The Sl TPL3–Sl WUS module regulates multi-locule formation in tomato by modulating auxin and gibberellin levels in the shoot apical meristem

Malformed fruits depreciate a plant’s market value.In tomato(Solanum lycopersicum),fruit malformation is associated with the multi-locule trait,which involves genes regulating shoot apical meristem(SAM) development.The expression pattern of TOPLESS3(SITPL3) throughout SAM development prompted us to investigate its functional significance via RNA interference(RNAi) and clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease 9(Cas9)-mediated gene editing.Lower SITPL3 t...     

The Prevalence of Multidrug Resistance Is Higher among Bovine than Human Salmonella enterica Serotype Newport,Typhimurium, and 4,5,12:i:? Isolates in the United States but Differs by Serotype and Geographic Region

Salmonella represents an important zoonotic pathogen worldwide, but the transmission dynamics between humans and animals as well as within animal populations are incompletely understood. We characterized Salmonella isolates from cattle and humans in two geographic regions of the United States, the Pacific Northwest and the Northeast, using three common subtyping methods (pulsed-field gel electrophoresis [PFGE], multilocus variable number of tandem repeat analysis [MLVA], and multilocus sequence typing [MLST]). In addition, we analyzed the distribution of antimicrobial resistance among human and cattle Salmonella isolates from the two study areas and characterized Salmonella persistence on individual dairy farms. For both Salmonella enterica subsp. enterica serotypes Newport and Typhimurium, we found multidrug resistance to be significantly associated with bovine origin of isolates, with the odds of multidrug resistance for Newport isolates from cattle approximately 18 times higher than for Newport isolates from humans. Isolates from the Northwest were significantly more likely to be multidrug resistant than those from the Northeast, and susceptible and resistant isolates appeared to represent distinct Salmonella subtypes. We detected evidence for strain diversification during Salmonella persistence on farms, which included changes in antimicrobial resistance as well as genetic changes manifested in PFGE and MLVA pattern shifts. While discriminatory power was serotype dependent, the combination of PFGE data with either MLVA or resistance typing data consistently allowed for improved subtype discrimination. Our results are consistent with the idea that cattle are an important reservoir of multidrug-resistant Salmonella infections in humans. In addition, the study provides evidence for the value of including antimicrobial resistance data in epidemiological investigations and highlights the benefits and potential problems of combining subtyping methods.Salmonella is an important human and animal pathogen worldwide. In the United States, Salmonella causes an estimated 1.4 million human cases, 15,000 hospitalizations, and more than 400 deaths each year (44, 75). Human infections can be acquired through contact with animals or humans shedding Salmonella or through contaminated environments, but the majority of human infections are food-borne, and a large number of human outbreaks have been linked to foods of animal origin (20). Beef represents one well-recognized source of human infection (71). In addition, a number of human cases have been linked to dairy products or cattle contact, for instance at state fairs or on dairy farms (for example, see references 25, 35, and 61).Salmonella enterica subsp. enterica serotypes Typhimurium and Newport are commonly isolated from human cases, including those linked to cattle (20, 61). In 2006, Salmonella serotypes Typhimurium and Newport were isolated from 17 and 8% of reported human salmonellosis cases in the United States, respectively, making them the first and third most common human disease-associated serotypes in the United States (15). S. enterica serotype 4,5,12:i:− is both genetically and antigenically closely related to Salmonella serotype Typhimurium, of which it represents a monophasic variant (62). Salmonella enterica serotype 4,5,12:i:− is characterized by a deletion of flagellar genes fliA and fliB, which prevents expression of the phase 2 flagellar antigen (60). In the United States, the prevalence of Salmonella serotype 4,5,12:i:− has increased considerably over the past 10 years, and in 2006, Salmonella serotype 4,5,12:i:− represented the sixth most commonly isolated serotype from humans in the United States (15, 60).Salmonella serotype Newport represents two distinct clonal groups or lineages—one predominantly associated with isolates from cattle (i.e., Newport lineage A) and one associated with isolates from birds (i.e., Newport lineage B) (1, 33). Members of both lineages cause human infections (1, 33). The two Newport lineages can be clearly distinguished by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE), and some correlation between genetic lineage and antimicrobial resistance profile seems to exist (1, 33). In general, Newport lineage B isolates are pansusceptible or resistant to only a few antimicrobial drugs. In contrast, lineage A is strongly associated with