Low prevalence of secondary endosymbionts in aphids sampled from rapeseed crops in Germany.

Peach-potato aphids, Myzus persicae Sulzer (Hemiptera:Aphididae), and cabbage aphids, Brevicoryne brassicae Linnaeus (Hemiptera:Aphididae), are herbivorous insects of significant agricultural importance. Aphids can harbour a range of non-essential (facultative) endosymbiotic bacteria that confer multiple costs and benefits to the host aphid. A key endosymbiont-derived phenotype is protection against parasitoid wasps, and this protective phenotype has been associated with several defensive enodsymbionts. In recent years greater emphasis has been placed on developing alternative pest management strategies, including the increased use of natural enemies such as parasitoids wasps. For the success of aphid control strategies to be estimated the presence of defensive endosymbionts that can potentially disrupt the success of biocontrol agents needs to be determined in natural aphid populations. Here, we sampled aphids and mummies (parasitised aphids) from an important rapeseed production region in Germany and used multiplex PCR assays to characterise the endosymbiont communities. We found that aphids rarely harboured facultative endosymbionts, with 3.6% of M. persicae and 0% of B. brassicae populations forming facultative endosymbiont associations. This is comparable with endosymbiont prevalence described for M. persicae populations surveyed in Australia, Europe, Chile, and USA where endosymbiont infection frequencies range form 0-2%, but is in contrast with observations from China where M. persicae populations have more abundant and diverse endosymbiotic communities (endosymbionts present in over 50% of aphid populations).

Supplementation of lactobacillus-fermented rapeseed meal in broiler diet reduces Campylobacter jejuni cecal colonization and limits the l-tryptophan and l-histidine biosynthesis pathways.

BACKGROUND: Campylobacter jejuni (C. jejuni), a widely distributed global foodborne pathogen, primarily linked with contaminated chicken meat, poses a significant health risk. Reducing the abundance of this pathogen in poultry meat is challenging but essential. This study assessed the impact of Lactobacillus-fermented rapeseed meal (LFRM) on broilers exposed to C. jejuni-contaminated litter, evaluating growth performance, Campylobacter levels, and metagenomic profile. RESULTS: By day 35, the litter contamination successfully colonized broilers with Campylobacter spp., particularly C. jejuni. In the grower phase, LFRM improved (P < 0.05) body weight and daily weight gain, resulting in a 9.2% better feed conversion ratio during the pre-challenge period (the period before artificial infection; days 13-20). The LFRM also reduced the C. jejuni concentration in the ceca (P < 0.05), without altering alpha and beta diversity. However, metagenomic data analysis revealed LFRM targeted a reduction in the abundance of C. jejuni biosynthetic pathways of l-tryptophan and l-histidine and gene families associated with transcription and virulence factors while also possibly leading to selected stress-induced resistance mechanisms. CONCLUSION: The study demonstrated that LFRM inclusion improved growth and decreased cecal Campylobacter spp. concentration and the relative abundance of pivotal C. jejuni genes. Performance benefits likely resulted from LFRM metabolites. At the molecular level, LFRM may have reduced C. jejuni colonization, likely by decreasing the abundance of energy transduction and l-histidine and l-tryptophan biosynthesis genes otherwise required for bacterial survival and increased virulence. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Fermented rape pollen powder can alleviate benign prostatic hyperplasia in rats by reducing hormone content and changing gut microbiota.

