Laboratory and greenhouse evaluation of a new entomopathogenic strain of Beauveria bassiana for control of the onion thrips Thrips tabaci

Abstract

The onion thrips Thrips tabaci is one of the most important pests of greenhouse and open-field broccoli, onion and other crops. However, the current strategy of using synthetic pesticides for its control is inadequate and unsustainable, leading to a growing interest in novel and effective biological control alternatives such as entomopathogenic fungi. Among 20 isolates of Beauveria bassiana tested for virulence against T. tabaci in laboratory bioassays, we found strain SZ-26 as the most potent, causing 83–100% mortality in adults at 1×10⁷ mL^?1conidia after 4–7 days. Further experiments in greenhouses showed the strain SZ-26 significantly lowered the numbers of adult and larval stages.     

Genome-wide identification and expression profiling of ankyrin-repeat gene family in maize

Members of the ankyrin repeats (ANK) gene family encode ANK domain that are common in diverse organisms and play important roles in cell growth and development, such as cell-cell signal transduction and cell cycle regulation. Recently, genome-wide identification and evolutionary analyses of the ANK gene family have been carried out in Arabidopsis and rice. However, little is known regarding the ANK genes in the entire maize genome. In this study, we described the identification and structural characterization of 71 ANK genes in maize (ZmANK). Then, comprehensive bioinformatics analyses of ZmANK genes family were performed including phylogenetic, domain and motif analysis, chromosomal localization, intron/exon structural patterns, gene duplications and expression profiling. Domain composition analyses showed that ZmANK genes formed ten subfamilies. Five tandem duplications and 14 segmental duplications were identified in ZmANK genes. Furthermore, we took comparative analysis of the total ANK gene family in Arabidopsis, rice and maize, ZmANKs were more closely paired with OsANKs than with AtANKs. At last, expression profile analyses were performed. Forty-one members of ZmANK genes held EST sequences records. Semi-quantitative expression and microarray data analysis of these 41 ZmANK genes demonstrated that ZmANK genes exhibit a various expression pattern, suggesting that functional diversification of ZmANK genes family. The results will present significant insights to explore ANK genes expression and function in future studies in maize.     

Genetic analysis of Agrobacterium tumefaciens unipolar polysaccharide production reveals complex integrated control of the motile‐to‐sessile switch

Many bacteria colonize surfaces and transition to a sessile mode of growth. The plant pathogen Agrobacterium tumefaciens produces a u nip olar p olysaccharide (UPP) adhesin at single cell poles that contact surfaces. Here we report that elevated levels of the intracellular signal cyclic diguanosine monophosphate (c‐di‐GMP) lead to surface‐contact‐independent UPP production and a red colony phenotype due to production of UPP and the exopolysaccharide cellulose, when A. tumefaciens is incubated with the polysaccharide stain Congo Red. Transposon mutations with elevated Congo Red staining identified presumptive UPP‐negative regulators, mutants for which were hyperadherent, producing UPP irrespective of surface contact. Multiple independent mutations were obtained in visN and visR, activators of flagellar motility in A. tumefaciens, now found to inhibit UPP and cellulose production. Expression analysis in a visR mutant and isolation of suppressor mutations, identified three diguanylate cyclases inhibited by VisR. Null mutations for two of these genes decrease attachment and UPP production, but do not alter cellular c‐di‐GMP levels. However, analysis of catalytic site mutants revealed their GGDEF motifs are required to increase UPP production and surface attachment. Mutations in a specific presumptive c‐di‐GMP phosphodiesterase also elevate UPP production and attachment, consistent with c‐di‐GMP activation of surface‐dependent adhesin deployment.     

