Increased demand for NAD+ relative to ATP drives aerobic glycolysis

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Azide-resistant mutants in Acinetobacter calcoaceticus A2 are defective in protein secretion

Abstract Azide, an inhibitor of ATPase, and a specific inhibitor of protein export was used in order to select for protein secretion mutants in Acinetobacter calcoaceticus A2. Two such mutants were isolated that were azide-resistant and defective in the general protein transport system. The mutation also conferred additional phenotypic changes, including an inability to grow on minimal media or at 40°C. The existence of protein secretion mutants with a selectable phenotype may be useful for the genetic study of protein export.     

chs-4, a class IV chitin synthase gene fromNeurospora crassa

InSaccharomyces cerevisiae, most of the cellular chitin is produced by chitin synthase III, which requires the product encoded by theCSD2/CAL1/DIT101/KT12 gene. We have identified, isolated and structurally characterized aCSD2/CAL1/DIT101/KT12 homologue in the filamentous ascomyceteNeurospora crassa and have used a reverse genetics approach to determine its role in vivo. The yeast gene was used as a heterologous probe for the isolation of aN. crassa gene (designatedchs-4) encoding a polypeptide belonging to a class of chitin synthases which we have designated class IV. The predicted polypeptide encoded by this gene is highly similar to those ofS. cerevisiae andCandida albicans. N. crassa strains in whichchs-4 had been inactivated by the Repeat-Induced Point mutation (RIP) process grew and developed in a normal manner under standard growth conditions. However, when grown in the presence of sorbose (a carbon source which induces morphological changes accompanied by elevated chitin content), chitin levels in thechs-4 ^RIP strain were significantly lower than those observed in the wild type. We suggest that CHS4 may serve as an auxiliary enzyme inN. crassa and that, in contrast to yeasts, it is possible that filamentous fungi may have more than one class IV chitin synthase.A. Beth Din and C. A. Specht contributed equally to this work     

Comparison of debrisoquine and guanethidine in treatment of hypertension.

A cross-over trail of debrisoquine and guanethidine in 32 patients showed that both drugs were equally effective in lowering both systolic and diastolic blood pressure. The degree to which they were tolerated by the patients, however, differed greatly. After three months on each drug 18 patients preferred debrisoquine, nine preferred guanethidine, and five showed no particular preference. At current prices the cost of daily treatment to the patient was cheaper with debrisoquine than with guanethidine.     

Wide vessels sustain marginal transpiration flux and do not optimize inefficient gas exchange activity under impaired hydraulic control and salinity

Plants optimize water use and carbon assimilation via transient regulation of stomata resistance and by limiting hydraulic conductivity in a long-term response of xylem anatomy. We postulated that without effective hydraulic regulation plants would permanently restrain water loss and photosynthetic productivity under salt stress conditions. We compared wild-type tomatoes to a transgenic type (TT) with impaired stomatal control. Gas exchange activity, biomass, starch content, leaf area and root traits, mineral composition and main stems xylem anatomy and hydraulic conductivity were analyzed in plants exposed to salinities of 1 and 4 dS m⁻¹ over 60 days. As the xylem cannot easily readjust to different environmental conditions, shifts in its anatomy and the permanent effect on plant hydraulic conductivity kept transpiration at lower levels under unstressed conditions and maintained it under salt-stress, while sustaining higher but inefficient assimilation rates, leading to starch accumulation and decreased plant biomass, leaf and root area and root length. Narrow conduits in unstressed TT plants were related to permanent restrain of hydraulic conductivity and plant transpiration. Under salinity, TT plants followed the atmospheric water demand, sustained similar transpiration rate from unstressed to salt-stressed conditions and possibly maintained hydraulic integrity, due to likely impaired hydraulic regulation, wider conduits and higher hydraulic conductivity. The accumulation of salts and starch in the TT plants was a strong evidence of salinity tolerance via osmotic regulation, also thought to help to maintain the assimilation rates and transpiration flux under salinity, although it was not translated into higher growth.     

MEKK2 Kinase Association with 14-3-3 Protein Regulates Activation of c-Jun N-terminal Kinase

MEKK2 (MAP/ERK kinase kinase-2) is a serine/threonine kinase that belongs to the MEKK/STE11 family of MAP kinase kinase kinases (MAP(3)Ks). MEKK2 integrates stress and mitogenic signals to the activation of NF-κB, JNK1/2, p38, and ERK5 pathways. We have found that MEKK2 is regulated through a phosphorylation-dependent association with 14-3-3, a group of adapters that modulate dimerization and association between proteins. We found that MEKK2 was phosphorylated at Thr-283, which resulted in decreased activation loop phosphorylation at Ser-519 and consequently reduced activity. Mechanistically, we found that MEKK2 associated with inactive MEKK2 in the absence of 14-3-3 binding, which led to trans-autophosphorylation of Ser-519. Enforced binding with 14-3-3 reduced Ser-519 trans-autophosphorylation. Expression of T283A MEKK2 within a MEKK2^−/− background enhanced stress-activated c-Jun N-terminal kinase activity while elevating IL-6 expression, but also reduced ERK activation with a corresponding reduced proliferation rate. These results indicate that Thr-283 phosphorylation is an important regulatory mechanism for MEKK2 activation.