Benign prostatic hyperplasia (BPH) can cause urethral compression, bladder stone formation, and renal function damage, which may endanger the life of patients. Therefore, we aimed to develop plant-based preparations for BPH treatment with no side effects. In this study, the Lactiplantibacillus plantarum 322Hp, Lactobacillus acidophilus 322Ha, and Limosilactobacillus reuteri 322Hr were used to ferment rape pollen. The fermented rape pollen was subsequently converted into fermented rape pollen powder (FRPP) through vacuum freeze-drying technology. After fermenting and drying, the bioactive substances and antioxidant capacity of FRPP were significantly higher than those of unfermented rapeseed pollen, and FRPP had a longer storage duration, which can be stored for over one year. To investigate the therapeutic effect of FRPP on BPH, a BPH rat model was established by hypodermic injection of testosterone propionate. The BPH rats were treated differently, with the model group receiving normal saline, the positive control group receiving finasteride, and the low, medium, and high dose FRPP group receiving FRPP at doses of 0.14 g/kg/d, 0.28 g/kg/d, and 0.56 g/kg/d, respectively. The results indicate that medium dose FRPP reduced the levels of hormone such as testosterone, dihydrotestosterone, and oestradiol in rats with BPH by about 32%, thus bringing the prostate tissue of BPH rats closer to normal. More importantly, medium dose FRPP treatment had a significant effect on the composition of gut microbiota in rats with BPH, increasing the levels of beneficial genera (such as Coprococcus and Jeotgalicoccus), and decreasing the levels of harmful pathogens (such as Turicibacter and Clostridiaceae_Clostridium) in the gut. This study showed that medium dose FRPP reduced the hormone level and regulated the unbalanced gut microbiota in BPH rats, thereby alleviating BPH.

Selection pressure on the rhizosphere microbiome can alter nitrogen use efficiency and seed yield in Brassica rapa.

Microbial experimental systems provide a platform to observe how networks of groups emerge to impact plant development. We applied selection pressure for microbiome enhancement of Brassica rapa biomass to examine adaptive bacterial group dynamics under soil nitrogen limitation. In the 9th and final generation of the experiment, selection pressure enhanced B. rapa seed yield and nitrogen use efficiency compared to our control treatment, with no effect between the random selection and control treatments. Aboveground biomass increased for both the high biomass selection and random selection plants. Soil bacterial diversity declined under high B. rapa biomass selection, suggesting a possible ecological filtering mechanism to remove bacterial taxa. Distinct sub-groups of interactions emerged among bacterial phyla such as Proteobacteria and Bacteroidetes in response to selection. Extended Local Similarity Analysis and NetShift indicated greater connectivity of the bacterial community, with more edges, shorter path lengths, and altered modularity through the course of selection for enhanced plant biomass. In contrast, bacterial communities under random selection and no selection showed less complex interaction profiles of bacterial taxa. These results suggest that group-level bacterial interactions could be modified to collectively shift microbiome functions impacting the growth of the host plant under soil nitrogen limitation.

Spatiotemporal Heterogeneity and Intragenus Variability in Rhizobacterial Associations with Brassica rapa Growth.

Microbial communities in the rhizosphere are distinct from those in soils and are influenced by stochastic and deterministic processes during plant development. These communities contain bacteria capable of promoting growth in host plants through various strategies. While some interactions are characterized in mechanistic detail using model systems, others can be inferred from culture-independent methods, such as 16S amplicon sequencing, using machine learning methods that account for this compositional data type. To characterize assembly processes and identify community members associated with plant growth amid the spatiotemporal variability of the rhizosphere, we grew Brassica rapa in a greenhouse time series with amended and reduced microbial treatments. Inoculation with a native soil community increased plant leaf area throughout the time series by up to 28%. Despite identifying spatially and temporally variable amplicon sequence variants (ASVs) in both treatments, inoculated communities were more highly connected and assembled more deterministically overall. Using a generalized linear modeling approach controlling for spatial variability, we identified 43 unique ASVs that were positively or negatively associated with leaf area, biomass, or growth rates across treatments and time stages. ASVs of the genus Flavobacterium dominated rhizosphere communities and showed some of the strongest positive and negative correlations with plant growth. Members of this genus, and growth-associated ASVs more broadly, exhibited variable connectivity in networks independent of growth association (positive or negative). These findings suggest host-rhizobacterial interactions vary temporally at narrow taxonomic scales and present a framework for identifying rhizobacteria that may work independently or in concert to improve agricultural yields. IMPORTANCE The rhizosphere, the zone of soil surrounding plant roots, is a hot spot for microbial activity, hosting bacteria capable of promoting plant growth in ways like increasing nutrient availability or fighting plant pathogens. This microbial system is highly diverse and most bacteria are unculturable, so to identify specific bacteria associated with plant growth, we used culture-independent community DNA sequencing combined with machine learning techniques. We identified 43 specific bacterial sequences associated with the growth of the plant Brassica rapa in different soil microbial treatments and at different stages of plant development. Most associations between bacterial abundances and plant growth were positive, although similar bacterial groups sometimes had different effects on growth. Why this happens will require more research, but overall, this study provides a way to identify native bacteria from plant roots that might be isolated and applied to boost agricultural yields.

