Effect of seed inoculation,mycorrhizal infection and organic amendment on wheat growth

Summary The effect of seed inoculation withAzotobacter spp. orAzospirillum spp., and garbage amendment (0.5%), on the growth of wheat was studied in a field experiment under sub-tropical conditions. Two levels of N fertilizer were applied, the usual field rate (150 kg N ha^–1) and half this amount. Tillering of plants, dry matter contents and nitrogenase activity were determined 30, 60 and 90 days after sowing. At the end of the experimental period, spore numbers and percentage of mycorrhizal infection were observed in the rhizosphere and root systems of plants. Straw and grain yields were also determined. The results of this study showed that seed inoculation and/or organic amendment stimulated plant growth, nitrogenase activity and mycorrhizal infection. This was more noticeable withAzotobacter than withAzospirillum. Inoculation withAzotobacter together with 1/2 N dose and organic amendment was the most effective application (19.75 and 10.70 t ha^–1 were recorded for straw and grain yield, respectively).     

Factors affecting production and stability of the AcAFP antifungal peptide secreted by Aspergillus clavatus

We have previously reported the identification of a small, basic and cysteine-rich antifungal peptide (AcAFP) secreted by Aspergillus clavatus and shown its ability to prevent growth of various human- and plant-pathogenic filamentous fungi. In this study, we sought to determine the physiological/microbiological requirements to enhance the AcAFP production and the conditions influencing its stability. The maximum of AcAFP production was obtained when A. clavatus was grown on 2% glycerol as sole carbon source and 100 mM NaCl. The AcAFP expression was shown to be influenced by pH, being suppressed under acidic (pH 5) and strongly induced under alkaline conditions. The activity of the purified AcAFP was not affected by temperature; it loosed approximately 20% of its activity after 3 h at 100°C and was efficient through a large pH range (pH 5-12) with an optimum at pH 8. AcAFP activity decreased at high ionic strength and in the presence of 10 mM of divalent cations (Mn²⁺, Fe²⁺ and Ca²⁺).     

Physico-chemical Approach of the Amylolytic Action Pattern of a Thermostable Amylopullulanase

This paper describes the amylolytic action pattern of Thermococcus hydrothermalis recombinant amylopullulanase (Th-ApuΔ2) [E.C 3.2.1.41]. A comparison was made between amylose hydrolysis catalyzed by this enzyme and by two other amylolytic enzymes: α-amylase [E.C 3.2.1.1] (from Aspergillus oryzae) and glucoamylase [E.C. 3.2.1.3] (from Aspergillus niger), respectively taken as models for “endo” and “exo” catalytic patterns. Different independent physico-chemical methods were used to characterize the hydrolysis products obtained with the studied enzymes. Viscosity results were correlated to reducing sugars analysis to show a similarity between glucoamylase [E.C. 3.2.1.3] and Th-ApuΔ2 [E.C 3.2.1.41] behavior. On the other hand, whereas α-amylase [E.C 3.2.1.1] action rapidly decreased the viscosity of medium, glucoamylase and Th-ApuΔ2 hydrolysates have only shown a negligible reduction in viscosity. Glass transition temperatures of glucoamylase and Th-ApuΔ2 hydrolysates were found comparable (225–226°C) and significantly different from that of α-amylase (197°C). Thin-layer chromatographic analysis of hydrolysates mainly revealed the presence of glucose in the case of glucoamylase and Th-ApuΔ2 activities and in addition to glucose the Th-ApuΔ2 chromatograms have shown oligosaccharides with polymerization degree ranging from 2 to 7. These results incite us to conclude that Th-ApuΔ2 has a dual “endo” and “exo” catalytic action pattern. Analysis of the Fourier transform infrared (FTIR) results shows a comparable general aspect for all spectra. The presence of more numerous differentiated and intense peaks in the spectrum of Th-ApuΔ2 hydrolysate reveals the presence of short-chain oligosaccharides. These results confirm thin-layer chromatography results and support a dual action pattern.     

