Kinetics of the Competitive Degradation of Deoxyribose and Other Molecules by Hydroxyl Radicals Produced by the Fenton Reaction in the Presence of Ascorbic Acid

The competition method in which the Fenton reaction is employed as an OH radical generator and deoxyribose as a detecting molecule, has been used to determine the rate constants for reactions of the OH radical with its scavengers. Nonlinear competition plots were obtained for those scavengers which reacted with the Fenton reagents (Fe²⁺ or H₂O₂). Ascorbic acid is believed to overcome this problem. We have investigated the kinetics of deoxyribose degradation by -OH radicals generated by the Fenton reaction in the presence of ascorbic acid, and observed that the inclusion of ascorbic acid in the Fenton system greatly increased the rate of OH radical generation. As a result, the interaction between some scavengers and the Fenton reagents became negligeable and linear competition plots of A7A vs scavenger concentrations were obtained. The effects of experimental conditions such as, the concentrations of ascorbic acid, deoxyribose, H₂O₂ and Fe²⁺-EDTA, the EDTA/Fe²⁺ ratio as well as the incubation time, on the deoxyribose degradation and the determination of the rate constant for mercaptoethanol chosen as a reference compound were studied. The small standard error, (6.76± 0.21) ±' 10⁹M^-1s^-1 observed for the rate constant values for mercaptoethanol determined under 13 different experimental conditions, indicates the latter did not influence the rate constant determination. This is in fact assured by introducing a term, k_x, into the kinetic equation. This term represents the rate of-OH reactions with other reagents such as ascorbic acid, Fe²⁺-EDTA, H₂O₂ etc. The agreement of the rate constants obtained in this work with that determined by pulse radiolysis techniques for cysteine, thiourea and many other scavengers, suggests that this simple competition method is applicable to a wide range of compounds, including those which react with the Fenton reagents and those whose solubility in water is low.     

Characterization of the quantitative trait locus OilA1 for oil content in Brassica napus

Increasing seed oil content has become one of the most important breeding criteria in rapeseed (Brassica napus). However, oil content is a complex quantitative trait. QTL mapping in a double haploid population (SG population) emerging from a cross between a German (Sollux) and Chinese (Gaoyou) cultivars revealed one QTL for oil content on linkage group A1 (OilA1), which was mapped to a 17 cM genetic interval. To further validate and characterize the OilA1, we constructed a high-resolution map using B. rapa sequence resources and developed a set of near-isogenic lines (NILs) by employing a DH line SG-DH267 as donor and Chinese parent Gaoyou as recurrent background. The results showed highly conserved synteny order between B. rapa and B. napus within the linkage group A1 and revealed a possible centromere region between two markers ZAASA1-38 and NTP3 (2.5 cM). OilA1 was firstly validated by 250 BC₅F₂ plants and was confirmed in a 10.6 cM interval between the markers ZAASA1-47 and ZAASA1-77. Further substitution mapping was conducted by using two generations of QTL-NILs, 283 lines from eight BC₅F_3:4 families and 428 plants from six BC₅F₄ sub-NILs and thus narrowed the OilA1 interval to 6.9 cM and 4.3 cM (1.4 Mb), respectively. Field investigations with two replications using homozygous BC₅F_3:4 sister sub-NILs indicated that NILs, which carry a Sollux chromosome segment across the target region showed significant higher oil content (1.26 %, p < 0.001) than their sister NILs containing Gaoyou chromosome. The OilA1 locus is of particular interest for breeding purpose in China because 80 % of Chinese cultivars do not carry this desirable allele.     

Dysbiosis Signature of Fecal Microbiota in Colorectal Cancer Patients

The human gut microbiota is a complex system that is essential to the health of the host. Increasing evidence suggests that the gut microbiota may play an important role in the pathogenesis of colorectal cancer (CRC). In this study, we used pyrosequencing of the 16S rRNA gene V3 region to characterize the fecal microbiota of 19 patients with CRC and 20 healthy control subjects. The results revealed striking differences in fecal microbial population patterns between these two groups. Partial least-squares discriminant analysis showed that 17 phylotypes closely related to Bacteroides were enriched in the gut microbiota of CRC patients, whereas nine operational taxonomic units, represented by the butyrate-producing genera Faecalibacterium and Roseburia, were significantly less abundant. A positive correlation was observed between the abundance of Bacteroides species and CRC disease status (R?=?0.462, P?=?0.046?<?0.5). In addition, 16 genera were significantly more abundant in CRC samples than in controls, including potentially pathogenic Fusobacterium and Campylobacter species at genus level. The dysbiosis of fecal microbiota, characterized by the enrichment of potential pathogens and the decrease in butyrate-producing members, may therefore represent a specific microbial signature of CRC. A greater understanding of the dynamics of the fecal microbiota may assist in the development of novel fecal microbiome-related diagnostic tools for CRC.     

Heterologous expression of cellobiohydrolase II (Cel6A) in maize endosperm

The technology of converting lignocellulose to biofuels has advanced swiftly over the past few years, and enzymes are a significant constituent of this technology. In this regard, cost effective production of cellulases has been the focus of research for many years. One approach to reach cost targets of these enzymes involves the use of plants as bio-factories. The application of this technology to plant biomass conversion for biofuels and biobased products has the potential for significantly lowering the cost of these products due to lower enzyme production costs. Cel6A, one of the two cellobiohydrolases (CBH II) produced by Hypocrea jecorina, is an exoglucanase that cleaves primarily cellobiose units from the non-reducing end of cellulose microfibrils. In this work we describe the expression of Cel6A in maize endosperm as part of the process to lower the cost of this dominant enzyme for the bioconversion process. The enzyme is active on microcrystalline cellulose as exponential microbial growth was observed in the mixture of cellulose, cellulases, yeast and Cel6A, Cel7A (endoglucanase), and Cel5A (cellobiohydrolase I) expressed in maize seeds. We quantify the amount accumulated and the activity of the enzyme. Cel6A expressed in maize endosperm was purified to homogeneity and verified using peptide mass finger printing.     

