Screening for hetero-transglycosylating activities in extracts from nasturtium (Tropaeolum majus)

Using combinations of different polysaccharides as glycosyl donors and of oligosaccharides fluorescently labeled by sulforhodamine (SR) as glycosyl acceptors, we screened for the presence of transglycosylating activities in extracts from nasturtium (Tropaeolum majus). Besides xyloglucan endotransglycosylase/hydrolase (XTH/XET, EC 2.4.1.207) activity, which transfers xyloglucanosyl residues from xyloglucan (XG) to XG-derived oligosaccharides (XGOs), a glycosyl transfer from XG to SR-labeled cellooligosaccharides and laminarioligosaccharides has been detected. The XGOs also served as acceptors for the glycosyl transfer from soluble cellulose derivatives carboxymethyl cellulose and hydroxyethylcellulose. The effectivity of these polysaccharides as glycosyl donors for transfer to XG-derived octasaccharide [1-3H]XXLGol decreased in the order XG > HEC > CMC. Isoelectric focusing in polyacrylamide gels showed that bands corresponding to hetero-transglycosylase activities coincided with zones corresponding to XTH/XET. These results can be explained as due either to substrate non-specificity of certain isoenzymes of XTH/XET or to existence of enzymes catalyzing a hetero-transfer, that is the formation of covalent linkages between different types of carbohydrate polymers.     

Enhancement of chilling resistance of inoculated grapevine plantlets with a plant growth-promoting rhizobacterium, Burkholderia phytofirmans strain PsJN

In vitro inoculation of Vitis vinifera L. cv. Chardonnay explants with a plant growth-promoting rhizobacterium, Burkholderia phytofirmans strain PsJN, increased grapevine growth and physiological activity at a low temperature. There was a relationship between endophytic bacterial colonization of the grapevine plantlets and their growth at both ambient (26 degrees C) and low (4 degrees C) temperatures and their sensitivities to chilling. The major benefits of bacterization were observed on root growth (11.8- and 10.7-fold increases at 26 degrees C and 4 degrees C, respectively) and plantlet biomass (6- and 2.2-fold increases at 26 degrees C and 4 degrees C, respectively). The inoculation with PsJN also significantly improved plantlet cold tolerance compared to that of the nonbacterized control. In nonchilled plantlets, bacterization enhanced CO(2) fixation and O(2) evolution 1.3 and 2.2 times, respectively. The nonbacterized controls were more sensitive to exposure to low temperatures than were the bacterized plantlets, as indicated by several measured parameters. Moreover, relative to the noninoculated controls, bacterized plantlets had significantly increased levels of starch, proline, and phenolics. These increases correlated with the enhancement of cold tolerance of the grapevine plantlets. In summary, B. phytofirmans strain PsJN inoculation stimulates grapevine growth and improves its ability to withstand cold stress.     

Inhibition of photosystem II photochemistry by Cr is caused by the alteration of both D1 protein and oxygen evolving complex

The effect of chromium (Cr) on photosystem II (PSII) electron transport and the change of proteins content within PSII complex were investigated. When Lemna gibba was exposed to Cr during 96 h, growth inhibition was found to be associated with an alteration of the PSII electron transport at both PSII oxidizing and reducing sides. Investigation of fluorescence yields at transients K, J, I, and P suggested for Cr inhibitory effect to be located at the oxygen-evolving complex and Q_A reduction. Those Cr-inhibitory effects were related to the change of the turnover of PSII D1 protein and the alteration of 24 and 33 kDa proteins of the oxygen-evolving complex. The inhibition of the PSII electron transport and the formation of reactive oxygen species induced by Cr were highly correlated with the decrease in the content of D1 protein and the amount of 24 and 33 kDa proteins. Therefore, functional alteration of PSII activity by Cr was closely related with the structural change within PSII complex.     

