Search

Xenorhabdus, known for its symbiotic relationship with Entomopathogenic nematodes (EPNs), belongs to the Enterobacteriaceae family. This dual-host symbiotic nematode exhibits pathogenic traits, rendering it a promising biocontrol agent against insects. Our prior investigations revealed that Xenorhabdus stockiae HN_xs01, isolated in our laboratory, demonstrates exceptional potential in halting bacterial growth and displaying anti-tumor activity. Subsequently, we separated and purified the supernatant of the HN_xs01 strain and obtained a new compound with significant inhibitory activity on tumor cells, which we named XNAE. Through LC-MS analysis, the mass-to-nucleus ratio of XNAE was determined to be 254.24. Our findings indicated that XNAE exerts a time- and dose-dependent inhibition on B16 and HeLa cells. After 24 h, its IC50 for B16 and HeLa cells was 30.178 µg/mL and 33.015 µg/mL, respectively. Electron microscopy revealed conspicuous damage to subcellular structures, notably mitochondria and the cytoskeleton, resulting in a notable reduction in cell numbers among treated tumor cells. Interestingly, while XNAE exerted a more pronounced inhibitory effect on B16 cells compared to HeLa cells, it showed no discernible impact on HUVEC cells. Treatment of B16 cells with XNAE induced early apoptosis and led to cell cycle arrest in the G2 phase, as evidenced by flow cytometry analysis. The impressive capability of X. stockiae HN_xs01 in synthesizing bioactive secondary metabolites promises to significantly expand the reservoir of natural products. Further exploration to identify the bioactivity of these compounds holds the potential to shed light on their roles in bacteria-host interaction. Overall, these outcomes underscore the promising potential of XNAE as a bioactive compound for tumor treatment. [ABSTRACT FROM AUTHOR]

Type synthesis of parallel mechanism is regarded as the theoretical basis and source for the original innovation design of mechanical devices and robots. A new method for type synthesis of the fully-decoupled two-rotational and one-translational (2R1T) parallel mechanisms with three degrees of freedom is proposed in this paper. Based on the actuation wrench screw theory, the mathematical model mapping the input and output velocity vector space of the fully-decoupled 2R1T parallel mechanism is established. The actuation wrench screws and the actuated twist screws of the corresponding branches are derived according to the mathematic model. The forms of the unactuated screws are determined in terms of the reciprocal product theory. Structural synthesis of the branch chains is realized. Then type synthesis of parallel mechanisms is completed as well and lots of novel mechanisms are obtained. Finally, a 2RUPU-PU parallel mechanism synthesized is taken as an example to analyze its mobility and kinematics. Results show that the mechanism has two-rotational and one-translational degrees of freedom and its Jacobian matrix is a diagonal matrix, i.e., it has the fully-decoupled kinematic characteristics. Therefore, the method proposed is correct and effective to synthesize the fully-decoupled 2R1T parallel mechanisms. [ABSTRACT FROM AUTHOR]

Xenorhabdus can produce a large number of secondary metabolites with insecticidal, bacteriostatic, and antitumor activities. Efficient gene editing tools will undoubtedly facilitate the functional genomics research and bioprospecting in Xenorhabdus. In this study, BlastP analysis using the amino acid sequences of Redαβ or RecET recombinases as queries resulted in the identification of an operon (XBJ1_operon 0213) containing RecET-like recombinases encoding genes from the genome of Xenorhabdus bovienii strain SS-2004. Three proteins encoded by this operon was indispensable for full activity of recombineering, namely XBJ1-1173 (RecE-like protein), XBJ1-1172 (RecT-like protein), and XBJ1-1171 (single-strand annealing protein). Using this newly developed recombineering system, a gene cluster responsible for biosynthesis of a novel secondary metabolite (Min16) was identified from X. stockiae HN_xs01 strain. Min16 which exhibited antibacterial and cytotoxic activities was determined to be a cyclopeptide composed of Acyl-Phe-Thr-Phe-Pro-Pro-Leu-Val by using high-resolution mass spectrometry and nuclear magnetic resonance analysis, and was designated as changshamycin. This host-specific recombineering system was proven to be effective for gene editing in Xenorhabdus, allowing for efficient discovery of novel natural products with attractive bioactivities. Key points: • Screening and identification of efficient gene editing tools from Xenorhabdus • Optimization of the Xenorhabdus electroporation parameters • Discovery of a novel cyclopeptide compound with multiple biological activities [ABSTRACT FROM AUTHOR]