Persistence of Escherichia coli in the microbiomes of red Romaine lettuce (Lactuca sativa cv. 'Outredgeous') and mizuna mustard (Brassica rapa var. japonica) - does seed sanitization matter?

BACKGROUND: Seed sanitization via chemical processes removes/reduces microbes from the external surfaces of the seed and thereby could have an impact on the plants' health or productivity. To determine the impact of seed sanitization on the plants' microbiome and pathogen persistence, sanitized and unsanitized seeds from two leafy green crops, red Romaine lettuce (Lactuca sativa cv. 'Outredgeous') and mizuna mustard (Brassica rapa var. japonica) were exposed to Escherichia coli and grown in controlled environment growth chambers simulating environmental conditions aboard the International Space Station. Plants were harvested at four intervals from 7 days post-germination to maturity. The bacterial communities of leaf and root were investigated using the 16S rRNA sequencing while quantitative polymerase chain reaction (qPCR) and heterotrophic plate counts were used to reveal the persistence of E. coli. RESULT: E. coli was detectable for longer periods of time in plants from sanitized versus unsanitized seeds and was identified in root tissue more frequently than in leaf tissue. 16S rRNA sequencing showed dynamic changes in the abundance of members of the phylum Proteobacteria, Firmicutes, and Bacteroidetes in leaf and root samples of both leafy crops. We observed minimal changes in the microbial diversity of lettuce or mizuna leaf tissue with time or between sanitized and unsanitized seeds. Beta-diversity showed that time had more of an influence on all samples versus the E. coli treatment. CONCLUSION: Our results indicated that the seed surface sanitization, a current requirement for sending seeds to space, could influence the microbiome. Insight into the changes in the crop microbiomes could lead to healthier plants and safer food supplementation.

Effect of capsaicinoids in hot pepper powder on microbial community and free sugar during kimchi fermentation.

Effect of capsaicinoids in hot pepper powder (HP) contains various chemical compounds, including capsaicin and dihydrocapsaicin, which are the main ingredients of the spicy taste. To evaluate the effect of HP on the microbial community in kimchi fermentation, kimchi [kimchi-HP, kimchi-HPE and kimchi-HPER made by adding HP, HP alcohol extract (HPE) and HPE residues (HPER)] was fermented at 4°C for 28 days. The pH and titratable acidity of the samples and the number of bacteria changed with fermentation time. Kimchi-HPER had significantly higher total viable and lactic acid bacteria (LAB) than other samples after 28 days of fermentation. The capsaicinoids content did not differ before and after fermentation, whereas the major free sugar content decreased, and the mannitol content increased. The principal component analysis (PCA) biplots showed similar patterns between kimchi-HP and -HPE. It was confirmed that Leuconostoc and Weissella were related to the initial fermentation, and Lactobacillus was involved in late fermentation. Kimchi-HP and kimchi-HPE increased the ratio of Lactobacillus sakei and decreased that of Leuconostoc mesenteroides compared to kimchi-HPER. Overall, these results revealed that capsaicinoids contained in HP affected Lactobacillus proliferation and mannitol increase during kimchi fermentation.

Epigenetic Modulating Chemicals Significantly Affect the Virulence and Genetic Characteristics of the Bacterial Plant Pathogen Xanthomonas campestris pv. campestris.

