棉花“三桃”性状的QTL定位

棉花的"三桃"(伏前桃、伏桃和秋桃)一直以来被认为是棉花早熟高产的重要指标。文章以早熟高产棉百棉2号为核心亲本,分别与中晚熟材料TM-1和中棉所12杂交,获得两个组合的F2和F2:3家系群体。对两个组合进行了遗传连锁图谱构建,标记位点分别为269个和127个,图谱总长分别为1 837.8 cM和1 244.3 cM。两组合共检测到29个"三桃"性状QTL,包括16个可能性QTL和13个显著性QTL,其中,5个显著性QTL的LOD值既大于3又大于permutation阈值;16个QTL的贡献率大于10%,解释表型变异的10.9%～44.5%。在两组合的相同染色体共同标记附近检测到4个共同QTL,分别为伏前桃qPSB-17、伏桃qSB-17(qSB-17a/17b)和秋桃qAB-17、qAB-12/26,可用于棉花"三桃"性状的标记辅助选择;其中,伏桃qSB-17(qSB-17a/17b)在两个组合中的贡献率均大于10%,秋桃qAB-17、qAB-12/26在一个组合中的贡献率均大于10%,这些既共同又贡献率较大的QTL在标记辅助选择中应优先考虑。     

Activation of PI3K/AKT and MAPK pathway through a PDGFRβ-dependent feedback loop is involved in rapamycin resistance in hepatocellular carcinoma

Background

Rapamycin is an attractive approach for the treatment and prevention of HCC recurrence after liver transplantation. However, the objective response rates of rapamycin achieved with single-agent therapy were modest, supporting that rapamycin resistance is a frequently observed characteristic of many cancers. Some studies have been devoted to understanding the mechanisms of rapamycin resistance, however, the mechanisms are cell-type-dependent and studies on rapamycin resistance in HCC are extremely limited.

Methodology/Principal Findings

The anti-tumor sensitivity of rapamycin was modest in vitro and in vivo. In both human and rat HCC cells, rapamycin up-regulated the expression and phosphorylation of PDGFRβ in a time and dose-dependent manner as assessed by RT-PCR and western blot analysis. Using siRNA mediated knockdown of PDGFRβ, we confirmed that subsequent activation of AKT and ERK was PDGFRβ-dependent and compromised the anti-tumor activity of rapamycin. Then, blockade of this PDGFRβ-dependent feedback loop by sorafenib enhanced the anti-tumor sensitivity of rapamycin in vitro and in an immunocompetent orthotopic rat model of HCC.

Conclusions

Activation of PI3K/AKT and MAPK pathway through a PDGFRβ-dependent feedback loop compromises the anti-tumor activity of rapamycin in HCC, and blockade of this feedback loop by sorafenib is an attractive approach to improve the anti-tumor effect of rapamycin, particularly in preventing or treating HCC recurrence after liver transplantation.     

Mutant plant viruses with cell binding motifs provide differential adhesion strengths and morphologies

The ability of Tobacco mosaic virus (TMV) to tolerate various amino acid insertions near its carboxy terminus is well-known. Typically these inserts are based on antigenic sequences for vaccine development with plant viruses as carriers. However, we determined that the structural symmetries and the size range of the viruses could also be modeled to mimic the extracellular matrix proteins by inserting cell-binding sequences to the virus coat protein. The extracellular matrix proteins play important roles in guiding cell adhesion, migration, proliferation, and stem cell differentiation. Previous studies with TMV demonstrated that the native and phosphate-modified virus particles enhanced stem cell differentiation toward bone-like tissues. Based on these studies, we sought to design and screen multiple genetically modified TMV mutants with reported cell adhesion sequences to expand the virus-based tools for cell studies. Here, we report the design of these mutants with cell binding amino acid motifs derived from several proteins, the stabilities of the mutants against proteases during purification and storage, and a simple and rapid functional assay to quantitatively determine adhesion strengths by centrifugal adhesion assay. Among the mutants, we found that cells on TMV expressing RGD motifs formed filopodial extensions with weaker attachment profiles, whereas the cells on TMV expressing collagen I mimetic sequence displayed little spreading but higher attachment strengths.     

