Identification of a UDP-glucosyltransferase conferring deoxynivalenol resistance in Aegilops tauschii and wheat

Aegilops tauschii is the diploid progenitor of the wheat D subgenome and a valuable resource for wheat breeding, yet, genetic analysis of resistance against Fusarium head blight (FHB) and the major Fusarium mycotoxin deoxynivalenol (DON) is lacking. We treated a panel of 147 Ae. tauschii accessions with either Fusarium graminearum spores or DON solution and recorded the associated disease spread or toxin-induced bleaching. A k-mer-based association mapping pipeline dissected the genetic basis of resistance and identified candidate genes. After DON infiltration nine accessions revealed severe bleaching symptoms concomitant with lower conversion rates of DON into the non-toxic DON-3-O-glucoside. We identified the gene AET5Gv20385300 on chromosome 5D encoding a uridine diphosphate (UDP)-glucosyltransferase (UGT) as the causal variant and the mutant allele resulting in a truncated protein was only found in the nine susceptible accessions. This UGT is also polymorphic in hexaploid wheat and when expressed in Saccharomyces cerevisiae only the full-length gene conferred resistance against DON. Analysing the D subgenome helped to elucidate the genetic control of FHB resistance and identified a UGT involved in DON detoxification in Ae. tauschii and hexaploid wheat. This resistance mechanism is highly conserved since the UGT is orthologous to the barley UGT HvUGT13248 indicating descent from a common ancestor of wheat and barley.     

The int genes of bacteriophages P22 and λ are regulated by different mechanisms

Bacteriophage P22 and λ are related bacteriophages with similar gene organizations. In λ the cII-dependent P_I promoter is responsible for λint gene expression. The only apparent counterpart to P_I in P22 is oriented in the opposite direction, and cannot transcribe the P22 int gene. We show that this promoter, called P_al, is active both in vivo and in vitro, and is dependent upon the P22 cII-like gene, called c1. We have also determined the DNA sequence of a 3.3 kb segment that closes the gap between previously reported sequences to give a continuous sequence between the P22 p_L promoter and the int gene. The newly determined sequence is densely packed with genes from the p_L direction, and the proteins predicted by the sequence show excellent correlation with the proteins mapped by Youderian and Susskind in 1980. However, the sequence contains no apparent genes in the opposite (p_al) direction, and no additional binding motifs for the P22 c1 protein. We conclude that int gene expression in P22 is regulated by a different mechanism than in λ.     

A new species of Inonotus (Hymenochaetaceae) from Scandinavia

The new species Inonotus ulmicola belongs to the Inonotus obliquus complex. It is separated by the presence of solitary tramal setae, and by growing on Ulmus , and is reported from Denmark and Sweden. A survey is presented of the species of Inonotus growing in trunk cavities and beneath the bark, and a classification of the setae is proposed.     

The cytidylyltransferase superfamily: Identification of the nucleotide-binding site and fold prediction

The crystal structure of glycerol-3-phosphate cytidylyltransferase from B. subtilis (TagD) is about to be solved. Here, we report a testable structure prediction based on the identification by sequence analysis of a superfamily of functionally diverse but structurally similar nucleotide-binding enzymes. We predict that TagD is a member of this family. The most conserved region in this superfamily resembles the ATP-binding HiGH motif of class I aminoacyI-tRNA synthetases. The predicted secondary structure of cytidylyltransferase and its homologues is compatible with the α/β topography of the class I aminoacyl-tRNA synthetases. The hypothesis of similarity of fold is strengthened by sequence-structure alignment and 3D model building using the known structure of tyrosyl tRNA synthetase as template. The proposed 3D model of TagD is plausible both structurally, with a well packed hydrophobic core, and functionally, as the most conserved residues cluster around the putative nucleotide binding site. If correct, the model would imply a very ancient evolutionary link between class I tRNA synthetases and the novel cytidylyltransferase superfamily. © 1995 Wiley-Liss, Inc.     

