Summary
The rhizobium‐legume symbiosis is the best‐understood plant–microbe association. The high degree of specificity observed in this relationship is supported by a complex exchange of signals ...between the two components of the symbiosis. Findings reported in last years indicate that multiple molecular mechanisms, such as the production of a particular set of nodulation factors at a very specific concentration or a suitable arsenal of effectors secreted through the type III secretion system, have been adjusted during evolution to ensure and optimize the recognition of specific rhizobial strains by its legume host. Qualitative or quantitative changes in the production of these symbiotic molecular determinants are detrimental for nodulation with its natural host but, in some cases, can also result beneficial for the rhizobium since it extends the nodulation host‐range to other legumes. Potential repercussion of the extension in the nodulation host‐range of rhizobia is discussed.
SUMMARY
Bacterial fruit blotch, caused by Acidovorax citrulli, is a serious disease of melon and watermelon. The strains of the pathogen belong to two major genetic groups: group I strains are ...strongly associated with melon, while group II strains are more aggressive on watermelon. A. citrulli secretes many protein effectors to the host cell via the type III secretion system. Here we characterized AopW1, an effector that shares similarity to the actin cytoskeleton‐disrupting effector HopW1 of Pseudomonas syringae and with effectors from other plant‐pathogenic bacterial species. AopW1 has a highly variable region (HVR) within amino acid positions 147 to 192, showing 14 amino acid differences between group I and II variants. We show that group I AopW1 is more toxic to yeast and Nicotiana benthamiana cells than group II AopW1, having stronger actin filament disruption activity, and increased ability to induce cell death and reduce callose deposition. We further demonstrated the importance of some amino acid positions within the HVR for AopW1 cytotoxicity. Cellular analyses revealed that AopW1 also localizes to the endoplasmic reticulum, chloroplasts, and plant endosomes. We also show that overexpression of the endosome‐associated protein EHD1 attenuates AopW1‐induced cell death and increases defense responses. Finally, we show that sequence variation in AopW1 plays a significant role in the adaptation of group I and II strains to their preferred hosts, melon and watermelon, respectively. This study provides new insights into the HopW1 family of bacterial effectors and provides first evidence on the involvement of EHD1 in response to biotic stress.
Significance Statement
The bacterium Acidovorax citrulli is a serious pathogen of cucurbit crops. Here we characterize AopW1, a type III‐secreted effector of the pathogen that interacts with the host actin cytoskeleton. We show that genetic variation in AopW1 within the A. citrulli population is associated with cytotoxic ability and bacterial adaptation to different hosts within cucurbit plants. We also provide first evidence on the involvement of the endosome protein EHD1 in response to biotic stress.
The present study analyzes the relationship between three distal antecedents-financial literacy, confidence in retirement, and economic well-being-and financial planning for retirement evaluated at ...two different times. We used longitudinal data with repeated measures of financial planning for retirement obtained from a sample (N = 269) of active Spanish workers aged 45-62 years. The results confirm that self-perceived financial knowledge, confidence in retirement, and economic well-being are associated with financial planning for retirement at three and six months. The stability of financial planning for retirement over time was a relevant finding in the present research, even though different measures have been employed in the two waves and financial planning decreases slightly at three months. While the first step of planning, at three months, has predictive power over the second, at six months, there are possible moderators in the relationship between financial planning for retirement at time 1 and time 2, which were not explored. The implications of the results both for financial education and Policy-makers are discussed. Future lines of research can explore these relationships including objective measures of income, as wealth accumulation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Summary
The cucurbit pathogenic bacterium Acidovorax citrulli requires a functional type III secretion system (T3SS) for pathogenicity. In this bacterium, as with Xanthomonas and Ralstonia spp., an ...AraC‐type transcriptional regulator, HrpX, regulates expression of genes encoding T3SS components and type III‐secreted effectors (T3Es). The annotation of a sequenced A. citrulli strain revealed 11 T3E genes. Assuming that this could be an underestimation, we aimed to uncover the T3E arsenal of the A. citrulli model strain, M6. Thorough sequence analysis revealed 51 M6 genes whose products are similar to known T3Es. Furthermore, we combined machine learning and transcriptomics to identify novel T3Es. The machine‐learning approach ranked all A. citrulli M6 genes according to their propensity to encode T3Es. RNA‐Seq revealed differential gene expression between wild‐type M6 and a mutant defective in HrpX: 159 and 28 genes showed significantly reduced and increased expression in the mutant relative to wild‐type M6, respectively. Data combined from these approaches led to the identification of seven novel T3E candidates that were further validated using a T3SS‐dependent translocation assay. These T3E genes encode hypothetical proteins that seem to be restricted to plant pathogenic Acidovorax species. Transient expression in Nicotiana benthamiana revealed that two of these T3Es localize to the cell nucleus and one interacts with the endoplasmic reticulum. This study places A. citrulli among the ‘richest’ bacterial pathogens in terms of T3E cargo. It also revealed novel T3Es that appear to be involved in the pathoadaptive evolution of plant pathogenic Acidovorax species.