The passive yet successful way of planktonic life: genomic and experimental analysis of the ecology of a free-living polynucleobacter population

Background

The bacterial taxon Polynucleobacter necessarius subspecies asymbioticus represents a group of planktonic freshwater bacteria with cosmopolitan and ubiquitous distribution in standing freshwater habitats. These bacteria comprise <1% to 70% (on average about 20%) of total bacterioplankton cells in various freshwater habitats. The ubiquity of this taxon was recently explained by intra-taxon ecological diversification, i.e. specialization of lineages to specific environmental conditions; however, details on specific adaptations are not known. Here we investigated by means of genomic and experimental analyses the ecological adaptation of a persistent population dwelling in a small acidic pond.

Findings

The investigated population (F10 lineage) contributed on average 11% to total bacterioplankton in the pond during the vegetation periods (ice-free period, usually May to November). Only a low degree of genetic diversification of the population could be revealed. These bacteria are characterized by a small genome size (2.1 Mb), a relatively small number of genes involved in transduction of environmental signals, and the lack of motility and quorum sensing. Experiments indicated that these bacteria live as chemoorganotrophs by mainly utilizing low-molecular-weight substrates derived from photooxidation of humic substances.

Conclusions

Evolutionary genome streamlining resulted in a highly passive lifestyle so far only known among free-living bacteria from pelagic marine taxa dwelling in environmentally stable nutrient-poor off-shore systems. Surprisingly, such a lifestyle is also successful in a highly dynamic and nutrient-richer environment such as the water column of the investigated pond, which was undergoing complete mixis and pronounced stratification in diurnal cycles. Obviously, metabolic and ecological versatility is not a prerequisite for long-lasting establishment of abundant bacterial populations under highly dynamic environmental conditions. Caution should be exercised when generalizing the obtained insights into the ecology and adaptation of the investigated lineage to other Polynucleobacter lineages.     

Epidemiological, virological, and entomological characteristics of dengue from 1978 to 2009 in Guangzhou, China

To understand its unprecedented resurgence, we examined the epidemiological, virological, and entomological features of dengue in Guangzhou during 1978-2009. Cases reported to the Guangzhou Centre for Disease Control and Prevention and data from virological and entomological surveillance were analyzed from three periods: 1978-1988, 1989-1999, and 2000-2009. Although cases decreased over time: 6,649 (1978-1988) to 6,479 (1989-1999) to 2,526 (2000-2009), geographical expansion resulted in districts with an average incidence >2.5/100,000, increasing from five (1978-1988, 1989-1999) to seven (2000-2009). Age distribution (mean age: 34.9 years) provided a trend of increasing dengue incidence among adults, and there was a significantly higher incidence among men with a sex ratio of 1.15:1 (P<0.001). Cases occurred from May through November with a peak between August and October, and a long-term trend was characterized by a three to five-year cyclical pattern. The most frequently isolated serotypes were DENV-2 (1978-1988) and DENV-1 (1989-1999 and 2000-2009). Seasonal fluctuations in immature densities of Aedes albopictus (sole transmission vector in Guangzhou) were consistent with the dengue seasonality. After a 30-year apparent absence, DENV-3 had reemerged in 2009. The current epidemiological situation is highly conducive to periodic dengue resurgences. Thus, a high degree of surveillance and strict control measures in source reduction should be maintained.     

