IL-33 Induces IL-9 Production in Human CD4+ T Cells and Basophils

IL-33, an IL-1 family member and ligand for the IL-1 receptor-related protein ST2, has been associated with induction of Th2 cytokines such as IL-4, IL-5, and IL-13. Here, we report that IL-33 can initiate IL-9 protein secretion in vitro in human CD4+ T cells and basophils isolated from peripheral blood. TGF-β has been described as a critical factor for IL-9 induction in Th2 cells; however, we found that TGF-β also induces co-production of IL-9 in purified, naïve (>99%) CD4⁺CD45RA⁺CD45RO⁻CD25⁻ T cells differentiated towards a Th1 profile. Subsequently, it was demonstrated that TGF-β is important, although not an absolute requirement, for IL-9 production in CD4+ T cells. IL-9 production by purified (>95%) human basophils, cultured for 24 h with IL-3 or IL-33, was found, with a strong synergy between the two, likely to be explained by the IL-3 upregulated ST2 expression. Collectively, these data indicate that barrier functioning cells are important for the regulation of IL-9 production by immune cells in inflamed tissue.     

Maltose excretion by the symbiotic Chlorella of the heliozoan Acanthocystis turfacea

Chlorella sp. strain 3.83, a symbiotic Chlorella isolated from the heliozoan Acanthocystis turfacea, excreted between 8% and 16% of assimilated ¹⁴CO₂ as maltose in the light (15000 lx), with a pH optimum around 4.8. This percentage increased when the illuminance was lowered (36% at 1700 lx). Release of [¹⁴C]maltose continued in darkness and could be inhibited by the uncoupler carbonyl cyanide p-trifluoro-methoxyphenylhydrazone and by diethylstilbestrol. Net efflux of maltose was observed even at a concentration ratio of extracellular/intracellular maltose of 7.8. Exogenous [¹⁴C]maltose (5 mM) was taken up by the cells with a rate <2% of that of simultaneous maltose release, indicating a practically unidirectional transport. It is concluded that maltose excretion is an active-transport process.Abbreviations DES diethylstilbestrol - FCCP carbonyl cyanide p-trifluoromethoxyphenyl hydrazone - p.c. packed cells This work was supported by the Deutsche Forschungsgemeinschaft. Thanks are due to Doris Meindl for skillful experimental help.     

Recent advances in imine reductase-catalyzed reactions

Imine reductases are nicotinamide-dependent enzymes that catalyze the asymmetric reduction of various imines to the corresponding amine products. Owing to the increasing roles of chiral amines and heterocyclic compounds as intermediates for pharmaceuticals, the demand for novel selective synthesis strategies is vitally important. Recent studies have demonstrated the discovery and structural characterization of a number of stereoselective imine reductase enzymes. Here, we highlight recent progress in applying imine reductases for the formation of chiral amines and heterocycles. It particularly focuses on the utilization of imine reductases in reductive aminations of aldehydes and ketones with various amine nucleophiles, one of the most powerful reactions in the synthesis of chiral amines. Second, we report on the synthesis of saturated substituted N-heterocycles by combining them with further biocatalysts, such as carboxylic acid reductases, oxidases or transaminases. Finally, we summarize the latest applications of imine reductases in the promiscuous asymmetric hydrogenation of a highly reactive carbonyl compound and the engineering of the cofactor specificity from NADPH to NADH.     

Surface characteristics of grasslands in Inner Mongolia as detected by micrometeorological measurements

A roving tower concept was used to compare a semi-arid grassland site in Inner Mongolia (China), which was fenced in 1979 and ungrazed thereafter (UG79) with differently grazed semi-arid steppe ecosystems. The study was conducted during three consecutive years characterised by contrasting precipitation. The different grazing intensities included continuously and moderately grazed (CG), winter grazed (WG), and heavily grazed (HG). Here, we compare the energy fluxes and surface parameters that characterise the differently managed plots. The main focus is on sensible heat flux (H), available energy (AE), surface temperature (T ( s )), and surface albedo (alpha). Systematic errors were excluded by a side-to-side intercomparison of the instruments, and systematic climatic differences were minimised by the close distance between the fixed and the roving eddy covariance tower. Statistically, AE and T ( s ) were always significantly different between two simultaneously measured grazing intensities. Whereas AE was higher at UG79 in all years (mean difference of about 19Wm(-2)), T ( s ) was typically lower at UG79 (mean differences of 0.4 degrees C to about 2 degrees C). The exception was the end of the vegetation period in 2004 when T ( s ) was 0.6 degrees C higher at UG79 compared to CG. At UG79 alpha was typically significantly lower, and H was typically significantly higher. Consequently, latent heat fluxes (both as energy balance residual and directly measured) do not differ much between the different grazing intensities. It is concluded, that (1) the roving tower concept is able to detect differences due to grazing, (2) differences between the sites can be attributed to real surface differences, and (3) differences due to grazing intensities are small compared to interannual differences in surface fluxes.     

Weak organic acid stress inhibits aromatic amino acid uptake by yeast, causing a strong influence of amino acid auxotrophies on the phenotypes of membrane transporter mutants.

The ability of yeasts to grow in the presence of weak organic acid preservatives is an important cause of food spoilage. Many of the determinants of acetate resistance in Saccharomyces cerevisiae differ from the determinants of resistance to the more lipophilic sorbate and benzoate. Interestingly, we show in this study that hypersensitivity to both acetate and sorbate results when the cells have auxotrophic requirements for aromatic amino acids. In tryptophan biosynthetic pathway mutants, this weak acid hypersensitivity is suppressed by supplementing the medium with high levels of tryptophan or, in the case of sorbate sensitivity, by overexpressing the Tat2p high affinity tryptophan permease. Weak acid stress therefore inhibits uptake of aromatic amino acids from the medium. This allows auxotrophic requirements for these amino acids to strongly influence the resistance phenotypes of mutant strains. This property must be taken into consideration when using these phenotypes to attribute functional assignments to genes. We show that the acetate sensitivity phenotype previously ascribed to yeast mutants lacking the Pdr12p and Azr1p plasma membrane transporters is an artefact arising from the use of trp1 mutant strains. These transporters do not confer resistance to high acetate levels and, in prototrophs, their presence is actually detrimental for this resistance.     