Epigenetics is the study of heritable alterations in phenotypes that are not caused by changes in DNA sequence. In the present study, we characterized the genetic and phenotypic alterations of the bacterial plant pathogen Xanthomonas campestris pv. campestris (Xcc) under different treatments with several epigenetic modulating chemicals. The use of DNA demethylating chemicals unambiguously caused a durable decrease in Xcc bacterial virulence, even after its reisolation from infected plants. The first-time use of chemicals to modify the activity of sirtuins also showed some noticeable results in terms of increasing bacterial virulence, but this effect was not typically stable. Changes in treated strains were also confirmed by using methylation sensitive amplification (MSAP), but with respect to registered SNPs induction, it was necessary to consider their contribution to the observed polymorphism. The molecular basis of the altered virulence was deciphered by using dualRNA-seq analysis of treated Xcc strains infecting Brassica rapa plants. The results of the present study should promote more intensive research in the generally understudied field of bacterial epigenetics, where artificially induced modification by epigenetic modulating chemicals can significantly increase the diversity of bacterial properties and potentially contribute to the further development of the fields, such as bacterial ecology and adaptation.

An efficient direct screening system for microorganisms that activate plant immune responses based on plant-microbe interactions using cultured plant cells.

Microorganisms that activate plant immune responses have attracted considerable attention as potential biocontrol agents in agriculture because they could reduce agrochemical use. However, conventional methods to screen for such microorganisms using whole plants and pathogens are generally laborious and time consuming. Here, we describe a general strategy using cultured plant cells to identify microorganisms that activate plant defense responses based on plant-microbe interactions. Microbial cells were incubated with tobacco BY-2 cells, followed by treatment with cryptogein, a proteinaceous elicitor of tobacco immune responses secreted by an oomycete. Cryptogein-induced production of reactive oxygen species (ROS) in BY-2 cells served as a marker to evaluate the potential of microorganisms to activate plant defense responses. Twenty-nine bacterial strains isolated from the interior of Brassica rapa var. perviridis plants were screened, and 8 strains that enhanced cryptogein-induced ROS production in BY-2 cells were selected. Following application of these strains to the root tip of Arabidopsis seedlings, two strains, Delftia sp. BR1R-2 and Arthrobacter sp. BR2S-6, were found to induce whole-plant resistance to bacterial pathogens (Pseudomonas syringae pv. tomato DC3000 and Pectobacterium carotovora subsp. carotovora NBRC 14082). Pathogen-induced expression of plant defense-related genes (PR-1, PR-5, and PDF1.2) was enhanced by the pretreatment with strain BR1R-2. This cell-cell interaction-based platform is readily applicable to large-scale screening for microorganisms that enhance plant defense responses under various environmental conditions.

MicroRNA319a regulates plant resistance to Sclerotinia stem rot.

MicroRNA319a (miR319a) controls cell division arrest in plant leaves by inhibiting the expression of TCP (TEOSINTE BRANCHED 1/CYCLOIDEA/PCF) family genes. However, it is unclear whether miR319a influences infection by necrotrophic pathogens and host susceptibility. In this study, we revealed that miR319a affects plant resistance to stem rot disease caused by Sclerotinia sclerotiorum. In Brassica rapa plants infected with S. sclerotiorum, miR319a levels increased while the expression levels of several BraTCP genes significantly decreased compared with those of uninfected plants. Overexpression of BraMIR319a in B. rapa increased the susceptibility of the plants to S. sclerotiorum and aggravated stem rot disease, whereas overexpression of BraTCP4-1 promoted plant resistance. RNA sequencing data revealed a potential relationship between miR319a and pathogen-related WRKY genes. Chromatin immunoprecipitation, electrophoretic mobility shift, and reporter transaction assays showed that BraTCP4-1 could bind to the promoters of WRKY75, WRKY70, and WRKY33 and directly activate these pathogen-related genes. Moreover, the expression levels of WRKY75, WRKY70, and WRKY33 in plants overexpressing BraMIR319a decreased significantly, whereas those of plants overexpressing BraTCP4-1 increased significantly, relative to the wild type. These results suggest that miR319a and its target gene BraTCP4 control stem rot resistance through pathways of WRKY genes.

The transcriptional response to salicylic acid plays a role in Fusarium yellows resistance in Brassica rapa L.