One-pot synthesis of antiviral acyclovir and other nucleosides derivatives using doped natural phosphate as lewis acid catalyst

Natural phosphate doped with iodine or potassium iodide is an active catalyst for the one-pot synthesis of acyclonucleosides. To demonstrate the utility of the new catalyst system, the highly important antiviral drug acyclovir was directly and regioselectively obtained from NAcG with no byproducts.     

<Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> and Its Probiotic and Food Potentialities

The number of studies claiming probiotic health effects of Lactobacillus plantarum is escalating. Lb. plantarum is a lactic acid bacterium found in diverse ecological niches, highlighting its particular capabilities of adaptation and genome plasticity. Another function that needs to be underlined is the capabilities of Lb. plantarum to produce diverse and potent bacteriocins, which are antimicrobial peptides with possible applications as food preservative or antibiotic complementary agents. Taken together, all these characteristics design Lb. plantarum as a genuine model for academic research and viable biological agent with promising applications. The present review aims at shedding light on the safety of Lb. plantarum and run through the main studies underpinning its beneficial claims. The mechanisms explaining probiotic-related features are discussed.     

Membrane dynamics and cell polarity: the role of sphingolipids

In recent years, glycosphingolipids (GSLs) have attracted widespread attention due to the appreciation that this class of lipids has a major impact on biological life. Inhibition of the synthesis of glucosylceramide, which serves as a precursor for the generation of complex glycosphinglipids, is embryonic lethal. GSLs play a major role in growth and development. Metabolites of sphingolipids, such as ceramide, sphinganine, and sphingosine, may function as second messengers or regulators of signal transduction that affect events ranging from apoptosis to the (co)regulation of the cell cycle. In addition, GSLs can provide a molecular platform for clustering of signal transducers. The ability of sphingolipids, with or without cholesterol, to form microdomains or rafts is critical in sorting and membrane transport that underlies the biogenesis of polarized membrane domains. Here, a brief summary is presented of some recent developments in this field, with a particular emphasis on raft assembly and membrane transport in the establishment of membrane polarity.     

Synthesis of new homo and heterodimers of 2',3'-dideoxyinosine (ddI) using ester linkages

A series of new homo and heterodimers of ddI has been synthesized. A glutarate diester spacer was used to covalently couple ddI onto ddI, AZT or d4T.     

North African hybrid sparrows (Passer domesticus,P. hispaniolensis) back from oblivion – ecological segregation and asymmetric mitochondrial introgression between parental species

A stabilized hybrid form of the house sparrow (Passer domesticus) and the Spanish sparrow (P. hispaniolensis) is known as Passer italiae from the Italian Peninsula and a few Mediterranean islands. The growing attention for the Italian hybrid sparrow and increasing knowledge on its biology and genetic constitution greatly contrast the complete lack of knowledge of the long‐known phenotypical hybrid sparrow populations from North Africa. Our study provides new data on the breeding biology and variation of mitochondrial DNA in three Algerian populations of house sparrows, Spanish sparrows, and phenotypical hybrids. In two field seasons, the two species occupied different breeding habitats: Spanish sparrows were only found in rural areas outside the cities and bred in open‐cup nests built in large jujube bushes. In contrast, house sparrows bred only in the town centers and occupied nesting holes in walls of buildings. Phenotypical hybrids were always associated with house sparrow populations. House sparrows and phenotypical hybrids started breeding mid of March, and most pairs had three successive clutches, whereas Spanish sparrows started breeding almost one month later and had only two successive clutches. Mitochondrial introgression is strongly asymmetric because about 75% of the rural Spanish sparrow population carried house sparrow haplotypes. In contrast, populations of the Italian hybrid form, P. italiae, were genetically least diverse among all study populations and showed a near‐fixation of house sparrow haplotypes that elsewhere were extremely rare or that were even unique for the Italian Peninsula. Such differences between mitochondrial gene pools of Italian and North African hybrid sparrow populations provide first evidence that different demographic histories have shaped the extant genetic diversity observed on both continents.