An inventory of invasive alien species in China

Invasive alien species (IAS) are a major global challenge requiring urgent action, and the Strategic Plan for Biodiversity (2011–2020) of the Convention on Biological Diversity (CBD) includes a target on the issue. Meeting the target requires an understanding of invasion patterns. However, national or regional analyses of invasions are limited to developed countries. We identified 488 IAS in China’s terrestrial habitats, inland waters and marine ecosystems based on available literature and field work, including 171 animals, 265 plants, 26 fungi, 3 protists, 11 procaryots, and 12 viruses. Terrestrial plants account for 51.6% of the total number of IAS, and terrestrial invertebrates (104 species) for 21.3%. Of the total numbers, 67.9% of plant IAS and 34.8% of animal IAS were introduced intentionally. All other taxa were introduced unintentionally despite very few animal and plant species that invaded naturally. In terms of habitats, 64.3% of IAS occur on farmlands, 13.9% in forests, 8.4% in marine ecosystems, 7.3% in inland waters, and 6.1% in residential areas. Half of all IAS (51.1%) originate from North and South America, 18.3% from Europe, 17.3% from Asia not including China, 7.2% from Africa, 1.8% from Oceania, and the origin of the remaining 4.3% IAS is unknown. The distribution of IAS can be divided into three zones. Most IAS are distributed in coastal provinces and the Yunnan province; provinces in Middle China have fewer IAS, and most provinces in West China have the least number of IAS. Sites where IAS were first detected are mainly distributed in the coastal region, the Yunnan Province and the Xinjiang Uyghur Autonomous Region. The number of newly emerged IAS has been increasing since 1850. The cumulative number of firstly detected IAS grew exponentially

ClpA affects the virulence of Paracidovorax citrulli on melon by regulating RepA

ClpA is a widely conserved protease in bacteria that plays a key role in virulence. To investigate its specific mechanism of action in the pathogenicity of Paracidovorax citrulli (formerly Acidovorax citrulli), we constructed a ClpA deletion mutant, ΔClpA. The ΔClpA mutant of P. citrulli displayed reduced virulence on melon seedlings, and reduced motility, swarming ability, and antioxidant capacity. On the other hand, the ClpA deletion of P. citrulli mutant reduced the resistance to elevated temperature and enhanced biofilm formation ability. Using qRT-PCR, we observed that ClpA negatively regulates the expression of the virulence-related genes virB, pilR, pilA, and fliM, while positively regulating hrpG, hrcQ, and trbC. Bacterial double hybrid and Glutathione-S-transferase pulldown (GST-pulldown) results showed that ClpA interacts directly with RepA, and negatively regulates the expression of RepA. After deletion of the RepA gene, the pathogenicity of P. citrulli was lost, biofilm formation ability was enhanced, and the expression of hrpG, pilR, and trbC was positively regulated. These results indicate that ClpA plays a key role in the regulation of several virulence traits of P. citrulli, paving the way for future studies to better elucidate the virulence mechanisms of this bacterial plant pathogen

Biofumigation by Mustard Plants as an Application for Controlling Postharvest Gray Mold in Apple Fruits

Gray mold caused by Botrytis cinerea is a critical disease that results in severe postharvest losses for the apple industry. In recent years, biological control has become an increasingly effective approach for controlling postharvest diseases in fruits. Brassica plants contain abundant natural compounds with known antimicrobial activity against numerous plant pathogens. In this study, a large-scale screening of 90 mustard cultivars was conducted to evaluate their biofumigation effects against B. cinerea. Among these, one mustard cultivar named Dilong-1, displayed the highest inhibitory effect against B. cinerea, and was able to completely inhibit mycelial growth. Further investigations showed that fumigation with Dilong-1 inhibited mycelial growth, sporulation, and spore germination of B. cinerea in vitro. In addition, fumigation using Dilong-1 showed a wide antifungal spectrum, including other fruit postharvest pathogens such as Phytophthora litchii. Furthermore, apple gray mold disease severity was significantly reduced by biofumigation using Dilong-1. Importantly, fumigation with Dilong-1 did not negatively impact final apple qualities, including weight loss, firmness, and total soluble solids. These results suggested that Dilong-1 significantly inhibited gray mold decay caused by B. cinerea without affecting the quality of apple fruits. In conclusion, biological fumigation of apple fruits with the mustard cultivar Dilong-1 is a promising eco-friendly approach for controlling apple gray mold during storage and shipment

