玉米粗缩病毒基因组第七组份的cDNA克隆及序列分析

从采自中国河北滦城感病的玉米材料中提取玉米粗缩病毒(MRDV)的双链RNA。根据已知MRDV的部分序列设计引物,反转录、PCR扩增,克隆并测序分析了MRDV的第七片段(S7)cDNA序列。结果表明,S7 cDNA序列全长为1936bp,与国外所测的MRDV S7的序列长度相等,而且S7包含的两个阅读框(ORF1和ORF2)位置无变化。它们的核苷酸和最大开放阅读框(ORF1)同源性分别为877%和91.6%,然而,MRDV S7的片段与水稻黑条矮缩病毒(RBSDV)S8片段的核苷酸和最大开放阅读框(ORF1)有更高的同源性,分别为95.5%和93.5%。     

Bioethanol production from ammonia percolated wheat straw

This study examined the effectiveness of ammonia percolation pretreatment of wheat straw for ethanol production. Ground wheat straw at a 10% (w/v) loading was pretreated with a 15% (v/v) ammonia solution. The experiments were performed at treatment temperature of 50∼170°C and residence time of 10∼150 min. The solids treated with the ammonia solution showed high lignin degradation and sugar availability. The pretreated wheat straw was hydrolyzed by a cellulase complex (NS50013) and β-glucosidase (NS50010) at 45°C. After saccharification, Saccharomyces cerevisiae was added for fermentation. The incubator was rotated at 120 rpm at 35°C. As a result of the pretreatment, the delignification efficiency was > 70% (170°C, 30 min) and temperature was found to be a significant factor in the removal of lignin than the reaction time. In addition, the saccharification results showed an enzymatic digestibility of > 90% when 40 FPU/g cellulose was used. The ethanol concentration reached 24.15 g/L in 24 h. This paper reports a total process for bioethanol production from agricultural biomass and an efficient pretreatment of lignocellulosic material.     

The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z

Background

Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping.

Results

Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus, three of the platypus sex chromosomes differ from those of the echidna and the order of several chromosomes is rearranged. Comparative gene mapping shows that, in addition to bird autosome regions, regions of bird Z chromosomes are homologous to regions in four platypus X chromosomes, that is, X₁, X₂, X₃, X₅, and in chromosome Y₁.

Conclusion

Monotreme sex chromosomes are easiest to explain on the hypothesis that autosomes were added sequentially to the translocation chain, with the final additions after platypus and echidna divergence. Genome sequencing and contig anchoring show no homology yet between platypus and therian Xs; thus, monotremes have a unique XY sex chromosome system that shares some homology with the avian Z.     

Genomic selection of purebreds for crossbred performance

Background

One of the main limitations of many livestock breeding programs is that selection is in pure breeds housed in high-health environments but the aim is to improve crossbred performance under field conditions. Genomic selection (GS) using high-density genotyping could be used to address this. However in crossbred populations, 1) effects of SNPs may be breed specific, and 2) linkage disequilibrium may not be restricted to markers that are tightly linked to the QTL. In this study we apply GS to select for commercial crossbred performance and compare a model with breed-specific effects of SNP alleles (BSAM) to a model where SNP effects are assumed the same across breeds (ASGM). The impact of breed relatedness (generations since separation), size of the population used for training, and marker density were evaluated. Trait phenotype was controlled by 30 QTL and had a heritability of 0.30 for crossbred individuals. A Bayesian method (Bayes-B) was used to estimate the SNP effects in the crossbred training population and the accuracy of resulting GS breeding values for commercial crossbred performance was validated in the purebred population.

Results

Results demonstrate that crossbred data can be used to evaluate purebreds for commercial crossbred performance. Accuracies based on crossbred data were generally not much lower than accuracies based on pure breed data and almost identical when the breeds crossed were closely related breeds. The accuracy of both models (ASGM and BSAM) increased with marker density and size of the training data. Accuracies of both models also tended to decrease with increasing distance between breeds. However the effect of marker density, training data size and distance between breeds differed between the two models. BSAM only performed better than AGSM when the number of markers was small (500), the number of records used for training was large (4000), and when breeds were distantly related or unrelated.

Conclusion

In conclusion, GS can be conducted in crossbred population and models that fit breed-specific effects of SNP alleles may not be necessary, especially with high marker density. This opens great opportunities for genetic improvement of purebreds for performance of their crossbred descendents in the field, without the need to track pedigrees through the system.     

