Ensifer mexicanus sp. nov. a new species nodulating Acacia angustissima (Mill.) Kuntze in Mexico

A new lineage of Ensifer nodulating the American legume Acacia angustissima in the tropical forest of Chiapas and Morelos, Mexico is described. Bacteria were identified as Ensifer with ssb or nolR specific primers. Phylogenetic analysis with partial sequences of the five chromosomal genes gyrA, nolR, recA, rpoB and rrs revealed that this new lineage is related to African Ensifer terangae. The results of total DNA-DNA hybridization and selected phenotypic tests among the A. angustissima strains and E. terangae indicated that they belong to different species. The phylogeny with the symbiotic nifH gene also separates this group as a different clade but with close affinities to bacteria belonging to the genus Ensifer isolated from American hosts. ITTG R7(T) (=CFN ER1001, HAMBI 2910, CIP 109033, ATCC BAA-1312, DSM18446) is the type strain of a new species for which the name Ensifer mexicanus sp. nov. is proposed.     

Role of Reactive Oxygen Species in the Initiation of Plant Retrograde Signaling

The interaction between the nucleus and the different organelles is important in the physiology of the plant. Reactive oxygen species (ROS) are a by-product of the oxidation of organic molecules to obtain energy by the need to carry out the electron transfer between the different enzymatic complexes. However, they also have a role in the generation of what is known as retrograde signaling. This signal comes from the different organelles in which the oxidation of molecules or the electron transference is taking place such as mitochondria and chloroplasts. Furthermore, ROS can also induce the release of signals from the apoplast. It seems that these signals plays a role communicating to the nucleus the current status of the different parts of the plant cell to induce a changes in gene expression. In this review, the molecular mechanism of ROS retrograde signaling is described.

     

Arsenic species uptake and translocation in Elodea canadensis

Abstract

The capacity of Elodea canadensis to phytofiltrate arsenic species from water was evaluated. Plants were adapted to tap water and supplemented with 15 and 250?µg L^?1 of As. Inorganic arsenic species (As III, As V), and organic arsenic compounds: monomethylarsonate (MMA) and dimethylarsinate (DMA) were analyzed. Sampling was carried out at different times after exposure in culture water and plant organs. Plants exposed to 15?µg L^?1 of As concentration showed no significant difference on As concentration (95% confidence level) in their organs compared to controls. When plants were exposed to 250?µg L^?1 of As concentration, a significant increase of As concentration in plant organs was observed. After 1?h exposure, plants reduce 63.16% the As concentration in the culture water, with a bioaccumulation factor (BF) of 4.3. Under these conditions, E. canadensis accumulate As V in roots and do not translocate it to stems (transfer factor <1). MMA was determined in stems and leaves. E. canadensis effectively phytofiltrate As from tap water of a city located in an arsenic endemic area from concentrations of 36?µg L^?1 to undetectable levels (10?ng L^?1).     

CRISP1 as a novel CatSper regulator that modulates sperm motility and orientation during fertilization

Ca²⁺-dependent mechanisms are critical for successful completion of fertilization. Here, we demonstrate that CRISP1, a sperm protein involved in mammalian fertilization, is also present in the female gamete and capable of modulating key sperm Ca²⁺ channels. Specifically, we show that CRISP1 is expressed by the cumulus cells that surround the egg and that fertilization of cumulus–oocyte complexes from CRISP1 knockout females is impaired because of a failure of sperm to penetrate the cumulus. We provide evidence that CRISP1 stimulates sperm orientation by modulating sperm hyperactivation, a vigorous motility required for penetration of the egg vestments. Moreover, patch clamping of sperm revealed that CRISP1 has the ability to regulate CatSper, the principal sperm Ca²⁺ channel involved in hyperactivation and essential for fertility. Given the critical role of Ca²⁺ for sperm motility, we propose a novel CRISP1-mediated fine-tuning mechanism to regulate sperm hyperactivation and orientation for successful penetration of the cumulus during fertilization.     

Ant pollination promotes spatial genetic structure in the long‐lived plant Borderea pyrenaica (Dioscoreaceae)

Plant survival in alpine habitats is controlled, in several cases, by pollination and seed dispersal success. We have investigated the genetic structure and mating patterns of the endangered Borderea pyrenaica (Dioscoreaceae), one of the oldest herbaceous Pyrenean mountain plants. Simple sequence repeat‐based genotyping was carried out on all the reproductive female and male individuals and in all the female‐descendent progenies of a population of this plant. Although the offspring sampling (246) was twice the size of the adult sampling (122), the latter group showed higher levels of heterozygosity and approximately 20% more alleles than the offspring. Probabilistic spatial neighbourhood modelling of parentage analysis, based on the exponential‐power type model, showed immigration rates of pollen at 63.3%. The present study also detected a strong spatial clustering; most of the sired seeds of B. pyrenaica (68.83%) occurred at distances of up to 20 m, whereas kinship coefficients of adult plants reached zero at spatial distances (d) < 5 m, and 5 < d < 10 m for females and males, respectively. These results support the hypothesis of a terrestrial ant‐mediated, rather than a flying insect‐mediated pollination in B. pyrenaica.     