multidrug resistance and includes a Newport subtype commonly referred to as Newport MDR-AmpC (1, 33).The prevalence of antimicrobial resistance among Salmonella serotype Newport and Typhimurium isolates has increased worldwide during the last 2 decades, predominantly as a result of emerging multidrug-resistant (MDR) strains (14, 52, 65). During the 1990s, Salmonella serotype Typhimurium phage type DT104 with pentaresistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT) increased considerably in prevalence around the world, and some isolates acquired resistance to additional antimicrobial agents, including trimethoprim or ciprofloxacin (52). MDR Salmonella serotype Typhimurium DT104 has been isolated from a wide variety of host species and caused numerous large human outbreaks around the world (65). Salmonella serotype Newport MDR-AmpC, characterized by resistance to ACSSuT and carrying a plasmid encoding resistance to amoxicillin-clavulanic acid, cefoxitin, ceftiofur, and cephalothin emerged in the United States during the late 1990s, where it quickly became widespread among humans and cattle, leading to several large human outbreaks (14).Whether antimicrobial drug use in animals facilitates the emergence of MDR human pathogens is still subject to debate. Some studies report a temporal association between the introduction of new antimicrobial agents in veterinary medicine and the emergence of antimicrobial resistance (for instance, see references 22 and 58), but questions regarding the underlying evolutionary mechanisms, the origin and distribution of naturally occurring resistance genes, and the role of antimicrobial usage among humans remain (for example, see references 2 and 66 for reviews on this topic). Moreover, some studies report a higher prevalence of antimicrobial resistance among Salmonella isolates from farm animals than humans. Gebreyes et al. (26), for instance, found a higher prevalence of antimicrobial resistance among Salmonella isolates from pigs than humans, but potential effects attributable to differences in serotype distribution are difficult to assess in this study. In recent years, risk factors for MDR have received considerable attention. Infections with MDR Salmonella strains can lead to treatment failures, may be of longer duration, and may result in more severe clinical disease. Hence, such infections lead more often to hospitalization or death than infections with susceptible Salmonella strains, but serotype or subtype differences between resistant and susceptible Salmonella strains complicate the interpretation of clinical data (34, 41, 68).Subtyping methods allow characterization of Salmonella isolates and include phenotypic methods (e.g., serotyping or phage typing) as well as molecular subtyping methods, such as pulsed-field gel electrophoresis (PFGE), ribotyping, multilocus variable number of tandem repeat analysis (MLVA), and multilocus sequence typing (MLST) (5). PFGE is widely used and robust, and rigorous standardization allows comparison between laboratories (5). However, the method is time-intensive and laborious, requires careful standardization and analysis, does not allow phylogenetic inference, and can in rare cases be affected by endogenous nucleases or DNA methylation (for a review of this topic, see reference 5). MLVA and MLST are rapid, allow for easy data exchange between laboratories, and provide some phylogenetic information (5). MLVA is highly discriminatory but subject to rapid diversification and therefore most appropriate for the analysis of closely related isolates. While MLST lacks discriminatory power within Salmonella serotypes, it is highly reproducible and allows for phylogenetic analysis of more distantly related isolates (1, 5, 33). PFGE and MLST can be performed regardless of serotype, but MLVA protocols are serotype specific and have so far only been validated for a limited number of Salmonella serotypes. Moreover, MLVA can be complicated by inaccurate sizing of DNA fragments, and the degree of reliability can be considerably influenced by nucleotide composition and fragment length (5). Overall, these subtyping methods differ considerably in discriminatory power and sometimes yield conflicting results, and the most appropriate subtyping method or combination thereof strongly depends on serotype and chosen application (19, 56, 72, 76). Other genetic or phenotypic characteristics, such as antimicrobial resistance patterns or the presence of specific plasmids, have also been used successfully for subtyping in outbreak investigations and other epidemiological studies and can provide valuable additional information (7, 8, 40, 63, 64).Here we describe the distribution and subtype diversity of Salmonella serotypes Newport, 4,5,12:i:−, and Typhimurium among cattle and humans in two geographic regions of the United States, and we assess common risk factors for multidrug resistance. In addition, we utilize three Salmonella subtyping methods (PFGE, MLVA, and MLST), analyze their usefulness for characterizing isolates representing three common human-associated Salmonella serotypes, and compare the combined discriminatory power of PFGE and MLVA to that of PFGE and antimicrobial resistance patterns.