NaCl stress effects on enzymes involved in nitrogen assimilation pathway in tomato "Lycopersicon esculentum" seedlings

Tomato plants (Lycopersicon esculentum Mill, cv. Chibli F1) grown for 10 days on control medium were exposed to differing concentrations of NaCl (0, 25, 50, and 100mM). Increasing salinity led to a decrease of dry weight (DW) production and protein contents in the leaves and roots. Conversely, the root to shoot (R/S) DW ratio was increased by salinity. Na(+) and Cl(-) accumulation were correlated with a decline of K(+) and NO(3)(-) in the leaves and roots. Under salinity, the activities of nitrate reductase (NR, EC 1.6.6.1) and glutamine synthetase (GS, EC 6.3.1.2) were repressed in the leaves, while they were enhanced in the roots. Nitrite reductase (NiR, EC 1.7.7.1) activity was decreased in both the leaves and roots. Deaminating activity of glutamate dehydrogenase (GDH, EC 1.4.1.2) was inhibited, whereas the aminating function was significantly stimulated by salinity in the leaves and roots. At a high salt concentration, the nicotinamide adenine dinucleotide reduced (NADH)-GDH activity was stimulated concomitantly with the increasing NH(4)(+) contents and proteolysis activity in the leaves and roots. With respect to salt stress, the distinct sensitivity of the enzymes involved in nitrogen assimilation is discussed.     

Importance of ferric chelate reductase activity and acidification capacity in root nodules of N2-fixing common bean (Phaseolus vulgaris L.) subjected to iron deficiency

Iron is an essential nutrient for plants, especially in symbiotic N₂-fixing legumes. Although abundant in the soil, iron is generally not available to plants as it is predominantly in an insoluble form (Fe^III) . Mono- and dicotyledonous plants, except Grarnineae, have developed morphological and physiological responses, notably an increase in rhizosphere acidification (H⁺-ATPase) and an enhanced plasma membrane ferric chelate reductase activity (Fe-CR) in the roots. However, studies on the physiological responses of root nodules are lacking. The present study was initiated to investigate the acidification capacity and Fe-CR activity of nodulated roots, and intact nodules, in two contrasting common bean varieties, Coco blanc sensitive to iron deficiency and Flamingo tolerant to iron deficiency. The discovery of an induction of H⁺-ATPase and Fe-CR activities in root nodules of commonbean under iron deficiency, suggests that these organs participate in improving iron availability for the contained bacteroids.     

Megakaryoblastic leukemia factor-1 gene in the susceptibility to coronary artery disease

Coronary artery disease (CAD) is based on the atherosclerosis of coronary artery and may manifest with myocardial infarction or angina pectoris. Although it is widely accepted that genetic factors are linked to CAD and several disease-related genes have been reported, only a few could be replicated suggesting that there might be some other CAD-related genes. To identify novel susceptibility loci for CAD, we used microsatellite markers in the screening and found six different candidate CAD loci. Subsequent single nucleotide polymorphism (SNP) association studies revealed an association between CAD and megakaryoblastic leukemia factor-1 gene (MKL1). The association with a promoter SNP of MKL1, ?184C > T, was found in a Japanese population and the association was replicated in another Japanese population and a Korean population. Functional analysis of the MKL1 promoter SNP suggested that the higher MKL1 expression was associated with CAD. These findings suggest that MKL1 is involved in the pathogenesis of CAD.     

