Han Xu

Applications of animal manure and treated wastewater could enrich antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the plant microbiome. However, the mechanistic studies of the transmission of ARB and ARGs from the environment to plant endophytic bacteria were few. Herein, a genetically engineered fluorescent Escherichia coli harboring a conjugative RP4 plasmid that carries three ARGs was used to trace its spread into Arabidopsis thaliana interior in a tetracycline-amended hydroponic system in the absence or presence of a simulated soil bacterial community. Confocal microscope observation demonstrated that E. coli was internalized into plant tissues and the carried RP4 plasmid was transferred into plant endophytic bacteria. More importantly, we observed that soil bacteria inhibited the internalization of E. coli but substantially promoted RP4 plasmid spread into the plant microbiome. The altered RP4-carrying bacterial community composition in the plant microbiome and the increased core-shared RP4-carrying bacteria number between plant interior and exterior in the presence of soil bacteria collectively confirmed that soil bacteria, especially Proteobacteria, might capture RP4 from E. coli and then translocate into plant microbiome, resulting in the increased RP4 plasmid spread in the plant endophytes. Overall, our findings provided important insights into the dissemination of ARB and ARGs from the environment to the plant microbiome.

Phloretin, a dihydrochalcone structural flavonoid compound, possesses antioxidant activity. In this study, we conducted studies to explore the function of phloretin on high palmitic acid-induced oxidative stress in human umbilical vein endothelial cells and investigated the potential mechanism using ribonucleic acid sequencing (RNA-Seq). Our findings reveal that phloretin significantly decreased the levels of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA), increased superoxide dismutase (SOD) and glutathione peroxidase-1 (Gpx-1) activity, and restored the loss of mitochondrial membrane potential (MMP). Next, whole transcriptome analysis was performed using RNA-Seq The results indicated more than 3000 differentially expressed genes (DEGs). Gene Ontology analysis revealed that the DEGs were categorized functionally, mainly by the biological processes, cell metabolism, and cellular response to chemical stimulus. The Kyoto Encyclopedia of Genes and Genomes indicated that they were mainly enriched in cAMP, apoptosis, and cytoskeletal regulation signaling pathways. Furthermore, on the basis of the results of RNA-Seq and Western blotting, our study verified that phloretin upregulated the expression of p-Nrf2 and HO-1 by promoting the phosphorylation of AMPK at Thr172 through activation of liver kinase B1. In conclusion, phloretin attenuates PA-induced oxidative stress in HUVECs via the AMPK/Nrf2 antioxidative pathway.

Porcine circovirus type 2 (PCV2) is the essential infectious agent responsible for causing porcine circovirus-associated diseases in pigs. To date, eleven RNAs and five viral proteins of PCV2 have been detected. Here, we identified a novel viral gene within the PCV2 genome, termed ORF5, that exists at both the transcriptional and translational level during productive infection of PCV2 in porcine alveolar macrophages 3D4/2 (PAMs). Northern blot analysis was used to demonstrate that the ORF5 gene measures 180 bp in length and overlaps completely with ORF1 when read in the same direction. Site-directed mutagenesis was used to show that the ORF5 protein is not essential for PCV2 replication. To investigate the biological functions of the novel protein, we constructed a recombinant eukaryotic expression plasmid capable of expressing PCV2 ORF5. The results show that the GFP-tagged PCV2 ORF5 protein localizes to the endoplasmic reticulum (ER), is degraded via the proteasome, inhibits PAM growth and prolongs the S-phase of the cell cycle. Further studies show that the GFP-tagged PCV2 ORF5 protein induces ER stress and activates NF-κB, which was further confirmed by a significant upregulation in IL-6, IL-8 and COX-2 expression. In addition, five cellular proteins (GPNMB, CYP1A1, YWHAB, ZNF511 and SRSF3) were found to interact with ORF5 via yeast two-hybrid assay. These findings provide novel information on the identification and functional analysis of the PCV2 ORF5 protein and are likely to be of benefit in elucidating the molecular mechanisms of PCV2 pathogenicity. However, additional experiments are needed to validate the expression and function of the ORF5 protein during PCV2 infection in vitro before any definitive conclusion can be drawn.