Multicellular organisms activate immunity upon recognition of pathogen-associated molecular patterns (PAMPs). Chitin is the major component of fungal cell walls, and chitin oligosaccharides act as ...PAMPs in plant and mammalian cells. Microbial pathogens deliver effector proteins to suppress PAMP-triggered host immunity and to establish infection. Here, we show that the LysM domain-containing effector protein Ecp6 of the fungal plant pathogen Cladosporium fulvum mediates virulence through perturbation of chitin-triggered host immunity. During infection, Ecp6 sequesters chitin oligosaccharides that are released from the cell walls of invading hyphae to prevent elicitation of host immunity. This may represent a common strategy of host immune suppression by fungal pathogens, because LysM effectors are widely conserved in the fungal kingdom.
The first layer of plant immunity is activated by cell surface receptor‐like kinases (RLKs) and proteins (RLPs) that detect infectious pathogens. Constitutive interaction with the SUPPRESSOR OF BIR1 ...(SOBIR1) RLK contributes to RLP stability and kinase activity. As RLK activation requires transphosphorylation with a second associated RLK, it remains elusive how RLPs initiate downstream signaling. We employed live‐cell imaging, gene silencing and coimmunoprecipitation to investigate the requirement of associated kinases for functioning and ligand‐induced subcellular trafficking of Cf RLPs that mediate immunity of tomato against Cladosporium fulvum. Our research shows that after elicitation with matching effector ligands Avr4 and Avr9, BRI1‐ASSOCIATED KINASE 1/SOMATIC EMBRYOGENESIS RECEPTOR KINASE 3 (BAK1/SERK3) associates with Cf‐4 and Cf‐9. BAK1/SERK3 is required for the effector‐triggered hypersensitive response and resistance of tomato against C. fulvum. Furthermore, Cf‐4 interacts with SOBIR1 at the plasma membrane and is recruited to late endosomes upon Avr4 trigger, also depending on BAK1/SERK3. These observations indicate that RLP‐mediated resistance and endocytosis require ligand‐induced recruitment of BAK1/SERK3, reminiscent of BAK1/SERK3 interaction and subcellular fate of the FLAGELLIN SENSING 2 (FLS2) RLK. This reveals that diverse classes of cell surface immune receptors share common requirements for initiation of resistance and endocytosis.
Vascular wilts caused by soil-borne fungal species of the Verticillium genus are devastating plant diseases. The most common species, Verticillium dahliae and Verticillium albo-atrum, have broad host ...ranges and are notoriously difficult to control. Therefore, genetic resistance is the preferred method for disease control. Only from tomato (Solarium lycopersicum) has a Verticillium resistance locus been cloned, comprising the Ve1 gene that encodes a receptor-like protein-type cell surface receptor. Due to lack of a suitable model for receptor-like protein (RLP)-mediated resistance signaling in Arabidopsis (Arabidopsis thaliana), so far relatively little is known about RLP signaling in pathogen resistance. Here, we show that Ve1 remains fully functional after interfamily transfer to Arabidopsis and that Ve1-transgenic Arabidopsis is resistant to race 1 but not to race 2 strains of V. dahliae and V. albo-atrum, nor to the Brassicaceae-specific pathogen Verticillium longisporum. Furthermore, we show that signaling components utilized by Ve1 in Arabidopsis to establish Verticillium resistance overlap with those required in tomato and include SERK3/BAK1, EDS1, and NDR1, which strongly suggests that critical components for resistance signaling are conserved. We subsequently investigated the requirement of SERK family members for Vel resistance in Arabidopsis, revealing that SERK1 is required in addition to SERK3/BAK1. Using virus-induced gene silencing, the requirement of SERK1 for Vel-mediated resistance was confirmed in tomato. Moreover, we show the requirement of SERK1 for resistance against the foliar fungal pathogen Cladosporium fulvum mediated by the RLP Cf-4. Our results demonstrate that Arabidopsis can be used as model to unravel the genetics of Vel-mediated resistance.
Observational studies are the most frequently published studies in literature. When randomized controlled trials cannot be conducted because of ethical or practical considerations, an observational ...study design is the first choice. The STROBE Statement (STrengthening the Reporting of OBservational studies in Epidemiology) was developed to provide guidance on how to adequately report observational studies.
