裸子植物psbA基因分子进化式样的研究

为阐明裸子植物对陆生生境生态响应的分子机制,以新近的裸子植物分类系统为指导,基于psb A基因编码全序列对4亚纲53种代表植物进行分子进化分析。首先,依据"放松分子钟"模型重建裸子植物在时间尺度下系统发育关系;其次,采用6个模型(MEC/JTT、MEC/cp REV、M5、M7、M8、M8a)估测氨基酸位点ω值,并对各模型结果进行统计检测;随后,利用Bootstrap方法检PSBA蛋白内部氨基酸位点的共进化动态。结果表明,系统树提示的物种分化历程支持前期分类结果;光合系统反应中心核心PSBA蛋白有3个氨基酸位点(13、19和243)曾经受正选择压力;PSBA蛋白内部有多对氨基酸位点间构成了共进化网络。因此,psb A基因编码序列具有作为描绘裸子植物系统发育关系标记的潜力,PSBA蛋白部分位点经历了适应性进化,通过位点间共进化网络协同作用方式辅助裸子植物响应陆生生境。     

紫花苜蓿赤霉素受体基因的克隆及表达分析

赤霉素受体(GID)是赤霉素信号转导途径的重要成员,直接影响着赤霉素对植物体效应的发挥。该研究利用同源克隆的方法,首次从紫花苜蓿中克隆得到1个赤霉素受体基因,命名为MsGID1b。序列分析发现,MsGID1b基因开放阅读框长度为1 053bp,编码350个氨基酸,推测其蛋白质分子量为39.839kD,是一个无信号肽和跨膜结构的亲水性蛋白。序列比对结果表明,MsGID1b基因与蒺藜苜蓿MtGID1b基因的核苷酸序列相似性为98%,氨基酸序列相似性为99%,且具有HSL家族典型的HGG和GXSXG保守结构域及GA、DELLA蛋白结合位点。荧光定量PCR分析表明,MsGID1b基因在紫花苜蓿各组织中的表达丰度依次为:根盛花初花茎叶荚果;经GA3、ABA、NaCl、PEG和黑暗诱导后该基因表达上调,尤其是在GA3诱导下,MsGID1b基因的表达量一直维持在较高水平,表明MsGID1b基因可能参与紫花苜蓿的抗逆调控。     

Genome sequence of <Emphasis Type="Italic">Candida versatilis</Emphasis> and comparative analysis with other yeast

The genome of Candida versatilis was sequenced to understand its characteristics in soy sauce fermentation. The genome size of C. versatilis was 9.7 Mb, the content of G + C was 39.74 %, scaffolds of N50 were 1,229,640 bp in length, containing 4711 gene. There were predicted 269 tRNA genes and 2201 proteins with clear function. Moreover, the genome information of C. versatilis was compared with another salt-tolerant yeast Zygosaccharomyces rouxii and the model organism Saccharomyces cerevisiae. C. versatilis and Z. rouxii genome size was close and both smaller than 12.1 for the Mb of S. cerevisiae. Using the OrthoMCL protein, three genomes were divided into 4663 groups. There were about 3326 homologous proteins in C. versatilis, Z. rouxii and S. cerevisiae.     

Genetic analysis and characterization of a new maize association mapping panel for quantitative trait loci dissection

Association mapping based on the linkage disequilibrium provides a promising tool to identify genes responsible for quantitative variations underlying complex traits. Presented here is a maize association mapping panel consisting of 155 inbred lines with mainly temperate germplasm, which was phenotyped for 34 traits and genotyped using 82 SSRs and 1,536 SNPs. Abundant phenotypic and genetic diversities were observed within the panel based on the phenotypic and genotypic analysis. A model-based analysis using 82 SSRs assigned all inbred lines to two groups with eight subgroups. The relative kinship matrix was calculated using 884 SNPs with minor allele frequency ≥20% indicating that no or weak relationships were identified for most individual pairs. Three traits (total tocopherol content in maize kernel, plant height and kernel length) and 1,414 SNPs with missing data <20% were used to evaluate the performance of four models for association mapping analysis. For all traits, the model controlling relative kinship (K) performed better than the model controlling population structure (Q), and similarly to the model controlling both population structure and relative kinship (Q + K) in this panel. Our results suggest this maize panel can be used for association mapping analysis targeting multiple agronomic and quality traits with optimal association model.     