Cordon-bleu: a new taste in actin nucleation

Polymerization of actin filaments powers many dynamic cellular events and is directed by a small group of actin nucleators. In this issue, Ahuja et al. (2007) identify and characterize a new actin nucleator called cordon-bleu (Cobl) that may drive morphogenesis of the central nervous system during development.     

Cloning and characterization of a ribosomal protein L23a from Haemaphysalis qinghaiensis eggs by immuno screening of a cDNA expression library

A primary cDNA library with a size of 1.34 × 10⁶ PFU was constructed from Haemaphysalis qinghaiensis eggs and was immunoscreened with rabbit anti-H. qinghaiensis serum. One clone (Hq22, named following those clones obtained from adult Haemaphysalis qinghaiensis cDNA library which we constructed before) screened from the cDNA library was selected randomly for sequencing. The entire sequence of the clone was subsequently obtained using rapid amplification of the cDNA ends (RACE). A search of the cloned sequence against GenBank revealed that it related to ribosomal protein L23a (Rpl23a) and had a high percentage similarity to this protein from different species. Conserved domains for Rpl23a were also identified in the cloned sequence. Expression analysis by RT-PCR showed that this gene is expressed in salivary glands, midguts, other tissues and different developmental stages of H. qinghaiensis. Based on the H. qinghaiensis Rpl23a sequence, open reading frames (ORF) of Rpl23a of Heamaphysalis longicornis and Boophilus microplus were also cloned and were performed for comparison with Rpl23a of H. qinghaiensis and other organisms as well. Vaccine based on Rpl23a recombinant protein cannot protect sheep against H. qinghaiensis.     

Filamentous temperature-sensitive Z (FtsZ) isoforms specifically interact in the chloroplasts and in the cytosol of Physcomitrella patens

Plant filamentous temperature-sensitive Z (FtsZ) proteins have been reported to be involved in biological processes related to plastids. However, the precise functions of distinct isoforms are still elusive. Here, the intracellular localization of the FtsZ1-1 isoform in a moss, Physcomitrella patens, was examined. Furthermore, the in vivo interaction behaviour of four distinct FtsZ isoforms was investigated. Localization studies of green fluorescent protein (GFP)-tagged FtsZ1-1 and fluorescence resonance energy transfer (FRET) analyses employing all dual combinations of four FtsZ isoforms were performed in transient protoplast transformation assays. FtsZ1-1 is localized to network structures inside the chloroplasts and exerts influence on plastid division. Interactions between FtsZ isoforms occur in distinct ordered structures in the chloroplasts as well as in the cytosol. The results expand the view of the involvement of Physcomitrella FtsZ proteins in chloroplast and cell division. It is concluded that duplication and diversification of ftsZ genes during plant evolution were the main prerequisites for the successful remodelling and integration of the prokaryotic FtsZ-dependent division mechanism into the cellular machineries of distinct complex processes in plants.     

Jasmonates in arbuscular mycorrhizal interactions

The mutualistic interaction between plants and arbuscular mycorrhizal (AM) fungi is believed to be regulated from the plant side among other signals by the action of phytohormones. Evidences for this are based mainly on application experiments and determination of phytohormone levels in AM roots by comparison to non-mycorrhizal roots. In case of jasmonates, additional proof is given by reverse genetic approaches, which led to first insights into their putative role in the establishment and functioning of the symbiosis. This review summarizes the current data about phytohormone action in AM roots and the role of jasmonates in particular.     

Regulation of arbuscular mycorrhization by carbon. The symbiotic interaction cannot be improved by increased carbon availability accomplished by root-specifically enhanced invertase activity

The mutualistic interaction in arbuscular mycorrhiza (AM) is characterized by an exchange of mineral nutrients and carbon. The major benefit of AM, which is the supply of phosphate to the plant, and the stimulation of mycorrhization by low phosphate fertilization has been well studied. However, less is known about the regulatory function of carbon availability on AM formation. Here the effect of enhanced levels of hexoses in the root, the main form of carbohydrate used by the fungus, on AM formation was analyzed. Modulation of the root carbohydrate status was performed by expressing genes encoding a yeast (Saccharomyces cerevisiae)-derived invertase, which was directed to different subcellular locations. Using tobacco (Nicotiana tabacum) alcc::wINV plants, the yeast invertase was induced in the whole root system or in root parts. Despite increased hexose levels in these roots, we did not detect any effect on the colonization with Glomus intraradices analyzed by assessment of fungal structures and the level of fungus-specific palmitvaccenic acid, indicative for the fungal carbon supply, or the plant phosphate content. Roots of Medicago truncatula, transformed to express genes encoding an apoplast-, cytosol-, or vacuolar-located yeast-derived invertase, had increased hexose-to-sucrose ratios compared to beta-glucuronidase-transformed roots. However, transformations with the invertase genes did not affect mycorrhization. These data suggest the carbohydrate supply in AM cannot be improved by root-specifically increased hexose levels, implying that under normal conditions sufficient carbon is available in mycorrhizal roots. In contrast, tobacco rolC::ppa plants with defective phloem loading and tobacco pyk10::InvInh plants with decreased acid invertase activity in roots exhibited a diminished mycorrhization.