Subcellular localization requirements and specificities for plant immune receptor Toll-interleukin-1 receptor signaling.

Recent work shed light on how plant intracellular immune receptors of the nucleotide-binding leucine-rich repeat (NLR) family are activated upon pathogen effector recognition to trigger immune responses. Activation of Toll-interleukin-1 receptor (TIR) domain-containing NLRs (TNLs) induces receptor oligomerization and close proximity of the TIR domain, which is required for TIR enzymatic activity. TIR-catalyzed small signaling molecules bind to EDS1 family heterodimers and subsequently activate downstream helper NLRs, which function as Ca2+ permeable channel to activate immune responses eventually leading to cell death. Subcellular localization requirements of TNLs and signaling partners are not well understood, although they are required to understand fully the mechanisms underlying NLR early signaling. TNLs show diverse subcellular localization while EDS1 shows nucleocytosolic localization. Here, we studied the impact of TIR and EDS1 mislocalization on the signaling activation of different TNLs. In Nicotiana benthamiana, our results suggest that close proximity of TIR domains isolated from flax L6 and Arabidopsis RPS4 and SNC1 TNLs drives signaling activation from different cell compartments. Nevertheless, both Golgi-membrane anchored L6 and nucleocytosolic RPS4 have the same requirements for EDS1 subcellular localization in Arabidopsis thaliana. By using mislocalized variants of EDS1, we found that autoimmune L6 and RPS4 TIR domain can induce seedling cell death when EDS1 is present in the cytosol. However, when EDS1 is restricted to the nucleus, both induce a stunting phenotype but no cell death. Our data point out the importance of thoroughly investigating the dynamics of TNLs and signaling partners subcellular localization to understand TNL signaling fully.

Evaluation of a Non-Parenteral Opioid Analgesia Protocol for Acute Sickle Cell Pain Episodes in Children.

We evaluated a protocol comprising intranasal diamorphine (IND) combined with oral short and modified-release morphine for children at the emergency department (ED) with acute painful episodes of sickle cell disease (SCD). In a retrospective audit of 83 episodes in 38 children, the mean time between arrival in the treatment area and the administration of IND was 10 min (range <5 min to 1.39 h). IND was administered in <5 min in 43 (51.6%), and in <20 min in 75 (90.4%) episodes. Persisting pain, requiring background analgesia with modified-release oral morphine, was required in 25 (30.1%) episodes. Inadequate control of pain requiring a switch to intravenous morphine PCA was required in eight episodes in four patients. Acute chest syndrome (ACS) developed in four of 83 episodes (4.8%, 95% CI 0.2-9.4%) and in four of 38 children (10.5%, 95% CI 0.7-20.5%). In conclusion, this protocol enabled the rapid administration of strong opioid analgesia in an ED setting, and may reduce the short and long-term adverse effects associated with parenteral opioids in children. There was no evidence of an increased incidence of ACS associated with use of oral morphine.

Loss of AvrSr50 by somatic exchange in stem rust leads to virulence for Sr50 resistance in wheat.

Race-specific resistance genes protect the global wheat crop from stem rust disease caused by Puccinia graminis f. sp. tritici (Pgt) but are often overcome owing to evolution of new virulent races of the pathogen. To understand virulence evolution in Pgt, we identified the protein ligand (AvrSr50) recognized by the Sr50 resistance protein. A spontaneous mutant of Pgt virulent to Sr50 contained a 2.5 mega-base pair loss-of-heterozygosity event. A haustorial secreted protein from this region triggers Sr50-dependent defense responses in planta and interacts directly with the Sr50 protein. Virulence alleles of AvrSr50 have arisen through DNA insertion and sequence divergence, and our data provide molecular evidence that in addition to sexual recombination, somatic exchange can play a role in the emergence of new virulence traits in Pgt.

Transcranial Doppler Screening in a Regional Care Network for Sickle Cell Disease in the United Kingdom.

The risk of stroke in children screened with transcranial Doppler ultrasound in the United Kingdom is not known. We evaluated a clinician-led program using a risk assessment modified from the STOP protocol. High-risk classification included abnormal velocities in the anterior cerebral artery, and single abnormal scan if initial velocity >220 cm/s (high abnormal) or if preceded by at least 2 conditional scans. In total, 1653 scans were performed in 542 children, followed for 2235 patient-years. Fifty-eight (10.7%) high-risk subjects were identified, including 18 (31%) with high abnormal, and 15 (26%) with previous conditional scans. In 2 (3%), abnormal velocity was restricted to the anterior cerebral artery. The estimated proportion of children at high risk, scanned before 6 years of age was >20%. There were 4 cases of acute ischemic stroke (AIS) and 2 of acute hemorrhagic stroke. The incidence of all stroke, AIS, and acute hemorrhagic stroke were 0.27, 0.18, and 0.09 per 100 patient-years, respectively. The proportion of children at high risk is higher than most previous estimates, partly as a result of our modified risk assessment. About 2 children per 1000 screened with transcranial Doppler ultrasound progress to AIS.

Comparative Analysis of the Flax Immune Receptors L6 and L7 Suggests an Equilibrium-Based Switch Activation Model.

NOD-like receptors (NLRs) are central components of the plant immune system. L6 is a Toll/interleukin-1 receptor (TIR) domain-containing NLR from flax (Linum usitatissimum) conferring immunity to the flax rust fungus. Comparison of L6 to the weaker allele L7 identified two polymorphic regions in the TIR and the nucleotide binding (NB) domains that regulate both effector ligand-dependent and -independent cell death signaling as well as nucleotide binding to the receptor. This suggests that a negative functional interaction between the TIR and NB domains holds L7 in an inactive/ADP-bound state more tightly than L6, hence decreasing its capacity to adopt the active/ATP-bound state and explaining its weaker activity in planta. L6 and L7 variants with a more stable ADP-bound state failed to bind to AvrL567 in yeast two-hybrid assays, while binding was detected to the signaling active variants. This contrasts with current models predicting that effectors bind to inactive receptors to trigger activation. Based on the correlation between nucleotide binding, effector interaction, and immune signaling properties of L6/L7 variants, we propose that NLRs exist in an equilibrium between ON and OFF states and that effector binding to the ON state stabilizes this conformation, thereby shifting the equilibrium toward the active form of the receptor to trigger defense signaling.

Three sucrose transporter genes are expressed in the developing grain of hexaploid wheat.

A family of three cDNAs, designated TaSUT1A, 1B and 1D, encoding sucrose transporter (SUT) proteins was isolated from a hexaploid wheat (Triticum aestivum) endosperm library. The cDNA sequences are 96% identical but are distinguishable from one another by virtue of a size polymorphism in the 3'-untranslated region (UTR). The predicted amino acid sequences are 98% identical and are highly similar to the sucrose transporters from rice, maize and barley. A gene for TaSUT1 was isolated from genomic libraries of Aegilops tauschii (the donor of the D genome of wheat) and the coding sequence found to be identical to that of TaSUT1D cDNA. There is only one copy of each TaSUT1 gene in hexaploid wheat and it is located on chromosome 4. Genomic Southern analysis and PCR analysis across the 3' polymorphic region of hexaploid, tetraploid and progenitor diploid wheat DNAs established that the TaSUT1A gene was present in the putative A-genome progenitor, T. monococcum, and that the TaSUT1B gene was present in the putative B-genome progenitor, T. searsii. All three TaSUT1 genes are expressed at high levels in filling grain, showing a good correlation with the developmental time course of growth. This reinforces the view that in cereals a major role of SUT1 is in the post-phloem sugar transport pathway associated with seed filling.