The objectives were 1) to evaluate the quality of reporting of observational studies of otorhinolaryngologic literature using the STROBE Statement checklist, 2) to compare the quality of reporting of observational studies in the top 5 Ear, Nose, Throat (ENT) journals versus the top 5 general medical journals and 3) to formulate recommendations to improve adequate reporting of observational research in otorhinolaryngologic literature.
The top 5 general medical journals and top 5 otorhinolaryngologic journals were selected based on their ISI Web of Knowledge impact factors. On August 3rd, 2015, we performed a PubMed search using different filters to retrieve observational articles from these journals. Studies were selected from 2010 to 2014 for the general medical journals and from 2015 for the ENT journals. We assessed all STROBE items to examine how many items were reported adequately for each journal type.
The articles in the top 5 general medical journals (n = 11) reported a mean of 69.2% (95% confidence interval (CI): 65.8%-72.7%; median 70.6%), whereas the top 5 ENT journals (n = 29) reported a mean of 51.4% (95% CI: 47.7%-55.0%; median 50.0%). The two journal types reported STROBE items significantly different (p < .001).
Quality of reporting of observational studies in otorhinolaryngologic articles can considerably enhance. The quality of reporting was better in general medical journals compared to ENT journals. To improve the quality of reporting of observational studies, we recommend authors and editors to endorse and actively implement the STROBE Statement.
Cell-surface receptors form the front line of plant immunity. The leucine-rich repeat (LRR)-receptor-like kinases SOBIR1 and BAK1 are required for the functionality of the tomato LRR-receptor-like ...protein Cf-4, which detects the secreted effector Avr4 of the pathogenic fungus Fulvia fulva. Here, we show that the kinase domains of SOBIR1 and BAK1 directly phosphorylate each other and that residues Thr522 and Tyr469 of the kinase domain of Nicotiana benthamiana SOBIR1 are required for its kinase activity and for interacting with signalling partners, respectively. By knocking out multiple genes belonging to different receptor-like cytoplasmic kinase (RLCK)-VII subfamilies in N. benthamiana:Cf-4, we show that members of RLCK-VII-6, -7, and -8 differentially regulate the Avr4/Cf-4-triggered biphasic burst of reactive oxygen species. In addition, members of RLCK-VII-7 play an essential role in resistance against the oomycete pathogen Phytophthora palmivora. Our study provides molecular evidence for the specific roles of RLCKs downstream of SOBIR1/BAK1-containing immune complexes.
While youth with higher levels of depressive symptoms appear to have lower quality romantic relationships, little is known about longitudinal associations for both men and women. Therefore, this ...study used longitudinal dyadic design to examine both concurrent and longitudinal associations between depressive symptoms and positive as well as negative aspects of romantic relationship quality across two waves one- or two-years apart. The sample consisted of 149 Dutch stable heterosexual couples (149 females and 142 males participated at T
1
) in a stable romantic relationship in late adolescence with a mean age of 20.43 years old at the first wave. Actor-Partner Interdependence models were used to examine potential bidirectional associations over time between depressive symptoms and romantic relationship quality, above and beyond potential concurrent associations and stability of the constructs over time, from the perspective of both romantic partners. Results consistently indicated that men and women who reported higher levels of depressive symptoms perceived less positive aspects (intimacy and support) and more negative aspects (conflict) in their romantic relationship over time. In addition, unexpectedly, when men and women perceived more positive relationship aspects, their partners reported higher levels of depressive symptoms over time. These findings stress that depressive symptoms can interfere with the formation of high-quality romantic relationships.
Aims: Enterobacter sakazakii is an opportunistic pathogen which has been isolated at low levels from powdered infant formulas. This study was performed to demonstrate that Ent. sakazakii is not ...particularly thermotolerant, but can adapt to osmotic and dry stress.
Methods and Results: We determined the heat, osmotic and dry stress resistance of Ent. sakazakii. The D‐value at 58°C ranged from 0·39 to 0·60 min, which is comparable with that of other Enterobacteriaceae, but much lower than reported previously (Nazarowec‐White and Farber 1997, Letters in Applied Microbiology 24: 9–13). However, stationary phase Ent. sakazakii cells were found to be more resistant to osmotic and dry stress than Escherichia coli, Salmonella and other strains of Enterobacteriaceae tested. Further analysis indicated that the dry resistance is most likely linked to accumulation of trehalose in the cells.
