were activated by GP-1, probably through ROS mediation. [ABSTRACT FROM AUTHOR]