Effect of intestinal microbiota on duck short-beak and dwarf syndrome caused by novel goose parvovirus

ABSTRACT: Short-beak and dwarf syndrome (SBDS) is caused by infection with novel goose parvovirus (NGPV), which leads to intestinal dysbiosis, developmental delay, short beak, lameness, and paralysis in ducks and is the cause of skeletal health problems. NGPV infection can cause intestinal microbial disturbances, but it is still unclear whether the intestinal microbiota affects the pathogenicity of NGPV. Here, the effects of intestinal microbiota on NGPV-induced SBDS in Cherry Valley ducks were assessed by establishing a duck model for gut microflora depletion/reestablishment through antibiotics (ABX) treatment/fecal microbiota transplanted (FMT). By measuring body weight, beak length, beak width and tarsal length, we found that SBDS clinical symptoms were alleviated in ducks treated with ABX, but not in FMT ducks. Next, we conducted a comprehensive analysis of bone metabolism, gut barrier integrity, and inflammation levels using quantitative real-time PCR (qPCR), enzyme linked immunosorbent assay (ELISA), biochemical analysis and histological analysis. The results showed that ABX treatment improved bone quality reduced bone resorption, mitigated tissue lesions, protected intestinal barrier integrity, and inhibited systemic inflammation in NGPV-infected ducks. Moreover, cecal microflora composition and short-chain fatty acids (SCFAs) production were examined by bacterial 16S rRNA sequencing and gas chromatography. The results revealed that ABX treatment mitigated the decreased abundance of Firmicutes and Bacteroidota in NGPV-infected ducks, as well as increased SCFAs production. Furthermore, ABX treatment reduced the mucosa-associated lymphoid tissue lymphoma translocation protein 1 (Malt1) and nuclear factor κB (NF-κB) expression, which are correlated with systemic inflammation in SBDS ducks. These findings suggested that intestinal microflora depletion alleviated NGPV-induced SBDS by maintaining intestinal homeostasis, inhibiting inflammatory response and alleviating bone resorption. These results provide evidence for the pivotal role of intestinal microbiota in the process of SBDS and contribute a theoretical basis for the feasibility of microecological preparation as a method to control SBDS

A Monoclonal Antibody-Based Immunochromatographic Test Strip and Its Application in the Rapid Detection of Cucumber Green Mottle Mosaic Virus

Two specific monoclonal antibodies (mAbs) were screened, and an immunochromatographic strip (ICS) test for rapid and specific detection of cucumber green mottle mosaic virus (CGMMV) was developed. The coat protein of CGMMV was heterologously expressed as an immunogen, and specific capture mAb 2C9 and the detection mAb 4D4 were screened by an uncompetitive immunoassay. The test and control lines on the nitrocellulose membrane were coated with the purified 2C9 and a goat anti-mouse IgG, respectively, and a nanogold probe combined with 4D4 was applied to the conjugate pad. Using these mAbs, a rapid and sensitive ICS was developed. Within the sandwich mode of 2C9–CGMMV–4D4, the test line showed a corresponding positive relationship with CGMMV in infected samples. The ICS test had a detection limit of 1:5000 (w/v) for CGMMV in samples and was specific for CGMMV, with no observed cross-reaction with TMV or CMV

Table_1_OxyR contributes to virulence of Acidovorax citrulli by regulating anti-oxidative stress and expression of flagellin FliC and type IV pili PilA.docx