Structure and mechanism of Escherichia coli glutathionylspermidine amidase belonging to the family of cysteine; histidine-dependent amidohydrolases/peptidases

The bifunctional Escherichia coli glutathionylspermidine synthetase/amidase (GspSA) catalyzes both the synthesis and hydrolysis of Gsp. Its amidase domain (GspA), which catalyzes the hydrolysis of Gsp into glutathione and spermidine, plays an important role in redox sensing and protein S-thiolation. To gain insight of the regulation and catalytic mechanism of and further understand the recycling of the Gsp dimer and Gsp-S-protein adducts, we solved two crystal structures of GspA and GspSA both with the C59A mutation and bound with the substrate, Gsp. In both structures, Cys59, His131, and Glu147 form the catalytic triad, which is similar to other cysteine proteases. Comparison of the GspA_Gsp complex and apo GspSA structures indicates that on binding with Gsp, the side chains of Asn149 and Gln58 of the amidase domain are induced to move closer to the carbonyl oxygen of the cleaved amide bond of Gsp, thereby participating in catalysis. In addition, the helix-loop region of GspA, corresponding to the sequence (30)YSSLDPQEYEDDA(42), involves in regulating the substrate binding. Our previous study indicated that the thiol of Cys59 of GspA is only oxidized to sulfenic acid by H(2)O(2). When comparing the active site of GspA with those of other cysteine proteases, we found that limited space and hydrophobicity of the environment around Cys59 play an important role to inhibit its further oxidation. The structural results presented here not only elucidate the catalytic mechanism and regulation of GspA but also help us to design small molecules to inhibit or probe for the activity of GspA.     

Elevated BCRP/ABCG2 expression confers acquired resistance to gefitinib in wild-type EGFR-expressing cells

Background

The sensitivity of non-small cell lung cancer (NSCLC) patients to EGFR tyrosine kinase inhibitors (TKIs) is strongly associated with activating EGFR mutations. Although not as sensitive as patients harboring these mutations, some patients with wild-type EGFR (wtEGFR) remain responsive to EGFR TKIs, suggesting that the existence of unexplored mechanisms renders most of wtEGFR-expressing cancer cells insensitive.

Methodology/Principal Findings

Here, we show that acquired resistance of wtEGFR-expressing cancer cells to an EGFR TKI, gefitinib, is associated with elevated expression of breast cancer resistance protein (BCRP/ABCG2), which in turn leads to gefitinib efflux from cells. In addition, BCRP/ABCG2 expression correlates with poor response to gefitinib in both cancer cell lines and lung cancer patients with wtEGFR. Co-treatment with BCRP/ABCG2 inhibitors enhanced the anti-tumor activity of gefitinib.

Conclusions/Significance

Thus, BCRP/ABCG2 expression may be a predictor for poor efficacy of gefitinib treatment, and targeting BCRP/ABCG2 may broaden the use of gefitinib in patients with wtEGFR.     

Complete genome sequence and updated annotation of Desulfovibrio alaskensis G20

Desulfovibrio alaskensis G20 (formerly Desulfovibrio desulfuricans G20) is a Gram-negative mesophilic sulfate-reducing bacterium (SRB), known to corrode ferrous metals and to reduce toxic radionuclides and metals such as uranium and chromium to sparingly soluble and less toxic forms. We present the 3.7-Mb genome sequence to provide insights into its physiology.     

Comparison of HIV-, HBV-, HCV- and co-infection prevalence between Chinese and Burmese intravenous drug users of the China-Myanmar border region

Background

Co-infection with HIV and HCV and/or HBV is highly prevalent in intravenous drug users (IDUs). Because of the proximity to the “Golden Triangle”, HIV prevalence among the IDUs is very high in the China-Myanmar border region. However, there are few studies about co-infection with HIV and HCV and/or HBV, especially in the region that belongs to Myanmar.

Methods

721 IDUs, including 403 Chinese and 318 Burmese, were investigated for their HIV, hepatitis B virus (HBV), and hepatitis C virus (HCV) serological status. Statistical analysis was performed to evaluate the differences of the epidemic situation between the Chinese IDUs and the Burmese IDUs.