Occurrence of α-acetolactate decarboxylases among lactic acid bacteria and their utilization for maturation of beer

Summary Acetolactate decarboxylase activity has been detected among three genera, nine species and 263 strains of lactic acid bacteria tested in the course of a screening for acetolactate decarboxylases amenable for use in brewing as maturation aid. Streptococcus diacetylactis strain FD-64-D was found to generate a decarboxylase exhibiting a satisfactory activity and an excellent stability at the pH prevailing in beer and wort. This decarboxylase could not be solubilized but enzymatically active, freeze-dried cells were effective for satisfactory flavour maturation of beer although difficulties were encountered during attempts to remove the applied cell material by filtration of the beer. Lactobacillus casei DSM 2547 was likewise found to produce a decarboxylase exhibiting a satisfactory activity and stability at the low pH of beer and which, in addition, was readily solubilized. A method has been developed for pilot scale production of preparations of this decarboxylase suitable for use in brewing.Abbreviations DSM Deutsche Sammlung von Microorganismen - EDTA Ethylene diaminetetra-acetic acid     

Methane oxidation by methanotrophs and its effects on the phosphate flux over the sediment-water interface in a eutrophic lake

The effect of methane oxidation in aerobic sediment on oxygen consumption and phosphate flux was investigated in diffusion chambers. The diffusion chambers consisted of two compartments separated by a Teflon membrane. In the upper chamber a thin sediment layer was present and the lower chamber was continuously flushed with gas. The hydrophobic membrane allowed for diffusion of gases from the lower chamber through the sediment layer toward the headspace of the upper chamber. In experiments with a methane oxidation rate of 9.8 mmol m^–2 day^–1, the oxygen consumption rate increased by a factor of two compared with controls without methane oxidation (8.6 vs 17.7 mmol m^–2 day^–1). Methane oxidation significantly decreased oxygen penetration depth (2.5–4.0 vs 1.0–2.0 mm). However, despite the shrinkage of the oxidized microlayer, no differences were found in phosphate flux across the sediment water interface. Batch experiments with standard additions of methane revealed that the growth of methanotrophic bacteria contributes to the phosphate uptake of aerobic sediment. From the batch experiments a molar ratio of carbon to phosphate of 45 mol:mol was calculated for the growth of methanotrophs. Results suggest that a decrease in chemical phosphate adsorption caused by a decrease in the oxygen penetration depth could be compensated for entirely by the growth of methanotrophic bacteria. Send offprint requests to: A.J.C. Sinke     

Quantitative structure-activity relationships (QSAR) in sweet aspartyl dipeptide methyl esters

In drug design the pharmacochemists frequently use physicochemicalconstants to correlate the structure with the observed potency.Curiously this approach has hardly been followed by psychophysiciststo indicate the increase of taste potency in a series of structurallyrelated compounds of the same stimulus. In the present experiments we correlated the relative sweetness(S) of 40 aspartyl dipeptide methyl esters [general formulaCH₂(COO^–). CH(NH₃⁺ ).CO.NH.CH(R).COOCH₃] with 8 physicochemicalparameters. Among the compounds we had 7 non-sweet stimuli whilethe potency of the remaining 33 peptide esters varied from 1to 27,000 (1 = sucrose). We calculated for the side chain Rthe values of the parachor parameter P, the hydrophobic fragmentalconstant f and 5 STERIMOL parameters (L, B₁ up to B₅). A multipleregression analysis programme selected by stages the most relevantparameters and tested their significance. We observed that the criterion whether a dipeptide ester issweet or not, is among others defined by the L and B₅ parametersof the side chain R. Compounds are sweet provided L is confinedto certain limits (0.50 nm<L<0.62 nm), or otherwise whenL exceeds these limits, the B₅ parameter has to be greater than0.45 nm (when L<0.50 nm) or smaller than 0.72 nm (when L>0.62nm). The sweet potency defined as log S correlated very significantlywith the parameters P and B₄ (n=33, r=0.812, s=0.60, F=29.06).When two compounds, which were shown to be situated at the borderlineof the length and volume parameters, were omitted in the analysis,the correlation improved (n=31, r=0.909, s=0.40, F=42.60). Inthe latter situation we found the following equation when theintercept was set at zero: log S=0.194f + 1.472.10^–2P—3.357B₅ A previously proposed conformation of aspartame (R=CH₂-Øat the receptor site was computed in detail. We calculated thedistances of the AH-B moieties to the third binding site (thecentre of Ø) and indicated the width of the receptoraccess for this series of sweet, structurally related, dipeptidemethyl esters.