Sequence‐independent processing site of the C‐terminal domain (CTD) influences maturation of the RgpB protease from Porphyromonas gingivalis

The Gram‐negative periodontal pathogen Porphyromonas gingivalis produces a family of outer membrane‐anchored proteases, the gingipains, shown to play an essential role in virulence of the organism. The C‐terminal domain (CTD) of gingipains and other secreted proteins is known to be the targeting signal for maturation and translocation of the protein through the outer membrane. The CTD is subsequently cleaved during the secretion process. Multiple alignment of various CTDs failed to define a consensus sequence at the putative CTD processing site. Using mutagenesis, we were able to show that cleavage at the site is not dependent on a specific residue and that recognition of the site is independent of local sequence. Interestingly, length of the junction between the CTD and adjacent Ig‐like subdomain has a critical influence on post‐translational glycan modification of the protein, whereby insertion of additional residues immediately N‐terminal to the cleavage site results in failure of glycan modification and release of soluble protease into the culture medium. Various hypotheses are presented to explain these phenomena. Knowledge of the role CTDs play in maturation of gingipains has broader application for understanding maturation of CTD homologues expressed by bacteria of the Bacteriodetes phylum.     

Biodegradation of high concentration of nitrobenzene by Pseudomonas corrugata embedded in peat-phosphate esterified polyvinyl alcohol

Efficiency on biodegradation of high concentration of nitrobenzene (NB) by peat-phosphate esterified polyvinyl alcohol-embedded NB-degrading bacteria Pseudomonas corrugata was conducted compared to free bacteria cells. Its biodegradation kinetics, reuse ability, degradation effect in the absence of the essential element needed for the growth of bacteria and degradation efficiency of the raw water from the contaminated site were also invested. Results show that the degradation rate when the concentration of NB was at 600, 750, and 900 mg/L reached 91.02, 83.23, and 55.9 %, which was higher than that observed in free bacteria at the same concentration levels. Biodegradation kinetics of the material could be well described by first- and zero-order kinetics when the concentration of NB was at 300, 450 mg/L and 600, 750, 900 mg/L, respectively. Stable degradation activity (stayed at a level of approximately 70 %) was displayed during the 11th repeat-batch experiment. The affect of absence of phosphorus in the medium can be abated ascribed to the addition of peat, which contributes with organic matter and other elements such as nitrogen and phosphorus necessary to maintain metabolically active the microorganisms. Effective biodegradation of the raw water from the experimental site revealed that the material can be a potential candidate for treating NB-contaminated wastewater in the practical setting.     

Use of β-galactosidase liposome model as a novel method to screen freeze-drying cryoprotectants

This study developed a novel method of screening cryoprotectants used to improve the survivability of lyophilized Lactobacillus helveticus. To develop a liposome encapsulated β-galactosidase (β-gal) as a cell membrane model, the β-gal liposome was characterized in terms of mean size, poly dispersity index, zeta potential, along with transmission electron microscopy. 800 W of ultrasonic power and 10 min of sonication time were the optimal experimental conditions to obtain the desirable β-gal liposome. Subsequently, different cryoprotectants were mixed with the β-gal liposome during freeze-drying. After freeze-drying, liposomes were hydrolized, and the protective effect of cryoprotectants was assessed as the release rate of encapsulated β-gal. The lowest release rate of β-gal was obtained using 10 mg/100 ml trehalose and 0.2 mg/100 ml hyaluronic acid.     

PEGylation-aided refolding of globular adiponectin

Globular adiponectin (GAD) as the active domain of adiponectin is a promising candidate for anti-diabetic drug development. The recombinant production of GAD in Escherichia coli, however, is difficult because it is mainly expressed as inclusion bodies which need to be refolded to regain function. In this study we developed a novel method for refolding of GAD with a high efficiency by using polyethylene glycol (PEG) conjugation. An artificially designed DNA sequence encoding for GAD was synthesized and inserted into the pET28a vector to construct an expression plasmid which was thereafter transformed into E. coli BL21 (DE3) host cells for heterologous expression. After bacterial cell culture employing auto-induction medium, the inclusion bodies were collected, washed and dissolved in guanidine hydrochloride before PEG conjugation. Then the PEG-conjugated GAD was refolded by dialysis and purified by two steps of chromatography. The refolded conjugate showed a marked glucose-lowering activity in mice, demonstrating that it had been successfully refolded. As a convenient method, PEGylation-aided refolding could also be tested on other proteins to explore its suitability.     

