XopR, a type III effector secreted by Xanthomonas oryzae pv. oryzae, suppresses microbe-associated molecular pattern-triggered immunity in Arabidopsis thaliana

Xanthomonas oryzae pv. oryzae is the causal agent of bacterial blight of rice. The XopR protein, secreted into plant cells through the type III secretion apparatus, is widely conserved in xanthomonads and is predicted to play important roles in bacterial pathogenicity. Here, we examined the function of XopR by constructing transgenic Arabidopsis thaliana plants expressing it under control of the dexamethasone (DEX)-inducible promoter. In the transgenic plants treated with DEX, slightly delayed growth and variegation on leaves were observed. Induction of four microbe-associated molecular pattern (MAMP)-specific early-defense genes by a nonpathogenic X. campestris pv. campestris hrcC deletion mutant were strongly suppressed in the XopR-expressing plants. XopR expression also reduced the deposition of callose, an immune response induced by flg22. When transiently expressed in Nicotiana benthamiana, a XopR::Citrine fusion gene product localized to the plasma membrane. The deletion of XopR in X. oryzae pv. oryzae resulted in reduced pathogenicity on host rice plants. Collectively, these results suggest that XopR inhibits basal defense responses in plants rapidly after MAMP recognition.     

Comparison of methane, nitrous oxide fluxes and CO2 respiration rates from a Mediterranean cork oak ecosystem and improved pasture

Background and aims

During the recent decades, cork oak (Q. suber) mortality has been increasing in Mediterranean oak woodland endangering the economical and environmental sustainability of the “montado” ecosystem. This fact in combination with climate change and conversion of forestland to pasture may significantly affect the soil-atmosphere greenhouse gases (GHGs) exchange. Our study evaluates the impact of oak trees as compared to pasture on net ecosystem GHG (CH_4, N₂O, and CO₂) exchange as well as the main environmental factors influencing this exchange.

Methods

We used field chamber measurements for the collection of GHGs under three different conditions: 1) open area (OA), 2) under tree canopy area (UC) and 3) improved pasture (IP). Experiments were done under typical Mediterranean climate at central Portugal in 2010 and 2011.

Results

The UC had higher nitrification potential, soil C/N ratio, electrical conductivity, litter input and soil organic matter (SOM) than OA and IP. SOM positively correlated with soil CH₄ and N₂O fluxes but not with soil CO₂ respiration rates. Soil water content (SWC) drives both CH₄ and N₂O fluxes. Under certain conditions, when SWC reached a threshold (7 % for CH₄ and 3 % for N₂O) the result was net uptake and that net uptake increased with SWC. This was the case for the UC and OA. Conversely, for the IP soil water content above 4 % promoted net CH₄ release.

Conclusions

Our results show that cork oak influences soil properties and consequently GHGs fluxes. In the UC the input of litter for SOM together with soil moisture, favoured microbiological activity and related GHGs fluxes. Soil temperature is a secondary factor in the studied conditions. Our results also emphasized the potential impact posed by decreased cork oak tree density in the functioning of the “montado” ecosystem.     

Endogenous macrophage migration inhibitory factor modulates glucocorticoid sensitivity in macrophages via effects on MAP kinase phosphatase-1 and p38 MAP kinase

The pro-inflammatory cytokine macrophage migration inhibitory factor (MIF) is induced by glucocorticoids (GCs), but it was not previously known if MIF regulates cellular sensitivity to GC. Here we show in GC and LPS-treated peritoneal macrophages derived from MIF-/- and wt mice that the absence of endogenous MIF is associated with increased sensitivity to GC of TNF release. This is associated with increased expression of mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1), concomitant decreased phosphorylation of p38 MAPK, but no effect of MIF on nuclear factor kappaB (NF-kappaB). These results demonstrate that MIF regulates GC sensitivity by phosphorylation of p38, and provides a cellular mechanism for this observation, indicating that MKP-1 is a central target of this regulation.     

Synthesis and antidepressant-like action of stereoisomers of imidobenzenesulfonylaziridines in mice evaluated in the forced swimming test

The present study describes the chemical synthesis and pharmacological evaluation of a new series of eleven compounds stereoisomers of imidobenzenesulfonylaziridines in the forced-swimming test (FST) in mice. The pharmacological results of these compounds show that six of them, given intraperitoneally, reduced the immobility time of mice evaluated in the FST, an antidepressant-like profile of action similar to imipramine, a well-known standard antidepressant drug used for comparison, without compromising the animals' motor performance. The putative antidepressant-like action demonstrated here indicates their viability for the development of new therapeutic options for the treatment of depression.     