KEY MESSAGE: Fusarium yellows resistant and susceptible lines in Brassica rapa showed different salicylic acid responses; the resistant line showed a similar response to previous reports, but the susceptible line differed. Fusarium yellows caused by Fusarium oxysporum f. sp. conglutinans (Foc) is an important disease. Previous studies showed that genes related to salicylic acid (SA) response were more highly induced following Foc infection in Brassica rapa Fusarium yellows resistant lines than susceptible lines. However, SA-induced genes have not been identified at the whole genome level and it was unclear whether they were up-regulated by Foc inoculation. Transcriptome analysis with and without SA treatment in the B. rapa Fusarium yellows susceptible line 'Misugi' and the resistant line 'Nanane' was performed to obtain insights into the relationship between SA sensitivity/response and Fusarium yellows resistance. 'Nanane's up-regulated genes were related to SA response and down-regulated genes were related to jasmonic acid (JA) or ethylene (ET) response, but differentially expressed genes in 'Misugi' were not. This result suggests that Fusarium yellows resistant and susceptible lines have a different SA response and that an antagonistic transcription between SA and JA/ET responses was found only in a Fusarium yellows resistant line. SA-responsive genes were induced by Foc inoculation in Fusarium yellows resistant (RJKB-T23) and susceptible lines (RJKB-T24). By contrast, 39 SA-induced genes specific to RJKB-T23 might function in the defense response to Foc. In this study, SA-induced genes were identified at the whole genome level, and the possibility, the defense response to Foc observed in a resistant line could be mediated by SA-induced genes, is suggested. These results will be useful for future research concerning the SA importance in Foc or other diseases resistance in B. rapa.

Application of colorimetric indicators to predict the fermentation stage of kimchi.

Cabbage kimchi, a popular side dish in Korean cuisine, produces several fermentation by-products (FBPs). Kimchi is praised for its flavor, taste, and texture when suitably fermented at 0.7% to 0.9% total acidity, or a pH of approximately 4.1. Beyond this acidity level, the quality of the product decreases, negatively impacting consumers' purchase preferences. Therefore, the current study seeks to develop an optimally fermented (OptF) kimchi indicator that can be inserted into product packaging to evaluate its utility at 4 and 10 °C. A gradual change in the total color difference (ΔE) was observed during the kimchi fermentation stage, and the highest ΔE values were observed at 4 (34.87) and 10 °C (37.99), after 9 weeks. Moreover, the color-change response function value F(Xc) was more linear at 4 and 10 °C (0.981 and 0.984, respectively) compared to the ΔE over time, during kimchi fermentation. Coefficients of determination for F(Xc)-carbon dioxide (0.983), F(Xc)-pH (0.979), and F(Xc)-titratable acidity (0.974) were sufficient to meet the optimal polynomial regression model, while that for F(Xc)-lactic acid bacteria (0.881) was not. Standardized residuals of predicted data indicated that 95% of the residuals were in the range of -2.0 to 2.0. The regression analysis further suggested that the OptF kimchi indicator could be used as a kimchi fermentation indicator. PRACTICAL APPLICATION: Cabbage kimchi, a traditional Korean fermented food, produces several fermentation by-products. After the optimal fermenting stage, the sensory evaluation of cabbage kimchi and consumers' purchase preference decreases. This study describes an optimally fermented kimchi indicator and its utility at 4 and 10 °C. Our results demonstrate the ability of this indicator to predict the freshness and fermentation stage of kimchi without the need for sensory evaluation. This method could help increase the purchase preference for commercial kimchi.

Lactobacillus plantarum Shinshu N-07 isolated from fermented Brassica rapa L. attenuates visceral fat accumulation induced by high-fat diet in mice.

