Polyamine-containing natural products have been isolated from a wide range of terrestrial and marine organisms. Most of them exhibit remarkable and diverse activities with potential applications in human health and agriculture.

Cowpea (Vigna unguiculata L.) is a legume consumed as a high-quality plant protein source in many parts of the world. In August 2023, it was observed that a plant disease affected cowpea growth in Yiyang (28.34°N, 112.55°E), China. The average disease incidence was 10%, resulting in 8.5% economic losses in approximately 3,000 m². The symptoms initially appeared as brown lesions near the stem-soil interface and the lesions were colonized by white mycelia. As the disease progressed, the disease symptoms included constriction and brown staining at the base of the stem, covered with a small amount of white mycelia. Eventually, the entire plants withered and collapsed and many sclerotia were scattered on the ground around the diseased stem. Twenty samples (10 sclerotia and 10 diseased tissue fragments) were collected from symptomatic plants for causal agent isolation. Samples were disinfected with 70% ethanol for 30 s, 5% NaClO for 1 min, rinsed three times with sterile water, dried and placed on potato dextrose agar (PDA) plates at 28℃ in the dark. In total, 20 isolates were obtained by the hyphal tip method (Terrones et al. 2022) and showed a consistent phenotype of white cottony mycelia on PDA with an growth rate of 12.9 to 21.3 mm/day (n = 20). Sclerotia formed at five to eight days post inoculation, were initially whitish, turning beige and eventually dark brown. The diameter of mature sclerotia ranged from 0.89 to 2.13 mm (mean = 1.64±0.29 mm; n =50). For pathogen identification, ITS1/ITS4 (White et al. 1990) and EF1-983F/EF1-2218R (Rehner and Buckley 2005) primers were used to amplify the internal transcribed spacer regions (ITS) and translation elongation factor-1 alpha gene (TEF-1α), respectively. The sequences of all 20 isolates showed 99% to 100% similarity with Agroathelia rolfsii sequences from GenBank by BLAST analysis. The sequences of two representative strains, ID1 and ID4, were deposited in GenBank. The ITS sequences of ID1 (OR689482) and ID4 (OR689481) were ＞99% similar to A. rolfsii strain QJ7 (593/596 bp; MZ750983) and A. rolfsii strain Kale078 (565/568 bp; MN872304), respectively. Also, TEF-1α sequences of ID1 (OR713735) and ID4 (OR713736) were ＞99% similar to the sequences of A. rolfsii strain HS-Sr (1073/1073 bp; OL416131) and A. rolfsii strain MSB1-2 (1070/1075 bp; MN702790), respectively. Phylogenetic analysis based on ITS and TEF1-α sequences indicated that ID1 and ID4 clustered into the A. rolfsii clade. Based on morphology and sequence analyses, the isolates ID1 and ID4 were identified as A. rolfsii (anamorph Sclerotium rolfsii). Pathogenicity tests were conducted three times on healthy 30-day-old cowpea seedlings. Five plants were inoculated with 6-day-old mycelial discs (6 mm) of ID1 or ID4 at the base of the seedlings (n = 30) while four plants were inoculated with a sterile PDA disc as a control (n = 12). All seedlings were cultivated in a greenhouse with a temperature of 26°C to 28°C and relative humidity 60% to 80% with a 14/10 h light/dark photoperiod. Eight days later, all the fungal inoculated seedlings showed symptoms including brown necrosis and collapse of the stems, and eventual withering of the seedlings. Control plants remained asymptomatic. The causal pathogens were reisolated in PDA plates and identified by ITS sequence analysis, completing Koch's postulates. To our knowledge, this is the first report of A. rolfsii causing southern blight on cowpea in China. Early accurate diagnosis will help farmers to adopt suitable practices to control disease outbreaks and reduce losses.

Summary: Edeines, a group of cationic antimicrobial peptides produced by the soil bacterium Brevibacillus, have broad biological effects, such as antimicrobial, anticancer and immunosuppressive activities. However, the yield of edeines in wild‐type (WT) Brevibacillus is extremely low, and chemical synthesis of edeines is a time‐consuming process. Genetic engineering has proven to be an effective approach to produce antibiotics with high yield. In this study, the ede ine b iosynthetic g ene c luster ( ede BGC), which is involved in edeine production, was identified and characterized in Brevibacillus brevis X23. To improve edeine production in B. brevis X23, the ede BGC promoter was replaced with six different promoters, P _mwp , P _spc , P _xylA , P _shuttle‐09 , P _grac or P ₄₃ , through double‐crossover homologous recombination. The new promoters significantly increased the expression of the ede BGC as well as edeine production by 2.9 ± 0.4 to 20.5 ± 1.2‐fold and 3.6 ± 0.1to 8.7 ± 0.7‐fold respectively. The highest yield of edeines (83.6 mg l ⁻¹ ) was obtained in B. brevis X23 with the P _mwp promoter. This study provides a practical approach for producing high yields of edeines in B . brevis .

Brevibacillus brevis is one of the most common biocontrol strains with broad applications in the prevention and control of plant diseases and insect pests. In order to deepen our understanding of B. brevis genomes, describe their characteristics comprehensively, and mine secondary metabolites, we retrieved the genomic sequences of nine B. brevis strains that had been assembled into complete genomes from the NCBI database. These genomic sequences were analyzed using phylogenetic analysis software, pan-genome analysis software, and secondary metabolite mining software. Results revealed that the genome size of B. brevis strains ranged from 6.16 to 6.73 Mb, with GC content ranging from 47.0% to 54.0%. Phylogenetic analysis classified the nine B. brevis strains into three branches. The analyses of ANI and dDDH showed that B. brevis NEB573 had the potential to become a new species of Brevibacillus and needed further research in the future. The pan-genome analysis identified 10032 gene families, including 3257 core gene families, 3112 accessory gene families, and 3663 unique gene families. In addition, 123 secondary metabolite biosynthetic gene clusters of 20 classes were identified in the genomes of nine B. brevis strains. The major types of biosynthetic gene clusters were non-ribosomal peptide synthase (NRPS) and transAT polyketide synthase (transAT-PKS). Furthermore, a large number of untapped secondary metabolites were identified in B. brevis. In summary, this study elucidated the pan-genome characteristics of the biocontrol bacterium B. brevis and identified its secondary metabolites, providing valuable insights for its further development and utilization.

Pepper(Capsicum annuum L.) is the vegetable with the largest production area China (Zou and Zou 2021). In the summer of 2020 and 2021, disease symptoms were observed in C. annuum L. cv. bola in a 1...

Edeines are a group of non-ribosomal antibacterial peptides produced by Brevibacillus brevis. Due to the significant antibacterial properties of edeines, increasing edeine yield is of great interest in biomedical research. Herein, we identified that EdeB, a member of the ParB protein family, significantly improved edeine production in B. brevis. First, overexpression of edeB in B. brevis X23 increased edeine production by 92.27%. Second, in vitro bacteriostasis experiment showed that edeB-deletion mutant exhibited less antibacterial activity. Third, RT-qPCR assay demonstrated that the expression of edeA, edeQ, and edeK, which are key components of the edeine biosynthesis pathway, in edeB-deletion mutant X23(ΔedeB) was significantly lower than that in wild-type B. brevis strain X23. Finally, electrophoretic mobility shift assay (EMSA) showed that EdeB directly bound to the promoter region of the edeine biosynthetic gene cluster (ede BGC), suggesting that EdeB improves edeine production through interaction with ede BGC in B. brevis.