In many bacteria, OxyR acts as a transcriptional regulator that facilitates infection via degrading hydrogen peroxide (H2O2) generated by the host defense response. Previous studies showed that OxyR also plays an important role in regulating biofilm formation, cell motility, pili relate-genes expression, and surface polysaccharide production. However, the role of OxyR has not been determined in Acidovorax citrulli strain xjl12. In the current study, the qRT-PCR and western blot assays revealed that the expression level of oxyR was significantly induced by H2O2. The oxyR deletion mutant of A. citrulli was significantly impaired bacterial tolerance to oxidative stress and reduced catalase (CAT) activity. In addition, oxyR mutant resulted in reduced swimming motility, twitching motility, biofilm formation, virulence, and bacterial growth in planta by significantly affecting flagellin and type IV pili-related gene (fliC and pilA) expression. The qRT-PCR assays and western blot revealed that OxyR positively regulated the expression of fliC and pilA. Furthermore, bacterial one-hybrid assay demonstrated that OxyR directly affected pilA and fliC promoter. Through bacterial two-hybrid assay, it was found that OxyR can directly interact with PilA and FliC. These results suggest that OxyR plays a major role in the regulating of a variety of virulence traits, and provide a foundation for future research on the global effects of OxyR in A. citrulli.</p

Proteomic Analysis Reveals Novel Extracellular Virulence-Associated Proteins and Functions Regulated by the Diffusible Signal Factor (DSF) in <i>Xanthomonas oryzae</i> pv. <i>oryzicola</i>

Quorum sensing (QS) in <i>Xanthomonas oryzae</i> pv. <i>oryzicola</i> (Xoc), the causal agent of bacterial leaf streak, is mediated by the diffusible signal factor (DSF). DSF-mediating QS has been shown to control virulence and a set of virulence-related functions; however, the expression profiles and functions of extracellular proteins controlled by DSF signal remain largely unclear. In the present study, 33 DSF-regulated extracellular proteins, whose functions include small-protein mediating QS, oxidative adaptation, macromolecule metabolism, cell structure, biosynthesis of small molecules, intermediary metabolism, cellular process, protein catabolism, and hypothetical function, were identified by proteomics in Xoc. Of these, 15 protein encoding genes were in-frame deleted, and 4 of them, including three genes encoding type II secretion system (T2SS)-dependent proteins and one gene encoding an Ax21 (activator of XA21-mediated immunity)-like protein (a novel small-protein type QS signal) were determined to be required for full virulence in Xoc. The contributions of these four genes to important virulence-associated functions, including bacterial colonization, extracellular polysaccharide, cell motility, biofilm formation, and antioxidative ability, are presented. To our knowledge, our analysis is the first complete list of DSF-regulated extracellular proteins and functions in a <i>Xanthomonas</i> species. Our results show that DSF-type QS played critical roles in regulation of T2SS and Ax21-mediating QS, which sheds light on the role of DSF signaling in <i>Xanthomonas</i>

Proteomic Analysis Reveals Novel Extracellular Virulence-Associated Proteins and Functions Regulated by the Diffusible Signal Factor (DSF) in <i>Xanthomonas oryzae</i> pv. <i>oryzicola</i>

Quorum sensing (QS) in <i>Xanthomonas oryzae</i> pv. <i>oryzicola</i> (Xoc), the causal agent of bacterial leaf streak, is mediated by the diffusible signal factor (DSF). DSF-mediating QS has been shown to control virulence and a set of virulence-related functions; however, the expression profiles and functions of extracellular proteins controlled by DSF signal remain largely unclear. In the present study, 33 DSF-regulated extracellular proteins, whose functions include small-protein mediating QS, oxidative adaptation, macromolecule metabolism, cell structure, biosynthesis of small molecules, intermediary metabolism, cellular process, protein catabolism, and hypothetical function, were identified by proteomics in Xoc. Of these, 15 protein encoding genes were in-frame deleted, and 4 of them, including three genes encoding type II secretion system (T2SS)-dependent proteins and one gene encoding an Ax21 (activator of XA21-mediated immunity)-like protein (a novel small-protein type QS signal) were determined to be required for full virulence in Xoc. The contributions of these four genes to important virulence-associated functions, including bacterial colonization, extracellular polysaccharide, cell motility, biofilm formation, and antioxidative ability, are presented. To our knowledge, our analysis is the first complete list of DSF-regulated extracellular proteins and functions in a <i>Xanthomonas</i> species. Our results show that DSF-type QS played critical roles in regulation of T2SS and Ax21-mediating QS, which sheds light on the role of DSF signaling in <i>Xanthomonas</i>