Saccharina latissima (sugar kelp) is one of the most widely cultivated brown marine macroalgae species in the North Atlantic and the eastern North Pacific Oceans. To meet the expanding demands of the sugar kelp mariculture industry, selecting and breeding sugar kelp that is best suited to offshore farm environments is becoming necessary. To that end, a multi-year, multi-institutional breeding program was established by the U.S. Department of Energy's (DOE) Advanced Research Projects Agency-Energy (ARPA-E) Macroalgae Research Inspiring Novel Energy Resources (MARINER) program. Hybrid sporophytes were generated using 203 unique gametophyte cultures derived from wild-collected Saccharina spp. for two seasons of farm trials (2019–2020 and 2020–2021). The wild sporophytes were collected from 10 different locations within the Gulf of Maine (USA) region, including both sugar kelp (Saccharina latissima) and the skinny kelp species (Saccharina angustissima). We harvested 232 common farm plots during these two seasons with available data. We found that farmed kelp plots with skinny kelp as parents had an average increased yield over the mean (wet weight 2.48 ± 0.90 kg m−1 and dry weight 0.32 ± 0.10 kg m−1) in both growing seasons. We also found that blade length positively correlated with biomass in skinny kelp x sugar kelp crosses or pure sugar kelp crosses. The skinny x sugar progenies had significantly longer and narrower blades than the pure sugar kelp progenies in both seasons. Overall, these findings suggest that sugar x skinny kelp crosses provide improved yield compared to pure sugar kelp crosses. [ABSTRACT FROM AUTHOR]

The overall objective of this study is to present an assessment of embryonic sporophyte development directly "seeded" on growing substrates using the proprietary binder AtSea and three formulations of calcium alginate. We conducted two independent experiments under controlled conditions in a laboratory setup. First, we compared the effect of salinity (0 ppt, 29 ppt, and 35 ppt) on the performance of the calcium alginate formulations. Second, we assessed the effect of direct seeding with binders on the development of sporophytes of four different size classes (i.e., 83.7, 183.1, 345.2, and 522.0 μm in length). Our results show that salinity affects the performance of calcium alginate with 0 ppt media allowing the formation of a thicker hydrogel than that formulated with 29 and 35 ppt. Results also show that AtSea retained more sporophytes than any formulations of calcium alginate. Although effective when cultures were maintained in complete stillness (i.e., no water motion), we detected 70–80% detachment when aeration was added. We also observed what appeared to be delayed sporophyte development compared with sporophytes growing as free floaters. [ABSTRACT FROM AUTHOR]

Key message: The recessive Hessian fly resistance gene h4 and flanking SNP markers were located to a 642 kb region in chromosome 1A of the wheat cultivar 'Java.' Hessian fly (HF), Mayetiola destructor, is one of the most destructive insect pests in wheat worldwide. The wheat cultivar 'Java' was reported to carry a recessive gene (h4) for HF resistance; however, its chromosome location has not been determined. To map the HF resistance gene in Java, two populations of recombinant inbred lines (RILs) were developed from 'Bobwhite' × Java and 'Overley' × Java, respectively, and were phenotyped for responses to infestation of HF Great Plains biotype. Analysis of phenotypic data from the F1 and the RIL populations confirmed that one recessive gene conditioned HF resistance in Java. Two linkage maps were constructed using single-nucleotide polymorphism (SNP) markers generated by genotyping-by-sequencing (GBS). The h4 gene was mapped to the distal end of the short arm of chromosome 1A, which explained 60.4 to 70.5% of the phenotypic variation for HF resistance in the two populations. The GBS-SNPs in the h4 candidate interval were converted into Kompetitive Allele-Specific Polymerase Chain Reaction (KASP) markers to eliminate the missing data points in GBS-SNPs. Using the revised maps with KASP markers, h4 was further located to a 642 kb interval (6,635,984–7,277,935 bp). The two flanking KASP markers, KASP3299 and KASP1871, as well as four other closely linked KASP markers, may be useful for pyramiding h4 with other HF resistance genes in breeding. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been shown to increase plant stress tolerance. However, the molecular mechanisms underlying the effects of Si in alleviating drought stress in winter wheat are unknown. The aim of this study was to investigate the effects of Si on photosynthetic pigments, antioxidant contents, and transcription of several genes involved in the antioxidant defense pathway in drought-stressed wheat plants. Si application resulted in higher leaf chlorophyll content, and lower lipid peroxidation levels and HO contents in wheat flag leaves compared with untreated plants. In addition, Si increased the contents of ascorbate (ASC), reduced glutathione (GSH), and the total phenolic and total flavonoid contents in wheat flag leaves. Quantitative real-time PCR was used to analyze gene expression patterns for three antioxidant enzyme genes, four ASC-GSH cycle genes, and five flavonoid biosynthesis pathway genes. Si application increased the expression of these genes in drought-stressed wheat compared with the −Si treatments. Elevated levels of gene expression and low malondialdehyde and HO contents indicate that Si plays a pivotal role in the coordinated transcriptional regulation of multiple antioxidant defenses in response to drought. Our work also suggests that Si may be important in the metabolic or physiological activities for growth and development of winter wheat. [ABSTRACT FROM AUTHOR]

A Correction to this paper has been published: https://doi.org/10.1007/s10811-020-02345-4 [ABSTRACT FROM AUTHOR]