稀土元素对甜菜种子萌发,幼苗生长及块根产量的影响

本文研究了稀土元素对甜菜的生物效应。结果表明,稀土元素可显著地提高种子萌发率,促进幼苗生长,增加幼苗根系活力、叶片净光合速率与块根产量,并明显地降低了甜菜叶片细胞膜在低温下的透性,即提高了叶片的抗寒力。     

Distribution of alkaline phosphatase genes in cyanobacteria and the role of alkaline phosphatase on the acquisition of phosphorus from dissolved organic phosphorus for cyanobacterial growth

Phosphorus is a vital nutrient for cyanobacterial growth. Aside from dissolved inorganic phosphorus, dissolved organic phosphorus (DOP) is used by cyanobacterial species via the activity of alkaline phosphatase (APase), which likely plays an important role in acquiring phosphorus for algal growth in the same manner as it does in other bacteria. In this work, APase genes phoA, phoD, and phoX were found distributed in the cyanobacterial strains included in the algal genome collection of the NCBI database. PhoX has a wider distribution than the classical phoA and phoD. Furthermore, multiple types of APase genes were simultaneously identified in a single strain or genome. Anabaena flos-aquae FACHB-245 was selected as a typical strain to study the performance of cyanobacteria growing on DOP. In algal growth involving AMP or lecithin, APase regulates the release of phosphorus from DOP as confirmed by the relative quantification of phoD and phoX expression levels. Our results confirmed that the distribution of APase is prevalent in cyanobacteria and thus provides a new insight into the potential role of cyanobacterial APase on phosphorus acquisition in natural environment.     

Human placenta-derived mesenchymal stem cells loaded on linear ordered collagen scaffold improves functional recovery after completely transected spinal cord injury in canine

Traumatic spinal cord injury(SCI) is a major challenge in the clinic. In this study, we sought to examine the synergistic effects of linear ordered collagen scaffold(LOCS) and human placenta-derived mesenchymal stem cells(hPMSCs) when transplanted into completely transected beagle dogs. After 36 weeks observation, we found that LOCS+hPMSCs implants promoted better hindlimb locomotor recovery than was observed in the non-treatment(control) group and LOCS group. Histological analysis showed that the regenerated tissue after treatment was well integrated with the host tissue, and dramatically reduced the volume of cystic and chondroitin sulfate proteoglycans(CSPGs) expression. Furthermore, the LOCS+hPMSCs group also showed more neuron-specific βIII-tubulin(Tuj-1)-and NeuN-positive neurons in the lesion area, as well as axonal regeneration, remyelination and synapse formation in the lesion site. Additionally, dogs in the LOCS+hPMSCs group experienced enhanced sprouting of both ascending(CGRP-positive) sensory fibers and descending(5-HT-and TH-positive) motor fibers at the lesion area. All these data together suggested that the combined treatment had beneficial effects on neuronal regeneration and functional improvement in a canine complete transection model. Therefore, LOCS+hPMSCs implantation holds a great promise for bridging the nerve defect and may be clinically useful in the near future.     

Coexpression of the High Molecular Weight Glutenin Subunit 1Ax1 and Puroindoline Improves Dough Mixing Properties in Durum Wheat (Triticum turgidum L. ssp. durum)

Wheat end-use quality mainly derives from two interrelated characteristics: the compositions of gluten proteins and grain hardness. The composition of gluten proteins determines dough rheological properties and thus confers the unique viscoelastic property on dough. One group of gluten proteins, high molecular weight glutenin subunits (HMW-GS), plays an important role in dough functional properties. On the other hand, grain hardness, which influences the milling process of flour, is controlled by Puroindoline a (Pina) and Puroindoline b (Pinb) genes. However, little is known about the combined effects of HMW-GS and PINs on dough functional properties. In this study, we crossed a Pina-expressing transgenic line with a 1Ax1-expressing line of durum wheat and screened out lines coexpressing 1Ax1 and Pina or lines expressing either 1Ax1 or Pina. Dough mixing analysis of these lines demonstrated that expression of 1Ax1 improved both dough strength and over-mixing tolerance, while expression of PINA detrimentally affected the dough resistance to extension. In lines coexpressing 1Ax1 and Pina, faster hydration of flour during mixing was observed possibly due to the lower water absorption and damaged starch caused by PINA expression. In addition, expression of 1Ax1 appeared to compensate the detrimental effect of PINA on dough resistance to extension. Consequently, coexpression of 1Ax1 and PINA in durum wheat had combined effects on dough mixing behaviors with a better dough strength and resistance to extension than those from lines expressing either 1Ax1 or Pina. The results in our study suggest that simultaneous modulation of dough strength and grain hardness in durum wheat could significantly improve its breadmaking quality and may not even impair its pastamaking potential. Therefore, coexpression of 1Ax1 and PINA in durum wheat has useful implications for breeding durum wheat with dual functionality (for pasta and bread) and may improve the economic values of durum wheat.