Glycogen metabolic genes are involved in trehalose-6-phosphate synthase-mediated regulation of pathogenicity by the rice blast fungus Magnaporthe oryzae.

© 2013 Badaruddin et al.Editor - Peter N. Dodds, Commonwealth Scientific and Industrial Research Organisation (CSIRO), AustraliaThis work was funded by the Biotechnology and Biological Sciences Research Council and a European Research Council Advanced Investigator Award to NJT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.The filamentous fungus Magnaporthe oryzae is the causal agent of rice blast disease. Here we show that glycogen metabolic genes play an important role in plant infection by M. oryzae. Targeted deletion of AGL1 and GPH1, which encode amyloglucosidase and glycogen phosphorylase, respectively, prevented mobilisation of glycogen stores during appressorium development and caused a significant reduction in the ability of M. oryzae to cause rice blast disease. By contrast, targeted mutation of GSN1, which encodes glycogen synthase, significantly reduced the synthesis of intracellular glycogen, but had no effect on fungal pathogenicity. We found that loss of AGL1 and GPH1 led to a reduction in expression of TPS1 and TPS3, which encode components of the trehalose-6-phosphate synthase complex, that acts as a genetic switch in M. oryzae. Tps1 responds to glucose-6-phosphate levels and the balance of NADP/NADPH to regulate virulence-associated gene expression, in association with Nmr transcriptional inhibitors. We show that deletion of the NMR3 transcriptional inhibitor gene partially restores virulence to a Δagl1Δgph1 mutant, suggesting that glycogen metabolic genes are necessary for operation of the NADPH-dependent genetic switch in M. oryzae.Biotechnology and Biological Sciences Research Council (BBSRC)European Research Council (ERC

Evidence From the Use of Monoclonal-Antibody Probes for Structural Heterogeneity of the Growth-Hormone Receptor

1. We describe the use of four monoclonal antibodies (MAbs) to the rabbit liver growth hormone (GH) receptor and one raised against purified rat liver GH receptor to characterize liver receptor subtypes which differ in their hormone-binding regions. 2. The anti-(rat liver GH receptor) MAb both inhibited and precipitated rat and rabbit GH receptors, but only one-half of I-oGH (ovine GH) binding to liver microsomes could be inhibited by excess antibody. Conversely, only one-half of I-anti-(rat GH receptor) MAb binding was inhibited by excess oGH and Scatchard plots for this MAb exhibited two components. Although only 50% of I-oGH binding to membranes was inhibited by this MAb, all solubilized receptor could be immunoprecipitated. 3. We postulate two epitopes for the anti-(rat GH receptor) MAb, one located at the hormone-binding site (inhibitory site) and one elsewhere (immunoprecipitating site). 4. A second, rabbit-specific antibody (MAb 7) inhibited 85% of hormone binding but only 30% of I-anti-(rat GH receptor) MAb binding to rabbit liver microsomes. A combination of this MAb with the anti-(rat GH receptor) MAb totally inhibited I-oGH binding. MAb 7 alone totally inhibited I-rat GH binding to rabbit liver microsomes, as it did with I-oGH binding to purified receptor. 5. On the basis of these results and others we postulate three types of GH receptor in rabbit liver membranes and ascribe approximate extents of I-oGH binding to each. 6. A cytosolic 'GH receptor' which is not poly(ethylene glycol)-precipitable is shown to share five epitopes with 'type 2' microsomal receptors. 7. Purified plasma membrane and endoplasmic reticulum fractions derived from a rabbit liver microsomal preparation have identical antigenic characteristics with respect to the GH-binding region, indicating that the heterogeneity we describe is not related to receptor processing. 8. Of the three types of GH receptor in the plasma membrane of the rabbit (and possibly rat) we postulate that one (type 1) corresponds to the GH receptor involved in stimulating growth and possesses all of the epitopes studied here. A second (type 2) appears to be identical with the cytosolic 'GH receptor' and lacks the epitope for the anti-(rat GH receptor) MAb in the hormone binding site region. A third (type 3) does not possess the epitope for the inhibitory anti-(rabbit GH receptor) MAb, appears not to bind rat GH and is lost during purification. 9. The availability of type-specific MAbs will facilitate assignment of specific functions to liver receptor subtypes which mediate the multiple functions of GH

Immunocytochemical studies on the localization of 5-aminolevulinate synthase in rat liver

The localization of 5-aminolevulinate synthase (ALAS) in hepatocytes of untreated and porphyrinogenic drug-treated animals has been examined by an immunocytochemical approach using a monoclonal antibody and protein A-gold labeling. Gold particles representing antigenic sites for ALAS were observed in the mitochondria and cytoplasm of untreated and drug-treated cells. Quantitative analysis of the labeling density showed that levels of ALAS increased significantly in both of these cellular compartments following drug treatment. Evidence that the detected cytoplasmic form of ALAS represents the precursor of the enzyme was obtained from immunoblotting experiments. The direct detection of cytosolic ALAS in vivo rules out the possibility that enzyme activity previously detected in the cytosol fraction resulted from mitochondrial leakage during cell fractionation. The results indicate that the cytosolic accumulation of ALAS is not a consequence of the inability of mitochondria to accommodate more enzyme. However, the molecular basis for this cytosolic accumulation is not known. The studies also established that the mitochondrial enzyme is predominantly, if not exclusively, associated with the matrix side of the inner mitochondrial membrane.link_to_subscribed_fulltex

Imaging of deep venous thrombosis in patients using a radiolabelled anti-D-dimer Fab′ fragment (99mTc-DI-DD3B6/22-80B3): results of a phase I trial

Purpose 99mTc-DI-DD3B6/22-80B3 (ThromboView®, hereafter abbreviated to 99mTc-DI-80B3 Fab′) is a radiolabelled humanised monoclonal Fab′ fragment with affinity and specificity for D-dimer domains of cross-linked fibrin. Detection of thromboembolic events has been demonstrated in canine models. The study objectives were evaluation of safety and characterisation of biodistribution, immunogenicity and pharmacokinetic profile of increasing doses of 99mTc-DI-80B3 Fab′ in subjects with acute lower-limb DVT. Methods Twenty-six patients with acute lower limb DVT were enrolled. Of these, 21 received a single intravenous dose of 0.5 mg (n = 6), 1.0 mg (n = 9) or 2 mg (n = 6) 99mTc-DI-80B3 Fab′. Blood and urine samples and gamma camera images were collected to 24 h after administration for pharmacokinetic and dosimetry analysis. Vital signs, electrocardiography, hematological and biochemical data and human anti-human antibody (HAHA) levels were monitored for up to 30 days following administration. Patients were assigned to either planar or single photon emission computed tomographic (SPECT) imaging of the thorax at 4 h following injection. Results Thirty-five adverse events were reported in 15 of the 21 subjects. Those deemed possibly related to administration of 99mTc-DI-80B3 Fab′ included mild hypertension, mild elevation of LD (lactate dehydrogenase) and moderate elevation of ALT (alanine transaminase). HAHA assays remained negative. Pharmacokinetics and organ dosimetry were comparable to prior normal volunteer data. Localisation of Thromboview® to sites of known thrombus was evident as early as 30 min post-injection. Conclusions In subjects with acute DVT, 99mTc-DI-80B3 Fab′ was well tolerated with favourable characteristics for the detection of acute venous thrombosis