Lactobacillus plantarum Shinshu N-07 (N07) and Lactobacillus curvatus #4G2 (#4G2) were isolated from fermented Brassica rapa L. and selected as promising probiotics with anti-adiposity activities based on in vitro assays. The anti-adiposity effects of these two strains were investigated using a diet-induced obesity animal model. Epididymal adipose tissue weight and adipocyte area were significantly lower and serum triglycerides and glucose tended to be lower in mice fed the high-fat diet supplemented with N07 compared with those fed the unsupplemented high-fat diet. Strain N07 suppressed hepatic steatosis, with accompanying downregulation of lipogenic genes in the liver. Expression of inflammatory cytokines and macrophage infiltration markers tended to be suppressed by N07 supplementation. Upregulation of uncoupling protein-1 in epididymal adipose tissue by N07 suggested that the transformation of white adipose tissue to brown might have been induced. Intestinal microbiota analysis revealed that a decrease in abundance of family S24-7 (phylum Bacteroidetes) following ingestion of the high-fat diet was partly recovered by supplementation with N07. Changes in those parameters were not observed in mice fed the high-fat diet supplemented with strain #4G2, suggesting strain specificities. Thus, N07 is a potential probiotic strain that could be used to develop functional foods that attenuate visceral fat accumulation after an appropriate human intervention trial.

Expression and Role of Biosynthetic, Transporter, Receptor, and Responsive Genes for Auxin Signaling during Clubroot Disease Development.

Auxins play a pivotal role in clubroot development caused by the obligate biotroph Plasmodiophora brassicae. In this study, we investigated the pattern of expression of 23 genes related to auxin biosynthesis, reception, and transport in Chinese cabbage (Brassica rapa) after inoculation with P. brassicae. The predicted proteins identified, based on the 23 selected auxin-related genes, were from protein kinase, receptor kinase, auxin responsive, auxin efflux carrier, transcriptional regulator, and the auxin-repressed protein family. These proteins differed in amino acids residue, molecular weights, isoelectric points, chromosomal location, and subcellular localization. Leaf and root tissues showed dynamic and organ-specific variation in expression of auxin-related genes. The BrGH3.3 gene, involved in auxin signaling, exhibited 84.4-fold increase in expression in root tissues compared to leaf tissues as an average of all samples. This gene accounted for 4.8-, 2.6-, and 5.1-fold higher expression at 3, 14, and 28 days post inoculation (dpi) in the inoculated root tissues compared to mock-treated roots. BrNIT1, an auxin signaling gene, and BrPIN1, an auxin transporter, were remarkably induced during both cortex infection at 14 dpi and gall formation at 28 dpi. BrDCK1, an auxin receptor, was upregulated during cortex infection at 14 dpi. The BrLAX1 gene, associated with root hair development, was induced at 1 dpi in infected roots, indicating its importance in primary infection. More interestingly, a significantly higher expression of BrARP1, an auxin-repressed gene, at both the primary and secondary phases of infection indicated a dynamic response of the host plant towards its resistance against P. brassicae. The results of this study improve our current understanding of the role of auxin-related genes in clubroot disease development.

Saccharibacillus brassicae sp. nov., an endophytic bacterium isolated from kimchi cabbage (Brassica rapa subsp. pekinensis) seeds.

Strain ATSA2T was isolated from surface-sterilized kimchi cabbage (Brassica rapa subsp. pekinensis) seeds and represents a novel bacterium based on the polyphasic taxonomic approach. A phylogenetic analysis based on 16S rRNA gene sequences showed that strain ATSA2T formed a lineage within genus Saccharibacillus and was most closely to Saccharibacillus deserti WLG055T (98.1%) and Saccharibacillus qing-shengii H6T (97.9%). The whole-genome of ATSA2T comprised a 5,619,468 bp of circular chromosome with 58.4% G + C content. The DNA-DNA relatedness values between strain ATSA2T and its closely related type strains S. deserti WLJ055 and S. qingshengii H6T were 26.0% and 24.0%, respectively. Multiple gene clusters associated with plant growth promotion activities (stress response, nitrogen and phosphorus metabolism, and auxin biosynthesis) were annotated in the genome. Strain ATSA2T was Gram-positive, endospore-forming, facultatively anaerobic, and rod-shaped It grew at 15-37°C (optimum 25°C), pH 6.0-10.0 (optimum pH 8.0), and in the presence of 0-5% (w/v) NaCl (optimum 1%). The major cellular fatty acids (> 10%) of strain ATSA2T were anteiso-C15:0 and C16:0. MK-7 was the major isoprenoid quinone. The major polar lipids present were diphosphatidylglycerol, phosphatidylglycerol, and three unknown glycolipids. Based on its phylogenetic, genomic, phenotypic, and chemotaxo-nomic features, strain ATSA2T is proposed to represent a novel species of genus Saccharibacillus, for which the name is Saccharibacillus brassicae sp. nov. The type strain is ATSA2T (KCTC 43072T = CCTCC AB 2019223T).

