Advanced backcross QTL mapping of resistance to Fusarium head blight and plant morphological traits in a <Emphasis Type="Italic">Triticum macha</Emphasis> × <Emphasis Type="Italic">T. aestivum</Emphasis> population

While many reports on genetic analysis of Fusarium head blight (FHB) resistance in bread wheat have been published during the past decade, only limited information is available on FHB resistance derived from wheat relatives. In this contribution, we report on the genetic analysis of FHB resistance derived from Triticum macha (Georgian spelt wheat). As the origin of T. macha is in the Caucasian region, it is supposed that its FHB resistance differs from other well-investigated resistance sources. To introduce valuable alleles from the landrace T. macha into a modern genetic background, we adopted an advanced backcross QTL mapping scheme. A backcross-derived recombinant-inbred line population of 321 BC₂F₃ lines was developed from a cross of T. macha with the Austrian winter wheat cultivar Furore. The population was evaluated for Fusarium resistance in seven field experiments during four seasons using artificial inoculations. A total of 300 lines of the population were genetically fingerprinted using SSR and AFLP markers. The resulting linkage map covered 33 linkage groups with 560 markers. Five novel FHB-resistance QTL, all descending from T. macha, were found on four chromosomes (2A, 2B, 5A, 5B). Several QTL for morphological and developmental traits were mapped in the same population, which partly overlapped with FHB-resistance QTL. Only the 2BL FHB-resistance QTL co-located with a plant height QTL. The largest-effect FHB-resistance QTL in this population mapped at the spelt-type locus on chromosome 5A and was associated with the wild-type allele q, but it is unclear whether q has a pleiotropic effect on FHB resistance or is closely linked to a nearby resistance QTL.     

Pharmacophore-based discovery of FXR agonists. Part I: Model development and experimental validation

The farnesoid X receptor (FXR) is involved in glucose and lipid metabolism regulation, which makes it an attractive target for the metabolic syndrome, dyslipidemia, atherosclerosis, and type 2 diabetes. In order to find novel FXR agonists, a structure-based pharmacophore model collection was developed and theoretically evaluated against virtual databases including the ChEMBL database. The most suitable models were used to screen the National Cancer Institute (NCI) database. Biological evaluation of virtual hits led to the discovery of a novel FXR agonist with a piperazine scaffold (compound 19) that shows comparable activity as the endogenous FXR agonist chenodeoxycholic acid (CDCA, compound 2).     

Mitochondrial protein lipoylation does not exclusively depend on the mtKAS pathway of de novo fatty acid synthesis in Arabidopsis

The photorespiratory Arabidopsis (Arabidopsis thaliana) mutant gld1 (now designated mtkas-1) is deficient in glycine decarboxylase (GDC) activity, but the exact nature of the genetic defect was not known. We have identified the mtkas-1 locus as gene At2g04540, which encodes beta-ketoacyl-[acyl carrier protein (ACP)] synthase (mtKAS), a key enzyme of the mitochondrial fatty acid synthetic system. One of its major products, octanoyl-ACP, is regarded as essential for the intramitochondrial lipoylation of several proteins including the H-protein subunit of GDC and the dihydrolipoamide acyltransferase (E2) subunits of two other essential multienzyme complexes, pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase. This view is in conflict with the fact that the mtkas-1 mutant and two allelic T-DNA knockout mutants grow well under nonphotorespiratory conditions. Although on a very low level, the mutants show residual lipoylation of H protein, indicating that the mutation does not lead to a full functional knockout of GDC. Lipoylation of the pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase E2 subunits is distinctly less reduced than that of H protein in leaves and remains unaffected from the mtKAS knockout in roots. These data suggest that mitochondrial protein lipoylation does not exclusively depend on the mtKAS pathway of lipoate biosynthesis in leaves and may occur independently of this pathway in roots.     

Properties of recombinant glycine decarboxylase P- and H-protein subunits from the cyanobacterium Synechocystis sp. strain PCC 6803

The multi-enzyme complex glycine decarboxylase is important for one-carbon metabolism, essential for the photorespiratory glycolate cycle of plants, and comprises four different polypeptides, P-, H-, T-, and L-protein. We report on the production and properties of recombinant P-protein from the cyanobacterium Synechocystis and also describe features of recombinant H-protein from the same organism. The P-protein shows enzymatic activity with lipoylated H-protein and very low activity with H-apoprotein or lipoate as artificial cofactors. Its affinity towards glycine is unaffected by the presence and nature of the methyleneamine acceptor molecule. The cyanobacterial H-protein apparently forms stable dimers.     