Denatured state aggregation parameters derived from concentration dependence of protein stability

Protein aggregation is a major issue affecting the long-term stability of protein preparations. Proteins exist in equilibrium between the native and denatured or partially denatured conformations. Often denatured or partially denatured conformations are prone to aggregate because they expose to solvent the hydrophobic core of the protein. The aggregation of denatured protein gradually shifts the protein equilibrium toward increasing amounts of denatured and ultimately aggregated protein. Recognizing and quantitating the presence of denatured protein and its aggregation at the earliest possible time will bring enormous benefits to the identification and selection of optimal solvent conditions or the engineering of proteins with the best stability/aggregation profile. In this article, a new approach that allows simultaneous determination of structural stability and the amount of denatured and aggregated protein is presented. This approach is based on the analysis of the concentration dependence of the Gibbs energy (ΔG) of protein stability. It is shown that three important quantities can be evaluated simultaneously: (i) the population of denatured protein, (ii) the population of aggregated protein, and (iii) the fraction of denatured protein that is aggregated.     

Characterization and Pathogenicity of Colletotrichum gloeosporioides and C. karstii Causing Preharvest Disease on Citrus sinensis in Italy

During the period from 2010 to 2013 preharvest symptoms were detected on different cultivars of sweet orange in six orchards in Catania, Siracusa and Enna provinces, Southern Italy. A total of 56 monosporic fungal isolates were obtained, and among these, 44 were identified as Colletotrichum gloeosporioides and 12 as C. karstii through morphological and molecular analysis. PCR with primers ITS1 and ITS4, primers TubGF1 and TubGR specific for β‐tubulin gene, primers GDF‐GDR, specific for Glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) gene, were used to confirm the identification of Colletotrichum isolates from citrus. The ITS1‐5.8S‐ITS2 region, a portion of approximately 500 bp of β‐tubulin gene and a fragment of 220 bp of GAPDH gene of the isolates were sequenced and analysed with the BLASTn program. Koch's postulates were fulfilled by pathogenicity tests carried out on fruit of ‘Tarocco Scirè’ and ‘Tarocco Nucellare’ with representative isolates of C. gloeosporioides and C. karstii. Field surveys and pathogenicity tests revealed significant differences in fruit susceptibility between ‘Tarocco Scirè’ and ‘Tarocco Nucellare’ and in virulence between the fungal species. To our knowledge, this is the first report on the emergence of Colletotrichum spp. causing anthracnose in preharvest conditions.     

Intrinsic Levanase Activity of Bacillus subtilis 168 Levansucrase (SacB)

Levansucrase catalyzes the synthesis of fructose polymers through the transfer of fructosyl units from sucrose to a growing fructan chain. Levanase activity of Bacillus subtilis levansucrase has been described since the very first publications dealing with the mechanism of levan synthesis. However, there is a lack of qualitative and quantitative evidence regarding the importance of the intrinsic levan hydrolysis of B. subtilis levansucrase and its role in the levan synthesis process. Particularly, little attention has been paid to the long-term hydrolysis products, including its participation in the final levan molecules distribution. Here, we explored the hydrolytic and transferase activity of the B. subtilis levansucrase (SacB) when levans produced by the same enzyme are used as substrate. We found that levan is hydrolyzed through a first order exo-type mechanism, which is limited to a conversion extent of around 30% when all polymer molecules reach a structure no longer suitable to SacB hydrolysis. To characterize the reaction, Isothermal Titration Calorimetry (ITC) was employed and the evolution of the hydrolysis products profile followed by HPLC, GPC and HPAEC-PAD. The ITC measurements revealed a second step, taking place at the end of the reaction, most probably resulting from disproportionation of accumulated fructo-oligosaccharides. As levanase, levansucrase may use levan as substrate and, through a fructosyl-enzyme complex, behave as a hydrolytic enzyme or as a transferase, as demonstrated when glucose and fructose are added as acceptors. These reactions result in a wide variety of oligosaccharides that are also suitable acceptors for fructo-oligosaccharide synthesis. Moreover, we demonstrate that SacB in the presence of levan and glucose, through blastose and sucrose synthesis, results in the same fructooligosaccharides profile as that observed in sucrose reactions. We conclude that SacB has an intrinsic levanase activity that contributes to the final levan profile in reactions with sucrose as substrate.