Parasitic modulation of host development by ubiquitin-independent protein degradation

Certain obligate parasites induce complex and substantial phenotypic changes in their hosts in ways that favor their transmission to other trophic levels. However, the mechanisms underlying these changes remain largely unknown. Here we demonstrate how SAP05 protein effectors from insect-vectored plant pathogenic phytoplasmas take control of several plant developmental processes. These effectors simultaneously prolong the host lifespan and induce witches’ broom-like proliferations of leaf and sterile shoots, organs colonized by phytoplasmas and vectors. SAP05 acts by mediating the concurrent degradation of SPL and GATA developmental regulators via a process that relies on hijacking the plant ubiquitin receptor RPN10 independent of substrate ubiquitination. RPN10 is highly conserved among eukaryotes, but SAP05 does not bind insect vector RPN10. A two-amino-acid substitution within plant RPN10 generates a functional variant that is resistant to SAP05 activities. Therefore, one effector protein enables obligate parasitic phytoplasmas to induce a plethora of developmental phenotypes in their hosts

Prospects for the development of probiotics and prebiotics for oral applications

There has been a paradigm shift towards an ecological and microbial community-based approach to understanding oral diseases. This has significant implications for approaches to therapy and has raised the possibility of developing novel strategies through manipulation of the resident oral microbiota and modulation of host immune responses. The increased popularity of using probiotic bacteria and/or prebiotic supplements to improve gastrointestinal health has prompted interest in the utility of this approach for oral applications. Evidence now suggests that probiotics may function not only by direct inhibition of, or enhanced competition with, pathogenic micro-organisms, but also by more subtle mechanisms including modulation of the mucosal immune system. Similarly, prebiotics could promote the growth of beneficial micro-organisms that comprise part of the resident microbiota. The evidence for the use of pro or prebiotics for the prevention of caries or periodontal diseases is reviewed, and issues that could arise from their use, as well as questions that still need to be answered, are raised. A complete understanding of the broad ecological changes induced in the mouth by probiotics or prebiotics will be essential to assess their long-term consequences for oral health and disease

Voorlopige en definitieve oplevering, inontvangstneming en aanvaarding: what’s in a name?

status: publishe

Polyspecies biofilm formation on implant surfaces with different surface characteristics

OBJECTIVE: To investigate the microbial adherence and colonization of a polyspecies biofilm on 7 differently processed titanium surfaces. MATERIAL AND METHODS: Six-species biofilms were formed anaerobically on 5-mm-diameter sterilized, saliva-preconditioned titanium discs. Material surfaces used were either machined, stained, acid-etched or sandblasted/acid-etched (SLA). Samples of the latter two materials were also provided in a chemically modified form, with increased wettability characteristics. Surface roughness and contact angles of all materials were determined. The discs were then incubated anaerobically for up to 16.5 h. Initial microbial adherence was evaluated after 20 min incubation and further colonization after 2, 4, 8, and 16.5 h using non-selective and selective culture techniques. Results at different time points were compared using ANOVA and Scheffé post hoc analysis. RESULTS: The mean differences in microorganisms colonizing after the first 20 min were in a very narrow range (4.5 to 4.8 log CFU). At up to 16.5 h, the modified SLA surface exhibited the highest values for colonization (6.9±0.2 log CFU, p<0.05) but increasing growth was observed on all test surfaces over time. Discrepancies among bacterial strains on the differently crafted titanium surfaces were very similar to those described for total log CFU. F. nucleatum was below the detection limit on all surfaces after 4 h. CONCLUSION: Within the limitations of this in vitro study, surface roughness had a moderate influence on biofilm formation, while wettability did not seem to influence biofilm formation under the experimental conditions described. The modified SLA surface showed the highest trend for bacterial colonization

Organic wheat quality from a defined Italian field-trial

Organic and conventional wheat grain (Triticum aestivum and Triticum durum) samples coming from a defined field trial in Italy were measured in 2005 and 2006 for their total protein content and the contents of lutein and zeaxanthin. Additionally the samples were analyzed by means of the biocrystallization method. The grain samples could be differentiated by the total protein content, which was higher in the conventional samples. The organic samples contained a higher lutein content in Triticum aestivum but lower in Triticum durum. Biocrystallization differentiated Triticum durum from Triticum aestivum and organic from conventional grown samples when visual evaluation was applied. Differentiation of farming systems was possible for biocrystallization evaluated with computerized texture analysis but not significant for all samples and years

Widespread targeting of development-related host transcription factors by phytoplasma effectors

1AbstractPhytoplasmas are pathogenic bacteria that reprogram plant host development in order to attract their insect vectors to disseminate. Previous studies have characterized a few different phytoplasma effector proteins that supress specific transcription factors. However, these are only a small fraction of the potential effectors used by phytoplasmas, meaning that the molecular mechanisms through which phytoplasmas manipulate their hosts are largely uncharacterized. To obtain further insights into the phytoplasma infection mechanisms, we generated a protein-protein interaction network between a broad set of phytoplasma effectors and a large collection ofArabidopsis thalianatranscription factors and transcriptional regulators. We found widespread, but unique, interactions with host transcription factors by phytoplasma effectors, especially those related to developmental processes. In particular, many unrelated effectors target TCP transcription factors, which play roles in plant development and immunity. Comparison with other host-pathogen protein interaction networks shows that phytoplasma effectors have unusual targets, and indicates that phytoplasmas have evolved a unique and unusual infection strategy. This study provides a rich and solid data source that can be used to predict functional effects of individual effectors and as a guide for detailed studies of individual effectors in the future, as well as insights into the underlying molecular mechanisms of phytoplasma infection.2Significance statementThis work shows that the effectors of phytoplasma, a bacterial plant pathogen, show pervasive interactions with development-related host transcription factors, providing a way to take over plant growth and development in favor of the pathogen and its insect vector. The obtained comprehensive protein interaction network and showcase of the potential biological consequences of a selected effector advance our understanding of phytoplasma-host interactions and provide guidance for further study.</jats:sec

Arabidopsis thaliana ambient temperature responsive lncRNAs

Background: Long non-coding RNAs (lncRNAs) have emerged as new class of regulatory molecules in animals where they regulate gene expression at transcriptional and post-transcriptional level. Recent studies also identified lncRNAs in plant genomes, revealing a new level of transcriptional complexity in plants. Thousands of lncRNAs have been predicted in the Arabidopsis thaliana genome, but only a few have been studied in depth. Results: Here we report the identification of Arabidopsis lncRNAs that are expressed during the vegetative stage of development in either the shoot apical meristem or in leaves. We found that hundreds of lncRNAs are expressed in these tissues, of which 50 show differential expression upon an increase in ambient temperature. One of these lncRNAs, FLINC, is down-regulated at higher ambient temperature and affects ambient temperature-mediated flowering in Arabidopsis. Conclusion: A number of ambient temperature responsive lncRNAs were identified with potential roles in the regulation of temperature-dependent developmental changes, such as the transition from the vegetative to the reproductive (flowering) phase. The challenge for the future is to characterize the biological function and molecular mode of action of the large number of ambient temperature-regulated lncRNAs that have been identified in this study.</p