Seed regeneration potential of canopy gaps at early formation stage in temperate secondary forests, Northeast China

Promoting the seed regeneration potential of secondary forests undergoing gap disturbances is an important approach for achieving forest restoration and sustainable management. Seedling recruitment from seed banks strongly determines the seed regeneration potential, but the process is poorly understood in the gaps of secondary forests. The objectives of the present study were to evaluate the effects of gap size, seed availability, and environmental conditions on the seed regeneration potential in temperate secondary forests. It was found that gap formation could favor the invasion of more varieties of species in seed banks, but it also could speed up the turnover rate of seed banks leading to lower seed densities. Seeds of the dominant species, Fraxinus rhynchophylla, were transient in soil and there was a minor and discontinuous contribution of the seed bank to its seedling emergence. For Quercus mongolica, emerging seedling number was positively correlated with seed density in gaps (R?=?0.32, P<0.01), especially in medium and small gaps (<500 m(2)). Furthermore, under canopies, there was a positive correlation between seedling number and seed density of Acer mono (R?=?0.43, P<0.01). Gap formation could promote seedling emergence of two gap-dependent species (i.e., Q. mongolica and A. mono), but the contribution of seed banks to seedlings was below 10% after gap creation. Soil moisture and temperature were the restrictive factors controlling the seedling emergence from seeds in gaps and under canopies, respectively. Thus, the regeneration potential from seed banks is limited after gap formation.     

Cell origins and diagnostic accuracy of interleukin 27 in pleural effusions

The objective of the present study was to investigate the presence of interleukin (IL)-27 in pleural effusions and to evaluate the diagnostic significance of pleural IL-27. The concentrations of IL-27 were determined in pleural fluids and sera from 68 patients with tuberculous pleural effusion, 63 malignant pleural effusion, 22 infectious pleural effusion, and 21 transudative pleural effusion. Flow cytometry was used to identify which pleural cell types expressed IL-27. It was found that the concentrations of pleural IL-27 in tuberculous group were significantly higher than those in malignant, infectious, and transudative groups, respectively. Pleural CD4(+) T cells, CD8(+) T cells, NK cells, NKT cells, B cells, monocytes, macrophages, and mesothelial cells might be the cell sources for IL-27. IL-27 levels could be used for diagnostic purpose for tuberculous pleural effusion, with the cut off value of 1,007 ng/L, IL-27 had a sensitivity of 92.7% and specificity of 99.1% for differential diagnosing tuberculous pleural effusion from non-tuberculous pleural effusions. Therefore, compared to non-tuberculous pleural effusions, IL-27 appeared to be increased in tuberculous pleural effusion. IL-27 in pleural fluid is a sensitive and specific biomarker for the differential diagnosing tuberculous pleural effusion from pleural effusions with the other causes.     

A new pentapeptide compound, PLNPK, ameliorates anti-glomerular basement membrane nephritis in Wistar rats

PLNPK is a pentapeptide compound extracted from pig spleen with a Pro-Leu-Asn-Pro-Lys molecular structure. The spleen is the biggest immune organ in the body, in which there are lots of immunocytes and immune molecules. Our pilot study showed that PLNPK could suppress the transformation and proliferation of T lymphocytes and the production of antibodies in mice. It is widely accepted that most types of glomerulonephritis are immunological diseases caused by the reaction of antigen and antibody. Both humoral immunity and cell-mediated immunity contribute to the progress of these diseases, and suppression of immunoreactions and inflammation is important to ameliorate nephritis. After the immunosuppressive effects of this compound were discovered, this study also examined whether PLNPK had beneficial effects on a rat model of glomerulonephritis. The results suggested PLNPK (200microg/kg/d and 400microg/kg/d) reduced urinary protein excretion, lessened the deposit of autoantibodies along the glomerular basement membrane (GBM), reduced formation of crescent and protein casts, and ameliorated glomerular fibrosis and GBM injury. After treatment with PLNPK (200microg/kg/d and 400microg/kg/d) for 7 days, macrophage infiltration in the glomeruli was markedly reduced. Our results suggest that PLNPK has a beneficial effect on rat anti-GBM nephritis.     

Complete genome sequence of seawater bacterium Glaciecola nitratireducens FR1064(T)

Glaciecola nitratireducens strain FR1064(T) was isolated from seawater and described as a new species by Baik et al. in 2006. The genome size is about 1.01 to 1.26 Mb smaller than two reported Glaciecola genomes, indicating the gain or loss of large genome segments in the evolution of Glaciecola strains.