IRAK-4 kinase activity is required for interleukin-1 (IL-1) receptor- and toll-like receptor 7-mediated signaling and gene expression

IRAK-4 is an essential component of the signal transduction complex downstream of the IL-1- and Toll-like receptors. Although regarded as the first kinase in the signaling cascade, the role of IRAK-4 kinase activity versus its scaffold function is still controversial. To investigate the role of IRAK-4 kinase function in vivo, "knock-in" mice were generated by replacing the wild type IRAK-4 gene with a mutant gene encoding kinase-deficient IRAK-4 protein (IRAK-4 KD). IRAK-4 kinase was rendered inactive by mutating the conserved lysine residues in the ATP pocket essential for coordinating ATP. Analyses of embryonic fibroblasts and macrophages obtained from IRAK-4 KD mice demonstrate lack of cellular responsiveness to stimulation with IL-1beta or a Toll-like receptor 7 (TLR7) agonist. IRAK-4 kinase deficiency prevents the recruitment of IRAK-1 to the IL-1 receptor complex and its subsequent phosphorylation and degradation. IRAK-4 KD cells are severely impaired in NFkappaB, JNK, and p38 activation in response to IL-1beta or TLR7 ligand. As a consequence, IL-1 receptor/TLR7-mediated production of cytokines and chemokines is largely absent in these cells. Additionally, microarray analysis identified IL-1beta response genes and revealed that the induction of IL-1beta-responsive mRNAs is largely ablated in IRAK-4 KD cells. In summary, our results suggest that IRAK-4 kinase activity plays a critical role in IL-1 receptor (IL-1R)/TLR7-mediated induction of inflammatory responses.     

Four new hypocretenolides (guaian-12,5-olides) from Leontodon rosani (Asteraceae,Cichorieae)

Subaerial parts of Leontodon rosani (Ten.) DC. collected in the South Italian Basilicata region yielded four new hypocretenolides, 11β,13-dihydro-15-hydroxyhypocretenolide (2), 15-hydroxyhypocretenolide (3), 11β,13-dihydro-15-hydroxyhypocretenolide-β-glucopyranoside (4), and 15-hydroxyhypocretenolide-β-glucopyranoside (5). Structure elucidations were based on MS experiments and extensive one- and two-dimensional NMR experiments. None of the isolated compounds showed any activity in an in vitro acetylcholinesterase inhibition assay. The chemosystematic impact of the occurrence of hypocretenolides in L. rosani is discussed with regards to the supposed allotetraploid origin of the title species. Moreover, HPLC retention times and online mass signals for all currently known hypocretenolide derivatives are described to ease future studies screening for this rare group of natural products.     

Adaptation of the psychrotroph Arthrobacter chlorophenolicus A6 to growth temperature and the presence of phenols by changes in the anteiso/iso ratio of branched fatty acids

Arthrobacter chlorophenolicus is a previously described Gram-positive bacterium capable of degrading high concentrations of several phenolic compounds under optimal mesophilic (28 degrees C) as well as psychrophilic (5 degrees C) conditions. However, the exact mechanisms by which this organism is able to tolerate such extremes in temperature and high levels of toxic compounds are currently not known. In this study, we monitored changes in the fatty acid composition of the cell membrane under different extreme growth conditions. Arthrobacter chlorophenolicus adapts to differences in temperature and phenol concentrations by altering the anteiso/iso ratio of fatty acids in the cell membrane to different extents. According to the different physico-chemical properties of those two species of branched fatty acids, the bacteria showed an increased amount of anteiso fatty acids when grown under psychrophilic conditions to decrease the viscosity of their membranes. On the other hand, at higher growth temperatures as well as in the presence of toxic concentrations of phenol, 4-chlorophenol and 4-nitrophenol, the cells adapted their membrane by a dose-dependent decrease in the anteiso/iso ratio, leading to a more rigid membrane and counteracting the fluidity increase caused by the higher temperature and the organic solvents.