[Difference of the microbial community structure in the rhizosphere of soybean and oilseed rape based on high-throughput pyrosequencing analysis.] / åŸºäºŽé«˜é€šé‡æµ‹åºåˆ†æžå¤§è±†å’Œæ²¹èœæ ¹é™ å¾®ç”Ÿç‰©ç¾¤è½ç»“æž„çš„å·®å¼‚.

Clubroot, caused by the soil-borne obligate pathogen Plasmodiophora brassicae, is one of the most severe disease in cruciferous crops. Previous studies showed that when oilseed rape was planted after soybean (namely soybean-oilseed rotation), the incidence and severity of clubroot of oilseed rape could be significantly reduced, compared with that with oilseed rape-oilseed rape conti-nuous cropping. Therefore, the soybean-oilseed rape rotation is a good way to suppress clubroot of oilseed rape. In this study, we compared the rhizosphere microbiome of soybean and oilseed rape rhizosphere soil collected from the field by 16S rRNA (for identification of prokaryotes) and the internal transcribed spacer (ITS) (for identification of fungi) sequencing. The results showed that both soybean and oilseed rape rhizosphere soils had Proteobacteria, Bacteroidetes, Acidobacteria, Actinobacteria, Ascomycota, Zygomycota, Basidiomycota and Chytridiomycota. Many microbial genera (e.g., Flavobacterium, Sphingomonas, Bacillus, Streptomyces, Pseudomonas, Trichoderma and Coniothyrium) with activities of biological control and plant growth promotion were more abundant in soybean rhizosphere soil than in the oilseed rape rhizosphere soil. The abundance of plant pathogenic bacteria and fungi was higher in the oilseed rape rhizosphere soil than in the soybean rhizosphere soil. Moreover, the soybean rhizosphere soil was enriched with Rhizobium, Bradyrhizobium (both for nitrogen fixation), and arbuscular mycorrhizal fungus (Glomus). These results indicated that soybean rhizosphere soil could promote the growth and proliferation of beneficial microorga-nisms, but inhibit that of plant pathogens. Our results provide evidence for explanation of the effectiveness of soybean-oilseed rape rotation to control clubroot of oilseed rape and provide potential bio-control resources for clubroot prevention.

A Gain-of-Function Screen Reveals Redundant ERF Transcription Factors Providing Opportunities for Resistance Breeding Toward the Vascular Fungal Pathogen Verticillium longisporum.

Verticillium longisporum is a vascular fungal pathogen leading to severe crop loss, particular in oilseed rape. Transcription factors (TF) are highly suited for genetic engineering of pathogen-resistant crops, as they control sets of functionally associated genes. Applying the AtTORF-Ex (Arabidopsis thaliana transcription factor open reading frame expression) collection, a simple and robust screen of TF-overexpressing plants was established displaying reduced fungal colonization. Distinct members of the large ethylene response factor (ERF) family, namely ERF96 and the six highly related subgroup IXb members ERF102 to ERF107, were identified. Whereas overexpression of these ERF significantly reduces fungal propagation, single loss-of-function approaches did not reveal altered susceptibility. Hence, this gain-of-function approach is particularly suited to identify redundant family members. Expression analyses disclosed distinct ERF gene activation patterns in roots and leaves, suggesting functional differences. Transcriptome studies performed on chemically induced ERF106 expression revealed an enrichment of genes involved in the biosynthesis of antimicrobial indole glucosinolates (IG), such as CYP81F2 (CYTOCHROME P450-MONOOXYGENASE 81F2), which is directly regulated by IXb-ERF via two GCC-like cis-elements. The impact of IG in restricting fungal propagation was further supported as the cyp81f2 mutant displayed significantly enhanced susceptibility. Taken together, this proof-of-concept approach provides a novel strategy to identify candidate TF that are valuable genetic resources for engineering or breeding pathogen-resistant crop plants.