Biomass production, relative competitive ability and water use efficiency of two dominant species in semiarid Loess Plateau under different water supply and fertilization treatments

Water stress and nutrient deficiency are considered to be the main environmental factors limiting plant growth and species interaction in semiarid regions. However, less is known about the interactive effects of soil water, nitrogen and phosphorus on native species growth and relative competitive ability. A replacement series design method was used with 12 mixed plants of Bothriochloa ischaemum and Lespedeza davurica grown in a pot experiment under three water regimes and four fertility treatments. Intercropping systems were assessed on the basis of indices such as biomass production and allocation, relative competitive ability, aggressivity, relative yield total and water use efficiency (WUE). Water stress decreased significantly the total biomass production for each species, either in monoculture or in mixtures. N, P, or NP application can significantly improve biomass production of the two species in their mixtures. There was no obvious change trend in root/shoot ratio of B. ischaemum or L. davurica in different mixture proportions. Relative yield total (RYT) values ranged from 0.98 to 1.39. Aggressivity values of B. ischaemum to L. davurica were positive in all water regimes and fertilizations, implying that B. ischaemum was the dominant species. Relative competition intensity values of B. ischaemum (i.e., RCI_B) were less than zero, while greater than zero for L. davurica (i.e., RCI_L), indicating that the effects of intraspecific competition with L. davurica were stronger for B. ischaemum, and the opposite for L. davurica. WUE increased gradually as the proportion of B. ischaemum increased in mixtures, and a 10:2 B. ischaemum:L. davurica mixture proportion had significantly higher WUE. Results suggest that it is advantageous to grow the two species together to maximize biomass production and the recommended mixture ratio was 10:2 of B. ischaemum to L. davurica because it gave higher RYT and significantly higher WUE under conditions of water deficit.     

Promotion or suppression of glucose isomerization in subcritical aqueous straight- and branched-chain alcohols

The influence of water-miscible alcohols (methanol, 1-propanol, 2-propanol, and t-butyl alcohol) on the isomerization of glucose to fructose and mannose was investigated under subcritical aqueous conditions (180–200 °C). Primary and secondary alcohols promoted the conversion and isomerization of glucose to afford fructose and mannose with high and low selectivity, respectively. On the other hand, the decomposition (side-reaction) of glucose was suppressed in the presence of the primary and secondary alcohols compared with that in subcritical water. The yield of fructose increased with increasing concentration of the primary and secondary alcohols, and the species of the primary and secondary alcohols tested had little effect on the isomerization behavior of glucose. In contrast, the isomerization of glucose was suppressed in subcritical aqueous t-butyl alcohol. Both the conversion of glucose and the yield of fructose decreased with increasing concentration of t-butyl alcohol. In addition, mannose was not detected in reactions using subcritical aqueous t-butyl alcohol.     

Extraction of crude polysaccharides from Duchesnea indica (Andrews) Focke: optimization by response surface methodology

A full set of optimization procedure was applied to the extraction of anti-viral polysaccharides from Duchesnea indica (Andrews) Focke. By Plackett–Burman factorial design, three parameters (extraction time, extraction temperature, and ratio of water to raw material) were identified as significant to the extraction yield. However, no significant parameters had been identified for antiviral activity. A three-level-three-factor Box–Behnken factorial design was then employed to further optimize the extraction condition. The experimental data were fitted to a second-order polynomial equation using multiple regression analysis and also examined using appropriate statistical methods. This led to the construction of a response surface indicating the optimal values for each parameter and response studied. Concerning the extraction yield, an extraction at 98.51?ºC for 6.16 h with a ratio of water to raw material of 30.94 mL/g was found to be optimal. Under the optimized conditions, the experimental yield was 6.430 ± 0.078%, which was well matched with the predicted yield of 6.509%.