Production and optimization of thermophilic alkaline protease in solid-state fermentation by <Emphasis Type="Italic">Streptomyces</Emphasis> sp. CN902

The purpose of the present research is to study the production of thermophilic alkaline protease by a local isolate, Streptomyces sp. CN902, under solid state fermentation (SSF). Optimum SSF parameters for enzyme production have been determined. Various locally available agro-industrial residues have been screened individually or as mixtures for alkaline protease production in SSF. The combination of wheat bran (WB) with chopped date stones (CDS) (5:5) proved to be an efficient mixture for protease production as it gave the highest enzyme activity (90.50 U g⁻¹) when compared to individual WB (74.50 U g⁻¹) or CDS (69.50 U g⁻¹) substrates. This mixed solid substrate was used for the production of protease from Streptomyces sp. CN902 under SSF. Maximal protease production (220.50 U g⁻¹) was obtained with an initial moisture content of 60%, an inoculum level of 1 × 10⁸ (spore g⁻¹ substrate) when incubated at 45°C for 5 days. Supplementation of WB and CDS mixtures with yeast extract as a nitrogen source further increased protease production to 245.50 U g⁻¹ under SSF. Our data demonstrated the usefulness of solid-state fermentation in the production of alkaline protease using WB and CDS mixtures as substrate. Moreover, this approach offered significant benefits due to abundant agro-industrial substrate availability and cheaper cost.     

Enhancement of oxytetracycline production after gamma irradiation-induced mutagenesis of <Emphasis Type="Italic">Streptomyces rimosus</Emphasis> CN08 strain

Streptomyces rimosus CN08 isolated from Tunisian soil produced 8.6 mg l⁻¹ of oxytetracycline (OTC) under submerged fermentation (SmF). Attempts were made for enhancing OTC production after irradiation-induced mutagenesis of Streptomyces rimosus CN08 with Co⁶⁰-γ rays. 125 OTC-producing colonies were obtained after screening on kanamycin containing medium. One mutant called Streptomyces rimosus γ-45 whose OTC production increased 19-fold (165 mg l⁻¹) versus wild-type strain was selected. γ-45 mutant was used for OTC production under solid-state fermentation (SSF). Wheat bran (WB) was used as solid substrate and process parameters influencing OTC production were optimized. Solid-state fermentation increased the yield of antibiotic production (257 mg g⁻¹) when compared with submerged fermentation. Ammonium sulphate as additional nitrogen source enhanced OTC level to 298 mg g⁻¹. Interestingly, OTC production by γ-45 mutant was insensitive to phosphate which opens the way to high OTC production even in medium containing phosphate necessary for optimal mycelia growth.     

Antenatal presentation of Bardet-Biedl syndrome may mimic Meckel syndrome

Bardet-Biedl syndrome (BBS) is a multisystemic disorder characterized by postaxial polydactyly, progressive retinal dystrophy, obesity, hypogonadism, renal dysfunction, and learning difficulty. Other manifestations include diabetes mellitus, heart disease, hepatic fibrosis, and neurological features. The condition is genetically heterogeneous, and eight genes (BBS1-BBS8) have been identified to date. A mutation of the BBS1 gene on chromosome 11q13 is observed in 30%-40% of BBS cases. In addition, a complex triallelic inheritance has been established in this disorder--that is, in some families, three mutations at two BBS loci are necessary for the disease to be expressed. The clinical features of BBS that can be observed at birth are polydactyly, kidney anomaly, hepatic fibrosis, and genital and heart malformations. Interestingly, polydactyly, cystic kidneys, and liver anomalies (hepatic fibrosis with bile-duct proliferation) are also observed in Meckel syndrome, along with occipital encephalocele. Therefore, we decided to sequence the eight BBS genes in a series of 13 antenatal cases presenting with cystic kidneys and polydactyly and/or hepatic fibrosis but no encephalocele. These fetuses were mostly diagnosed as having Meckel or "Meckel-like" syndrome. In six cases, we identified a recessive mutation in a BBS gene (three in BBS2, two in BBS4, and one in BBS6). We found a heterozygous BBS6 mutation in three additional cases. No BBS1, BBS3, BBS5, BBS7, or BBS8 mutations were identified in our series. These results suggest that the antenatal presentation of BBS may mimic Meckel syndrome.