毛白杨幼苗叶片生长及其光合参数和硼转运蛋白基因对高硼胁迫的响应

该研究采用毛白杨(Populus tomentosa)为试验材料,分析了温室条件下沙培幼苗对短期高硼胁迫(1、5、10 mmol/L硼酸)下的叶片生长、光合参数和硼转运蛋白的响应特征。结果显示:(1)与对照(0.05 mmol/L硼酸)相比,1 mmol/L硼酸处理导致毛白杨幼苗叶片叶绿素荧光参数上调,活性氧含量上升,树苗基部叶片出现少量黑色坏死斑;5 mmol/L硼酸胁迫下,叶片净光合速率、气孔导度和蒸腾速率下调,胞间二氧化碳浓度上升,叶绿素荧光参数和过氧化氢含量进一步上调,超氧阴离子含量较1 mmol/L硼酸胁迫时下调但仍然高于对照,除顶部叶片之外的其他叶片上出现大量坏死斑;10 mmol/L硼酸胁迫下,气体交换参数、叶绿素荧光参数和活性氧含量与5 mmol/L硼酸胁迫时相似,所有叶片均在平行于次级叶脉的方向出现呈带状分布的坏死斑。(2)毛白杨幼苗根和茎硼含量在硼胁迫条件下与对照相比变化幅度较小,而叶片硼含量在5 mmol/L和10 mmol/L硼酸胁迫下比对照显著上升,此时硼转移系数和生物富集系数均维持较高的水平。(3)硼转运蛋白(BOR)基因家族成员中PtoBOR4和PtoBOR8在根中的表达水平随着外界硼浓度的增加呈先上升后下降的趋势;在茎中,PtoBOR3基因下调表达,PtoBOR5上调表达;在叶片中,PtoBOR4表达先上升后下降,而PtoBOR7和PtoBOR8上调表达。研究表明,毛白杨幼苗叶片叶绿素荧光参数、活性氧、气体交换参数及硼转运蛋白基因家族表达对高硼胁迫较为敏感,硼胁迫症状在较短的时间内在叶片上以坏死斑的形式出现,可能与其较强的控制根系硼浓度的能力和向地上部分迅速运输硼的能力有关。     

Angle-Insensitive Color Filters Based on Multilayer Ultrathin-Film Structures

Plasmonics - Color filters utilize optical resonance in thin-film nanostructures to obtain vivid reflective or transmissive colors, which has attracted a lot of attention recently. Here, we report...     

Genetic Variants from Lipid-Related Pathways and Risk for Incident Myocardial Infarction

Background

Circulating lipids levels, as well as several familial lipid metabolism disorders, are strongly associated with initiation and progression of atherosclerosis and incidence of myocardial infarction (MI).

Objectives

We hypothesized that genetic variants associated with circulating lipid levels would also be associated with MI incidence, and have tested this in three independent samples.

Setting and Subjects

Using age- and sex-adjusted additive genetic models, we analyzed 554 single nucleotide polymorphisms (SNPs) in 41 candidate gene regions proposed to be involved in lipid-related pathways potentially predisposing to incidence of MI in 2,602 participants of the Swedish Twin Register (STR; 57% women). All associations with nominal P<0.01 were further investigated in the Uppsala Longitudinal Study of Adult Men (ULSAM; N = 1,142).

Results

In the present study, we report associations of lipid-related SNPs with incident MI in two community-based longitudinal studies with in silico replication in a meta-analysis of genome-wide association studies. Overall, there were 9 SNPs in STR with nominal P-value <0.01 that were successfully genotyped in ULSAM. rs4149313 located in ABCA1 was associated with MI incidence in both longitudinal study samples with nominal significance (hazard ratio, 1.36 and 1.40; P-value, 0.004 and 0.015 in STR and ULSAM, respectively). In silico replication supported the association of rs4149313 with coronary artery disease in an independent meta-analysis including 173,975 individuals of European descent from the CARDIoGRAMplusC4D consortium (odds ratio, 1.03; P-value, 0.048).

