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Fungal diseases of plants are one of the key factors causing global crop losses. In this study, we isolated a Bacillus velezensis strain VC3, which was found to have a broad-spectrum inhibitory effect on a variety of phytopathogenic fungi through in vitro and in planta experiments, especially on Magnaporthe oryzae and Colletotrichum gloeosporioides. Further genomic and transcriptomic analyses revealed that the B. velezensis VC3 has multiple functional gene clusters encoding for the synthesis of a variety of antifungal secondary metabolites, including antimicrobial peptides (AMPs) and lipopeptides (LPs). In addition, AMPs and LPs were isolated and purified from B. velezensis VC3 fermentation broth and their antifungal activities were verified in this study. AMPs and LPs significantly inhibited spore germination, appressorium formation, and disease development, and AMPs have a better potential for controlling M. oryzae and C. gloeosporioides than LPs. These findings open new avenues for utilizing B. velezensis VC3 as biocontrol agents, providing potential sustainable solutions for agricultural production. [ABSTRACT FROM AUTHOR]

Pepper anthracnose caused by Colletotrichum gloeosporioides infection is an important fungal disease and represents a serious threat to pepper yield and quality. At present, the pathogenic molecular mechanism of C. gloeosporioides is not very clear. In our study, we characterized the function of C. gloeosporioides CgNis1, a homolog of Magnaporthe oryzae MoNis1. We found that the ∆Cgnis1 mutant reduced the growth rate and was defective in conidiation. Although the rate of appressorium formation was unaffected, the germ tube was found to be abnormal. CgNis1 was shown to be involved in the H2O2 stress response and maintaining cell membrane permeability. The pathogenicity assays performed in this study indicated that the deletion of CgNIS1 is associated with virulence. Our results indicate that CgNis1 is necessary for the growth, development, and pathogenicity of the fungus. This work provides an in-depth analysis of the Nis1 protein, helps to enhance studies on pathogen-related molecular mechanisms, and provides a theoretical basis for the prevention and control of C. gloeosporioides in peppers. [ABSTRACT FROM AUTHOR]

Previous research has shown that the pathogenicity and appressorium development of Magnaporthe oryzae can be inhibited by the ATP synthase subunit beta (Atp2) present in the photosynthetic bacterium Rhodopseudomonas palustris. In the present study, transgenic plants overexpressing the ATP2 gene were generated via genetic transformation in the Zhonghua11 (ZH11) genetic background. We compared the blast resistance and immune response of ATP2-overexpressing lines and wild-type plants. The expression of the Atp2 protein and the physiology, biochemistry, and growth traits of the mutant plants were also examined. The results showed that, compared with the wild-type plant ZH11, transgenic rice plants heterologously expressing ATP2 had no significant defects in agronomic traits, but the disease lesions caused by the rice blast fungus were significantly reduced. When infected by the rice blast fungus, the transgenic rice plants exhibited stronger antioxidant enzyme activity and a greater ratio of chlorophyll a to chlorophyll b. Furthermore, the immune response was triggered stronger in transgenic rice, especially the increase in reactive oxygen species (ROS), was more strongly triggered in plants. In summary, the expression of ATP2 as an antifungal protein in rice could improve the ability of rice to resist rice blast. [ABSTRACT FROM AUTHOR]

Summary: Although many biocontrol bacteria can be used to improve plant tolerance to stresses and to promote plant growth, the hostile environmental conditions on plant phyllosphere and the limited knowledge on bacterial colonization on plant phyllosphere minimized the beneficial effects produced by the biocontrol bacteria. Rhodopseudomonas palustris strain GJ‐22 is known as a phyllosphere biocontrol agent. In this paper, we described detailed processes of strain GJ‐22 colony establishment at various colonization stages. Four different types of bacterial colonies, Type 1, scattered single cells; Type 2, small cell clusters; Type 3, small cell aggregates; and Type 4, large cell aggregates, were observed in the course of bacterial colonization. We categorized bacterial colonization into four phases, which were, Phase I: bacterial colony exists as Type 1 and cell population reduced quickly; Phase II: Type 1 evolved into Type 2 and cell population remained steady; Phase III: Type 3 arose and replaced Type 2, and cell population expanded slowly; and Phase IV: Type 3 matured into Type 4 and cell population increased quickly. We have shown that the preferable location sites of bacterial aggregates on leaf phyllosphere are grooves between plant epidermal cells. Analyses of expressions of plant defence‐related genes showed that, starting from Phase III, bacterial cells in the Type 3 and Type 4 colonies produced unidentified signals to induce host defence against Tobacco mosaic virus infection. In addition, we determined the crucial role of aggregates formation of GJ‐22 cell on plant phyllosphere in terms of bacterial cell stress tolerance and ISR (induced systemic resistance) priming. To our knowledge, this is the first report focused on the colonization process of a phyllosphere biocontrol agent and gave a clear description on the morphological shift of bacterial colony on phyllosphere. [ABSTRACT FROM AUTHOR]

The transcription factor MoAP1 has been shown previously to be required for pathogenicity in Magnaporthe oryzae via mediation of the oxidative stress response. In the serial analysis gene expression database, it was found that expression of MoYcp4, a homologue of the Saccharomyces cerevisiae flavodoxin-like protein ScYcp4, was affected by MoAP1. Transcriptional analysis demonstrated that MoYCP4 was significantly up-regulated during conidiation, appressorium formation and infection. The growth rate of a Δ Moycp4 mutant was reduced slightly, but conidial production was increased significantly (more than 10-fold), compared with the wild-type strain. Although the rate of appressorium formation was unaffected, the appressorial turgor was abnormal and the ability to infect rice and barley was reduced, resulting in decreased pathogenicity. In summary, MoYcp4, a target of MoAP1, is involved in the growth, conidiogenesis and pathogenicity of M. oryzae. Our studies provide a comprehensive analysis of flavodoxin-like proteins and will aid in the study of pathogen-related molecular mechanisms. [ABSTRACT FROM AUTHOR]

Photosynthetic bacteria ( PSB) have been extensively used in agriculture to promote plant growth and to improve crop quality. Their potential application in plant disease management, however, is largely overlooked. In this study, the PSB strain Rhodopseudomonas palustris GJ-22 was investigated for its ability to induce resistance against a plant virus while promoting plant growth. In the field, a foliar spray of GJ-22 suspension protected tobacco plants against tobacco mosaic virus ( TMV). Under axenic conditions, GJ-22 colonized the plant phyllosphere and induced resistance against TMV. Additionally, GJ-22 produced two phytohormones, indole-3-acetic acid and 5-aminolevulinic acid, which promote growth and germination in tobacco. Furthermore, GJ-22-inoculated plants elevated their immune response under subsequent TMV infection. This research may give rise to a novel biological agent with a dual function in disease management while promoting plant growth. [ABSTRACT FROM AUTHOR]