Results

Among the Chinese IDUs and the Burmese IDUs, HCV infection was the most prevalent (69.0% vs 48.1%, P<0.001), followed by HBV (51.6% vs 43.1%, P<0.05) and HIV (33.7% vs 27.0%, P>0.05). Besides, there were more HIV-HBV co-infected IDUs (20.1% vs 11.3%, P<0.005), and HIV-HCV co-infected IDUs (31.8% vs 23.9%, P<0.05) in China than in Myanmar, as well as HIV-HBV-HCV triple infection (19.1% vs 10.4%, P<0.005).

Conclusion

Co-infection with HIV and HCV and/or HBV is highly prevalent among the IDUs in the China-Myanmar border region. The HIV epidemic appears to be in a downward trend, compared with previous reports. However, all infections were more prevalent among the Chinese IDUs than among the Burmese.     

Quantification of CPT13 in rat plasma using LC-MS/MS for a pharmacokinetic study

A new, simple, sensitive and specific reversed-phase high performance liquid chromatographic (HPLC) method using tandem mass spectrometry detection was initially developed and validated for the analysis of 10-(2-pyrazolyl-ethoxy)-(20S)-camptothecin (CPT13) in rat plasma. Pretreatment of the sample obtained from plasma involved a single protein precipitation step with using acetonitrile containing 0.1% formic acid. An aliquot of 20 μl was injected into a C-18 column. The chromatographic separation was achieved using the mobile phase consisting of acetonitrile:water (35:65) at a flow rate of 1.0 mL/min. The total run time for each sample was 10 min, and camptothecin (CPT, IS) and CPT13 were well separated with retention times of 5.1 min and 5.6 min, respectively. Detection was performed using a triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode via an electrospray ionization (ESI) source. The calibration curve was linear (r2 = 0.9998) over the concentration range of 1-1000 ng/mL, with a LLOQ of 1 ng/mL for CPT13. The inter- and intra-day precision (%R.S.D.) were <2.58% and 6.28%, respectively, and the accuracies (%) were within the range of 97.34-110.67%. CPT13 in rat plasma was stable when stored at -20 °C or 4 °C for three freeze-thaw cycles, The method was employed for the first time during pharmacokinetic studies of CPT13 in rats following a single intravenous dose (0.1 mg/kg) and three different oral doses (50 mg/kg, 30 mg/kg, and 10 mg/kg). This fully validated method was successfully applied to a pharmacokinetic study of CPT13 in rats.     

White shrimp Litopenaeus vannamei immersed in seawater containing Sargassum hemiphyllum var. chinense powder and its extract showed increased immunity and resistance against Vibrio alginolyticus and white spot syndrome virus

This study was to examine the immune response of white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus and WSSV when shrimp received the Sargassum hemiphyllum var. chinense powder and its hot-water extract. Both powder and extract showed activation of prophenoloxidase and generation of superoxide anion in the shrimp in vitro. The haemocyte count, phenoloxidase (PO) activity, respiratory burst, and lysozyme activity were examined after the shrimp were immersed in seawater containing S. hemiphyllum var. chinense powder or its extract at 0, 100, 300, and 500 mg L?1 for 1, 3, and 5 h. These immune parameters of shrimp immersed in 300 and 500 mg L?1 powder, and 100 and 300 mg L?1 extract were significantly higher than those of control shrimp after 3 h, but slightly decreased after 5 h. In another experiment, shrimp immersed in seawater containing the powder or the extract at 0, 100, 300, and 500 mg L?1 after 3 h were challenged with V. alginolyticus at 8 × 10? colony-forming unit (cfu) shrimp?1, or challenged with WSSV at 1 × 10? copies shrimp?1, and then placed in seawater. Survival rate of shrimp immersed in 500 mg L?1 powder was significantly higher than that of control shrimp after 24-120 h in the V. alginolyticus-challenge test, and after 72 h in the WSSV-challenge test, respectively. Survival rate of shrimp immersed in 300 mg L?1 extract was significantly higher than that of control shrimp after 72-120 h in both V. alginolyticus-challenge and WSSV-challenge tests. It was concluded that the shrimp immersed in seawater containing the powder at 500 mg L?1, and the extract at 300 mg L?1 had increased immunity and resistance against V. alginolyticus infection, and the shrimp that received extract at 300 mg L?1 showed resistance against WSSV infection.