Conclusions

rs4149313 is one of the few amino acid changing variants in ABCA1 known to associate with reduced cholesterol efflux. Our results are suggestive of a weak association between this variant and the development of atherosclerosis and MI.     

Transforming Growth Factor β Inhibits Platelet Derived Growth Factor-Induced Vascular Smooth Muscle Cell Proliferation via Akt-Independent,Smad-Mediated Cyclin D1 Downregulation

In adult tissue, vascular smooth muscle cells (VSMCs) exist in a differentiated phenotype, which is defined by the expression of contractile proteins and lack of proliferation. After vascular injury, VSMC adopt a synthetic phenotype associated with proliferation, migration and matrix secretion. The transition between phenotypes is a consequence of the extracellular environment, and in particular, is regulated by agonists such as the pro-differentiating cytokine transforming growth factor β (TGFβ) and the pro-proliferative cytokine platelet derived growth factor (PDGF). In this study, we investigated the interplay between TGFβ and PDGF with respect to their ability to regulate VSMC proliferation. Stimulation of human aortic VSMC with TGFβ completely blocked proliferation induced by all isoforms of PDGF, as measured by DNA synthesis and total cell number. Mechanistically, PDGF-induced Cyclin D1 mRNA and protein expression was inhibited by TGFβ. TGFβ had no effect on PDGF activation of its receptor and ERK1/2, but inhibited Akt activation. However, constitutively active Akt did not reverse the inhibitory effect of TGFβ on Cyclin D1 expression even though inhibition of the proteasome blocked the effect of TGFβ. siRNA against Smad4 completely reversed the inhibitory effect of TGFβ on PDGF-induced Cyclin D1 expression and restored proliferation in response to PDGF. Moreover, siRNA against KLF5 prevented Cyclin D1 upregulation by PDGF and overexpression of KLF5 partially reversed TGFβ-induced inhibition of Cyclin D1 expression. Taken together, our results demonstrate that KLF5 is required for PDGF-induced Cyclin D1 expression, which is inhibited by TGFβ via a Smad dependent mechanism, resulting in arrest of VSMCs in the G1 phase of the cell cycle.     

Comparisons of cadmium tolerance and accumulation at seedling stage in wheat varieties grown in different decades in China

Cadmium (Cd) tolerance and accumulation in wheat varieties were investigated at seedling stage under a controlled environmental condition. The 46 leading wheat varieties cultivated from the 1950s to 2000s in China were treated at the three-leaf stage with a 50 μM CdCl₂ solution for 24 days. Growth and photosynthesis parameters were measured and the Cd-tolerance index (ratio of a given parameter under Cd treatment to that of the control) was determined. Cd accumulation in shoots and roots and Cd translocation were also determined. It was found that Cd tolerance and accumulation of these wheat varieties varied over the different decades. Principal components analysis (PCA) showed that wheat varieties in 1950s and 1980s were tolerant while varieties from the last decade were sensitive to Cd stress. Wheat varieties in 1960s and 1970s were particularly tolerant to Cd stress for the parameters of shoot height, secondary root numbers, net photosynthesis and transpiration rate while the varieties in the 1990s were sensitive to Cd stress for shoot dry weight and root dry weight. Comparing each decade to the average Cd translocation ratio from the roots to the shoots for the whole period, the varieties from the 1950s and 1960s had a higher translocation ratio, while varieties in the 1970s were below that average. Varieties from the 1980s to 2000s showed an average translocation ratio. Using cluster analysis (CA), Shannongfu 63, Yangmai 1 and Yangmai 158 were the most Cd-tolerant varieties in which Cd translocation ratio were low, and Yumai 18 and Huaimai 20 were the most Cd-sensitive varieties in which Cd translocation ratio were high. The results indicating that wheat varieties from different decades were different in Cd tolerance and accumulation, and could be useful for breeding wheat for Cd stress tolerance.     