Distribution of histopathology and Ia positive cells in actively induced and passively transferred experimental autoimmune orchitis

Histopathology in testes from mice with actively induced experimental orchitis (EAO) (active EAO) and those from recipients of testis-sensitized lymphocytes (passive EAO) had different distributions. In passive EAO, maximum orchitis existed in the straight tubules, rete testis, and ductus efferentes, obstruction of which led to extreme dilatation of seminiferous tubules. Unusual intralymphatic granulomata also resulted in dilated testicular lymphatics. In active EAO, maximum orchitis affected seminiferous tubules under the testicular capsule, away from the rete testes. Vasitis was common and occurred in both active and passive EAO. In normal testes, IA+ F4/80+ cells were sparse but formed a cuff around the straight tubules. After immunization with testis in adjuvant or with adjuvant alone, the number, size, and staining intensity of IA+ cells increased dramatically beginning on day 5, 7 days before disease onset. Simultaneously, epithelial cells confined to the ductus efferentes became Ia+. Although recipients of sensitized lymphocytes also developed epithelial Ia in the ductus efferentes, they did not show changes in testicular interstitial Ia+ cells. Our findings indicate that testicular autoantigens are not completely sequestered, but are accessible to and can react with passively transferred immune lymphocytes in well-defined regions of the germ cell compartment. These regions coincided to a large extent with maximum expression of periductal or epithelial Ia. Changes in Ia+ cells in the testis, which are inducible by adjuvants and precede orchitis, may account in part for the different distribution of histopathology of active EAO.     

Differential responsiveness to immunoablative therapy in refractory rheumatoid arthritis is associated with level and avidity of anti-cyclic citrullinated protein autoantibodies: a case study

In order to identify pathogenic correlates of refractory rheumatoid arthritis (RA), antibodies against anti-cyclic citrullinated protein (ACPAs) were investigated in RA patients in whom the dysregulated immune system had been ablated by high-dose chemotherapy (HDC) and autologous haematopoietic stem cell transplantation (HSCT). Six patients with refractory RA were extensively characterized in terms of levels of total immunoglobulins, RA-specific autoantibodies (ACPAs and rheumatoid factor) and antibodies against rubella, tetanus toxoid (TT) and phosphorylcholine before and after HDC plus HSCT. Additionally, the avidity of ACPAs was measured before and after treatment and compared with the avidity of TT antibodies following repeated immunizations. Synovial biopsies were obtained by arthroscopy before HDC plus HSCT, and analyzed by immunohistochemistry. In the three patients with clinically long-lasting responses to HDC plus HSCT (median 423 days), significant reductions in ACPA-IgG levels after therapy were observed (median level dropped from 215 to 34 arbitrary units/ml; P = 0.05). In contrast, stable ACPA-IgG levels were observed in three patients who relapsed shortly after HDC plus HSCT (median of 67 days). Clinical responders had ACPA-IgG of lower avidity (r = 0.75; P = 0.08) and higher degree of inflammation histologically (r = 0.73; P = 0.09). Relapse (after 38 to 530 days) in all patients was preceded by rising levels of low avidity ACPA-IgG (after 30 to 388 days), in contrast to the stable titres of high avidity TT antibodies. In conclusion, humoral autoimmune responses were differentially modulated by immunoablative therapy in patients with synovial inflammation and low avidity ACPA-IgG autoantibodies as compared with patients with high levels of high avidity ACPA-IgG. The distinct clinical disease course after immunoablative therapy based on levels and avidity of ACPA-IgG indicates that refractory RA is not a single disease entity.     

Enrichment of DNRA bacteria in a continuous culture

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are competing microbial nitrate-reduction processes. The occurrence of DNRA has been shown to be effected qualitatively by various parameters in the environment. A more quantitative understanding can be obtained using enrichment cultures in a laboratory reactor, yet no successful DNRA enrichment culture has been described. We showed that a stable DNRA-dominated enrichment culture can be obtained in a chemostat system. The enrichment was based on the hypothesis that nitrate limitation is the dominant factor in selecting for DNRA. First, a conventional denitrifying culture was enriched from activated sludge, with acetate and nitrate as substrates. Next, the acetate concentration in the medium was increased to obtain nitrate-limiting conditions. As a result, conversions shifted from denitrification to DNRA. In this selection of a DNRA culture, two important factors were the nitrate limitation and a relatively low dilution rate (0.026 h⁻¹). The culture was a highly enriched population of Deltaproteobacteria most closely related to Geobacter lovleyi, based on 16S rRNA gene sequencing (97% similarity). We established a stable and reproducible cultivation method for the enrichment of DNRA bacteria in a continuously operated reactor system. This enrichment method allows to further investigate the DNRA process and address the factors for competition between DNRA and denitrification, or other N-conversion pathways.