MITOCHONDRIAL DNA PHYLOGENY OF THE SYMBIOTIC DINOFLAGELLATES (SYMBIODINIUM,DINOPHYTA)1

Symbiotic dinoflagellates belonging to the genus Symbiodinium (Freudenthal) are found worldwide in association with shallow‐water tropical and subtropical marine invertebrates. Most phylogenetic studies of Symbiodinium have used nuclear rRNA (nrDNA) genes to infer relationships among members of the genus. In this report, we present the first phylogeny of Symbiodinium based on DNA sequences from a mitochondrial protein‐coding gene (cytochrome oxidase subunit I [cox1]). Two principal groups, one comprised of Symbiodinium clade A and the second encompassing Symbiodinium clades B/C/D/E/F, are strongly supported in the cox1 phylogeny. Relationships within Symbiodinium clades B/C/D/E/F, however, are less well resolved compared with phylogenies inferred from nrDNA and chloroplast large subunit (cp23S)‐rDNA genes. Statistical tests between alternative tree topologies verified, with an exception being the position of one controversial member of Symbiodinium clade D, that relationships inferred from cox1 are congruent with those inferred from nrDNA and cp23S‐rDNA. Taken together, the relationships between the major Symbiodinium clades are robust, and there appears to be no evidence of hybridization or differential introgression of nuclear and plastid genomes between clades.     

Vitamin E or coenzyme Q10 administration is not fully advantageous for heart mitochondrial function in diabetic goto kakizaki rats

The heart is one of the organs affected during the later stages of diabetes. Mitochondrial function has already been proposed to be affected during the course of diabetes. Nevertheless, little information is known concerning the impact of antioxidants in heart mitochondria of a milder model for diabetes, such as the Goto-Kakizaki (GK) rat, where mitochondrial function appears ameliorated. The objective of this work was to test if injections of Vitamin E and Coenzyme Q10, alone and in combination, were able to modify mitochondrial performance in the hearts of GK rats. Several aspects of mitochondrial function were measured, such as the respiratory control ratio and the electric potential, as well as the mitochondrial accumulation of Vitamin E and Coenzymes Q9 and Q10. We observed that only Vitamin E appeared to have a positive impact on the mitochondrial phosphorylation efficiency and on mitochondrial performance, namely on the ability to generate the electric transmembrane potential in the presence of supra-physiological calcium concentrations. Vitamin E administration also increased the mitochondrial concentration of Coenzyme Q10. None of the treatments was able to reverse the diabetic phenotype in GK rats. We conclude that in this model of mild hyperglycemia, administration of antioxidants may have a marginal positive impact on mitochondrial function.     

Dammarane triterpenes from Cabralea canjerana (Vell.) Mart. (Meliaceae): Their chemosystematic significance

The stem of Cabralea canjerana (Vell.) Mart. yielded three new dammarane triterpenes 20S,24S-epoxy-7β,25-dihydroxy-3,4-secodammar-4(28)-en-3-oic acid, 20S,24S-epoxy-7β,15α,25-trihydroxy-3,4-secodammar-4(28)-en-3-oic acid and 20S,24R-epoxy-7β,22ξ,25-trihydroxy-3,4-secodammar-4(28)-en-3-oic acid, which were identified on the basis of spectroscopic methods. The known dammarane triterpenes ocotillone, eichlerianic acid, shoreic acid and the sterols sitosterol, campesterol, stigmasterol, sitostenone and stigmast-5-en-3-one were also isolated and identified. The branches yielded the above three known dammaranes and eichlerialactone. The dammaranes in C. canjerana display strong similarities with Trichilieae tribe, which contains several dammaranes. The data reported herein thus provide firm support for placing Cabralea within the subfamily Melioideae, Trichilieae tribe.     

Cutaneous alternariosis in a liver transplant recipient

We describe the case of a liver transplant patient with a cutaneous alternariosis due to Alternaria infectoria. Cutaneous lesions regressed with the decrease in daily doses of immunosuppressors. The skin lesion remains cicatricial after one year of follow-up.     

Role of SERK genes in plant environmental response

In plants, cell signaling connects the environmental input to the intracellular responses in plants. Exogenous signals play an important role in cell metabolism leading to growth and defense responses. Some of these stimuli induce anatomical and physiological modifications that are generally modulated by gene expression. SERK belongs to a small family of genes that code for a transmembrane protein involved in signal transduction and that have been strongly associated with somatic embryogenesis and apomixis in a number of plant species. Recent studies corroborate its role in somatic embryogenesis and suggest a broader range of functions in plant response to biotic and abiotic stimuli. This mini-review aims to present new data on SERK and discuss its involvement in plant development as well as in response to environmental stress.Key words: SERK, fungus tolerance, environmental stress, brassinosteroids, SAR