氦氧饱和高气压暴露对铜绿假单胞菌PAO1基因表达的诱导调节

研究氦氧饱和高气压暴露对铜绿假单胞菌基因表达谱的系统影响,对急性毒力基因表达的调节。用全基因组DNA芯片分析技术比较菌株暴露前后基因表达谱差异;RT-PCR方法验证部分差异表达基因;用分光光度法在细胞水平验证弹性蛋白酶含量;小鼠染毒法观察暴露组细菌毒力在整体动物水平的变化。基因表达谱分析结果表明,铜绿假单胞菌暴露12 h差异表达基因达243个、72 h差异表达基因为1 168个。72 h差异表达基因中与细菌应激响应、蛋白折叠、转录调节、菌毛和鞭毛合成、毒力因子调节与合成、细菌外膜蛋白和抗原合成的基因大量上调;部分基因的RT-PCR验证结果与芯片结果一致;细胞水平验证结果显示暴露72 h细菌毒力表型增强。因此,氦氧饱和高气压暴露对铜绿假单胞菌基因表达谱有明显影响,对急性侵袭性感染毒力因子基因表达水平有正向诱导调节作用。     

Changes in follicular blood flow and nitric oxide levels in follicular fluid during follicular deviation in cows

Two experiments were conducted to test the hypothesis that there are dynamic changes in follicular blood flow during follicular deviation and that nitric oxide (NO) in follicular fluid (FF) plays a role in regulation of follicular blood flow. In Experiment I, follicular blood flow of the two largest follicles was monitored by using Power Doppler ultrasonography during follicular deviation in sixteen follicular waves during eight estrous cycles in eight cows. Blood flow did not differ (P>0.05) between the dominant follicle (DF) and the largest subordinate follicle (SF) until the beginning of the deviation of the follicular size, but was higher (P<0.05) in DF than in the largest SF one and two days after the beginning of diameter deviation in ovulatory (n=5) and atretic (n=11) waves; respectively. In Experiment II, FF was aspirated from DF and the largest SF on the day of diameter deviation (DF, n=6; SF, n=6) and two days later (DF, n=12; SF, n=9). Nitric oxide did not differ (P>0.05) between DF and the largest SF on the day of diameter deviation but, one or two days after observed diameter deviation NO concentrations were lower (P<0.01) in DF compared to the largest SF. On the day of diameter deviation and two days later E2 levels in FF were higher (P<0.01) in DF than in the largest SF. P4 concentrations in FF were higher (P<0.05) in DF than in the largest SF on the day of diameter deviation, but did not (P>0.05) differ two days later. E2/P4 ratio in FF was the same (P>0.05) in DF and the largest SF on the day of diameter deviation, but was higher (P<0.01) in DF than in the largest SF one or two days later. In conclusion, area of follicular blood flow of DF and the largest SF increased in parallel with follicular size during follicular deviation. Furthermore, there were relationships between changes in follicular blood flow, NO concentrations and E2/P4 ratio in FF following the beginning of diameter deviation in cattle.     

Toxoplasma gondii RH Ankara: production of evolving tachyzoites using a novel cell culture method

Nitric oxide (NO) and NO-derived reactive nitrogen species (RNS) are present in the food vacuole (FV) of Plasmodium falciparum trophozoites. The product of PFL1555w, a putative cytochrome b₅, localizes in the FV membrane, similar to what was previously observed for the product of PF13_0353, a putative cytochrome b₅ reductase. These two gene products may contribute to NO generation by denitrification chemistry from nitrate and/or nitrite present in the erythrocyte cytosol. The possible coordination of NO to heme species present in the food vacuole was probed by resonance Raman spectroscopy. The spectroscopic data revealed that in situ generated NO interacts with heme inside the intact FVs to form ferrous heme nitrosyl complexes that influence intra-vacuolar heme solubility. The formation of heme nitrosyl complexes within the FV is a previously unrecognized factor that could affect the equilibrium between soluble and crystallized heme within the FV in vivo.