AhlX, an N-acylhomoserine Lactonase with Unique Properties.

N-Acylhomoserine lactonase degrades the lactone ring of N-acylhomoserine lactones (AHLs) and has been widely suggested as a promising candidate for use in bacterial disease control. While a number of AHL lactonases have been characterized, none of them has been developed as a commercially available enzymatic product for in vitro AHL quenching due to their low stability. In this study, a highly stable AHL lactonase (AhlX) was identified and isolated from the marine bacterium Salinicola salaria MCCC1A01339. AhlX is encoded by a 768-bp gene and has a predicted molecular mass of 29 kDa. The enzyme retained approximately 97% activity after incubating at 25 °C for 12 days and ~100% activity after incubating at 60 °C for 2 h. Furthermore, AhlX exhibited a high salt tolerance, retaining approximately 60% of its activity observed in the presence of 25% NaCl. In addition, an AhlX powder made by an industrial spray-drying process attenuated Erwinia carotovora infection. These results suggest that AhlX has great potential for use as an in vitro preventive and therapeutic agent for bacterial diseases.

Characterization of Microbiota that Influence Immunomodulatory Effects of Fermented Brassica rapa L.

Lactic acid bacteria (LAB) exert beneficial health effects by regulating immune responses. Brassica rapa L., known as Nozawana, is commonly consumed as a lactic acid-fermented food called nozawana-zuke. Few studies have investigated changes in the bacterial community and cytokine production activities during the fermentation of B. rapa L. In order to obtain more detail information, we herein conducted a study on fresh B. rapa L. fermented for 28 d. An amplicon analysis of the 16S rRNA gene revealed that Lactobacillales predominated during fermentation, and the microbiota became less diverse on day 7 or later. Fermented B. rapa L. promoted the production of interferon (IFN)-γ and interleukin (IL)-10 by mouse spleen cells more than non-fermented vegetables. Lactobacillus curvatus was the predominant species during fermentation, followed by L. plantarum and L. brevis. L. sakei was occasionally detected. A correlation analysis showed that IFN-γ concentrations positively correlated with the numbers of L. curvatus and L. plantarum, while those of IL-10 correlated with the numbers of L. sakei in addition to these 2 species. Significantly higher levels of IFN-γ and IL-10 were induced by fermented B. rapa L. when isolated Lactobacillus strains were added as starter cultures. These results suggest that the Lactobacillus species present in fermented B. rapa L. are beneficial for manufacturing vegetables with immunomodulatory effects.

Agrobacterium-mediated vacuum infiltration and floral dip transformation of rapid-cycling Brassica rapa.

BACKGROUND: Rapid-cycling Brassica rapa (RCBr), also known as Wisconsin Fast Plants, are small robust plants with a short lifecycle that are widely used in biology teaching. RCBr have been used for decades but there are no published reports of RCBr genetic transformation. Agrobacterium-mediated vacuum infiltration has been used to transform pakchoi (Brassica rapa ssp. chinensis) and may be suitable for RCBr transformation. The floral dip transformation method, an improved version of vacuum infiltration, could make the procedure easier. RESULTS: Based on previous findings from Arabidopsis and pakchoi, plants of three different ages were inoculated with Agrobacterium. Kanamycin selection was suboptimal with RCBr; a GFP screen was used to identify candidate transformants. RCBr floral bud dissection showed that only buds with a diameter less than 1 mm carried unsealed carpels, a key point of successful floral dip transformation. Plants across a wide range of inflorescence maturities but containing these immature buds were successfully transformed, at an overall rate of 0.1% (one per 1000 T1 seeds). Transformation was successful using either vacuum infiltration or the floral dip method, as confirmed by PCR and Southern blot. CONCLUSION: A genetic transformation system for RCBr was established in this study. This will promote development of new biology teaching tools as well as basic biology research on Brassica rapa.