Conclusions: The high tolerance to desiccation provides a competitive advantage for Ent. sakazakii in dry environments, as found in milk powder factories, and thereby increases the risk of postpasteurization contamination of the finished product.
Significance and Impact of the Study: Understanding of the physiology and survival strategies of Ent. sakazakii is an important step in the efforts to eliminate this bacterium from the critical food production environments.
α-tomatineis an antifungal glycoalkaloid that provides basal defense to tomato (Solanum lycopersicum). However, tomato pathogens overcome this basal defense barrier by the secretion of tomatinases ...that degrade α-tomatineinto the less fungitoxic compounds β-tomatine and tomatidine. Although pathogenic on tomato, it has been reported that the biotrophic fungus Cladosporium fulvum is unable to detoxify α-tomatine.
Here, we present a functional analysis of the glycosyl hydrolase (GH10), CfTom1, which is orthologous to fungal tomatinases.
We show that C. fulvum hydrolyzes α-tomatineinto tomatidine in vitro and during the infection of tomato, which is fully attributed to the activity of CfTom1, as shown by the heterologous expression of this enzyme in tomato. Accordingly, Δcftom1 mutants of C. fulvum are more sensitive to α-tomatineand are less virulent than the wild-type fungus on tomato. Although α-tomatineis thought to be localized in the vacuole, we show that it is also present in the apoplast, where it is hydrolyzed by CfTom1 on infection. The accumulation of tomatidine during infection appears to be toxic to tomato cells and does not suppress defense responses, as suggested previously.
Altogether, our results show that CfTom1 is responsible for the detoxification of α-tomatine by C. fulvum, and is required for full virulence of this fungus on tomato.
The plant immune system is activated by microbial patterns that are detected as nonself molecules. Such patterns are recognized by immune receptors that are cytoplasmic or localized at the plasma ...membrane. Cell surface receptors are represented by receptor-like kinases (RLKs) that frequently contain extracellular leucine-rich repeats and an intracellular kinase domain for activation of downstream signaling, as well as receptor-like proteins (RLPs) that lack this signaling domain. It is therefore hypothesized that RLKs are required for RLPs to activate downstream signaling. The RLPs Cf-4 and Ve1 of tomato (Solanum lycopersicum) mediate resistance to the fungal pathogens Cladosporium fulvum and Verticillium dahliae , respectively. Despite their importance, the mechanism by which these immune receptors mediate downstream signaling upon recognition of their matching ligand, Avr4 and Ave1, remained enigmatic. Here we show that the tomato ortholog of the Arabidopsis thaliana RLK Suppressor Of BIR1-1/Evershed (SOBIR1/EVR) and its close homolog S. lycopersicum (Sl)SOBIR1-like interact in planta with both Cf-4 and Ve1 and are required for the Cf-4– and Ve1-mediated hypersensitive response and immunity. Tomato SOBIR1/EVR interacts with most of the tested RLPs, but not with the RLKs FLS2, SERK1, SERK3a, BAK1, and CLV1. SOBIR1/EVR is required for stability of the Cf-4 and Ve1 receptors, supporting our observation that these RLPs are present in a complex with SOBIR1/EVR in planta . We show that SOBIR1/EVR is essential for RLP-mediated immunity and propose that the protein functions as a regulatory RLK of this type of cell-surface receptors.
How plants recognize pathogens and activate defense is still mysterious. Direct interaction between pathogen avirulence (Avr) proteins and plant disease resistance proteins is the exception rather ...than the rule. During infection, Cladosporium fulvum secretes Avr2 protein into the apoplast of tomato leaves and, in the presence of the extracellular leucine-rich repeat receptor-like Cf-2 protein, triggers a hypersensitive response (HR) that also requires the extracellular tomato cysteine protease Rcr3. We show here that Avr2 binds and inhibits Rcr3 and propose that the Rcr3-Avr2 complex enables the Cf-2 protein to activate an HR.
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