Summary
Sinorhizobium fredii HH103 RifR, a broad‐host‐range rhizobial strain, forms ineffective nodules with Lotus japonicus but induces nitrogen‐fixing nodules in Lotus burttii roots that are ...infected by intercellular entry. Here we show that HH103 RifR nolR or nodD2 mutants gain the ability to induce infection thread formation and to form nitrogen‐fixing nodules in L. japonicus Gifu. Microscopy studies showed that the mode of infection of L. burttii roots by the nodD2 and nolR mutants switched from intercellular entry to infection threads (ITs). In the presence of the isoflavone genistein, both mutants overproduced Nod‐factors. Transcriptomic analyses showed that, in the presence of Lotus japonicus Gifu root exudates, genes related to Nod factors production were overexpressed in both mutants in comparison to HH103 RifR. Complementation of the nodD2 and nolR mutants provoked a decrease in Nod‐factor production, the incapacity to form nitrogen‐fixing nodules with L. japonicus Gifu and restored the intercellular way of infection in L. burttii. Thus, the capacity of S. fredii HH103 RifR nodD2 and nolR mutants to infect L. burttii and L. japonicus Gifu by ITs and fix nitrogen L. japonicus Gifu might be correlated with Nod‐factor overproduction, although other bacterial symbiotic signals could also be involved.
Extracellular vesicles are produced by many pathogenic microorganisms and have varied functions that include secretion and release of microbial factors, which contribute to virulence. Very little is ...known about vesicle production by Gram-positive bacteria, as well as their biogenesis and release mechanisms. In this work, we demonstrate the active production of vesicles by Streptococcus pneumoniae from the plasma membrane, rather than being a product from cell lysis. We biochemically characterized them by proteomics and fatty acid analysis, showing that these vesicles and the plasma membrane resemble in essential aspects, but have some differences: vesicles are more enriched in lipoproteins and short-chain fatty acids. We also demonstrate that these vesicles act as carriers of surface proteins and virulence factors. They are also highly immunoreactive against human sera and induce immune responses that protect against infection. Overall, this work provides insights into the biology of this important Gram-positive human pathogen and the role of extracellular vesicles in clinical applications.
Pneumococcus is one of the leading causes of bacterial pneumonia worldwide in children and the elderly, being responsible for high morbidity and mortality rates in developing countries. The augment of pneumococcal disease in developed countries has raised major public health concern, since the difficulties to treat these infections due to increasing antibiotic resistance. Vaccination is still the best way to combat pneumococcal infections. One of the mechanisms that bacterial pathogens use to combat the defense responses of invaded hosts is the production and release of extracellular vesicles derived from the outer surface. Little is known about this phenomenon in Gram-positives. We show that pneumococcus produces membrane-derived vesicles particularly enriched in lipoproteins. We also show the utility of pneumococcal vesicles as a new type of vaccine, as they induce protection in immunized mice against infection with a virulent strain. This work will contribute to understand the role of these structures in important biological processes such as host-pathogen interactions and prevention of human disease.
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•Pneumococcus produces membrane vesicles that are released to the milieu.•Proteomics show that they are more enriched in lipoproteins than the cell membrane.•Membrane vesicles induce protection against pneumococcal infection in mice.
Oceanic islands are characterized by conditions that favour diversification into endemic lineages that can be very different from their mainland counterparts. This can be the result of fast ...phenotypic divergence due to drift or the result of slower adaptation to local conditions. This uniqueness can obscure their evolutionary history. Here we used morphological, stable isotope, genetic and genomic data to characterize common quails (Coturnix coturnix) in the Azores archipelago and assess the divergence from neighbouring common quail populations. Historical documents suggested that these quails could have a recent origin associated with the arrival of humans in the last centuries. Our results show that Azorean quails constitute a well-differentiated lineage with small size and dark throat pigmentation that has lost the migratory ability and that diverged from mainland quail lineages more than 0.8 mya, contrary to the notion of a recent human-mediated arrival. Even though some Azorean quails carry an inversion that affects 115 Mbp of chromosome 1 and that has been associated with the loss of the migratory behaviour in other common quail populations, half of the analysed individuals do not have that inversion and still do not migrate. The long coexistence and evolution in isolation in the Azores of two chromosomal variants (with and without the inversion) is best explained by balancing selection. Thus, a unique and long evolutionary history led to the island endemic that we know today, C. c. conturbans.
Drawing on the model on financial planning for retirement (FPR), the aim of this work is to explore how parental economic socialization both directly and indirectly affects FPR through the mediation ...of financial literacy, financial planning decisions and financial management. Data from a sample of 280 participants aged between 45 and 63 years were used. The results show that parental economic socialization directly and indirectly influences FPR. Moreover, parental economic behavior acts as a positive model for the development of financial literacy and skills and for decisions about FPR. All the variables increased the explained variance of FPR. Lastly, we discuss the process by which parental economic socialization is positively related to financial literacy and skills that impact on FPR, indicating some implications and future lines of research.
This article tests an integrated model of financial planning for retirement (FPR), with 948 Spanish workers aged between 30 and 63. Overall, the three model dimensions—capacity, willingness, and ...opportunities to plan and save—show a significant association with financial planning for retirement. The moderator role of age in the relationships between antecedents and financial planning was tested. Consistent with our hypothesis, younger participants showed a greater level of FPR if they were characterized by a high level of education. The interaction between both age and psychological preparation for retirement and retirement goals clarity failed to reach statistical significance. We discuss how financial planning effectiveness could be increased based on the results of importance-performance map analyses.
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