'Candidatus Liberibacter europaeus' sp. nov. that is associated with and transmitted by the psyllid Cacopsylla pyri apparently behaves as an endophyte rather than a pathogen

'Candidatus Liberibacter spp.' cause serious plant diseases. 'Candidatus Liberibacter asiaticus', 'Ca. L. americanus' and 'Ca. L. africanus' are the aetiological agents of citrus greening (Huanglongbing) in Asia, America and Africa. 'Candidatus Liberibacter solanacearum' causes diseases in Solanaceae in America and New Zealand. All four species are vectored by psyllid insects of different genera. Here, we show that the pear psyllid pest Cacopsylla pyri (L.) hosts a novel liberibacter species that we named 'Ca. Liberibacter europaeus'. It can bloom to high titres in the psyllid host, with more than 10(9) 16S rRNA gene copies per individual. Fluorescent in situ hybridization experiments showed that 'Ca. L. europaeus' is present in the host midgut lumen, salivary glands and Malpighian tubules. 'Candidatus L. europaeus' has a relatively high prevalence (> 51%) in C. pyri from different areas in the Piedmont and Valle d'Aosta regions in Italy and can be transmitted to pear plants in experimental transmission trials. However, even though high titres of the bacterium (more than 10(8) 16S rRNA gene copies g(-1) of pear plant tissue) could be detected, in the pear tissues no specific disease symptoms could be observed in the infected plants over a 6-month period. Despite liberibacters representing potential quarantine organisms, 'Ca. L. europaeus', first described in Italy and Europe, apparently behaves as an endophyte rather than a pathogen.     

The asthma candidate gene <Emphasis Type="Italic">NPSR1</Emphasis> mediates isoform specific downstream signalling

Background

Neuropeptide S Receptor 1 (NPSR1, GPRA, GPR154) was first identified as an asthma candidate gene through positional cloning and has since been replicated as an asthma and allergy susceptibility gene in several independent association studies. In humans, NPSR1 encodes two G protein-coupled receptor variants, NPSR1-A and NPSR1-B, with unique intracellular C-termini. Both isoforms show distinct expression pattern in asthmatic airways. Although NPSR1-A has been extensively studied, functional differences and properties of NPSR1-B have not yet been clearly examined. Our objective was to investigate downstream signalling properties of NPSR1-B and functional differences between NPSR1-A and NPSR1-B.

Methods

HEK-293 cells transiently overexpressing NPSR1-A or NPSR1-B were stimulated with the ligand neuropeptide S (NPS) and downstream signalling effects were monitored by genome-scale affymetrix expression-arrays. The results were verified by NPS concentration-response and time series analysis using qRT-PCR, cAMP and Ca²⁺ assays, and cAMP/PKA, MAPK/JNK and MAPK/ERK pathway specific reporter assays.

Results

NPSR1-B signalled through the same pathways and regulated the same genes as NPSR1-A, but NPSR1-B yielded lower induction on effector genes than NPSR1-A, with one notable exception, CD69, a marker of regulatory T cells.

Conclusions

We conclude that NPSR1-B is regulating essentially identical set of genes as NPSR1-A, with few, but possibly important exceptions, and that NPSR1-A induces stronger signalling effects than NPSR1-B. Our findings suggest an isoform-specific link to pathogenetic processes in asthma and allergy.

     

Trypanosoma brucei: a model micro-organism to study eukaryotic phospholipid biosynthesis

Although the protozoan parasite, Trypanosoma brucei, can acquire lipids from its environment, recent reports have shown that it is also capable of de novo synthesis of all major phospholipids. Here we provide an overview of the biosynthetic pathways involved in phospholipid formation in T. brucei and highlight differences to corresponding pathways in other eukaryotes, with the aim of promoting trypanosomes as an attractive model organism to study lipid biosynthesis. We show that de novo synthesis of phosphatidylethanolamine involving CDP-activated intermediates is essential in T. brucei and that a reduction in its cellular content affects mitochondrial morphology and ultrastructure. In addition, we highlight that reduced levels of phosphatidylcholine inhibit nuclear division, suggesting a role for phosphatidylcholine formation in the control of cell division. Furthermore, we discuss possible routes leading to phosphatidylserine and cardiolipin formation in T. brucei and review the biosynthesis of phosphatidylinositol, which seems to take place in two separate compartments. Finally, we emphasize that T. brucei represents the only eukaryote so far that synthesizes all three sphingophospholipid classes, sphingomyelin, inositolphosphorylceramide and ethanolaminephosphorylceramide, and that their production is developmentally regulated.     

Response to biotic and oxidative stress in Arabidopsis thaliana: analysis of variably phosphorylated proteins

Protein phosphorylation plays a pivotal role in the regulation of many cellular events; increasing evidences indicate that this post-translational modification is involved in plant response to various abiotic and biotic stresses. Since phosphorylated proteins may be present at low abundance, enrichment methods are generally required for their analysis. We here describe the quantitative changes of phosphoproteins present in Arabidopsis thaliana leaves after challenging with elicitors or treatments mimicking biotic stresses, which stimulate basal resistance responses, or oxidative stress. Phosphoproteins from elicited and control plants were enriched by means of metal oxide affinity chromatography and resolved by 2D electrophoresis. A comparison of the resulting proteomic maps highlighted phosphoproteins showing quantitative variations induced by elicitor treatment; these components were identified by MALDI-TOF peptide mass fingerprinting and/or nanoLC-ESI-LIT-MS/MS experiments. In total, 97 differential spots, representing 75 unique candidate phosphoproteins, were characterized. They are representative of different protein functional groups, such as energy and carbon metabolism, response to oxidative and abiotic stresses, defense, protein synthesis, RNA processing and cell signaling. Ascertained protein phosphorylation found a positive confirmation in available Arabidopsis phosphoproteome database. The role of each identified phosphoprotein is here discussed in relation to plant defense mechanisms. Our results suggest a partial overlapping of the responses to different treatments, as well as a communication with key cellular functions by imposed stresses.     

Leishmania promotes its own virulence by inducing expression of the host immune inhibitory ligand CD200

Leishmania parasites infect macrophages, cells normally involved in innate defense against pathogens. Leishmania amazonensis and Leishmania major cause severe or mild disease, respectively, consistent with each parasite's ability to survive within activated macrophages. The mechanisms underlying increased virulence of L.?amazonensis are mostly unknown. We show that L.?amazonensis promotes its own survival by inducing expression of CD200, an immunoregulatory molecule that inhibits macrophage activation. L.?amazonensis does not form typical nonhealing lesions in CD200(-/-) mice and cannot replicate in CD200(-/-) macrophages, an effect reversed by exogenous administration of soluble CD200-Fc. The less virulent L.?major does not induce CD200 expression and forms small, self-healing lesions in both wild-type and CD200(-/-) mice. Notably, CD200-Fc injection transforms the course of L.?major infection to one resembling L.?amazonensis, with large, nonhealing lesions. CD200-dependent iNOS inhibition allows parasite growth in macrophages, identifying a mechanism for the increased virulence of L.?amazonensis.