Effects of lead and cadmium on photosynthesis in Amaranthus spinosus and assessment of phytoremediation potential

Abstract

This study assessed the effects of Pb (0, 200, 500, 1000?mg kg^?1) and Cd (0, 5, 15, 30, 50?mg kg^?1) on photosynthesis in Amaranthus spinosus (A. spinosus), as well as the potential for phytoremediation by pot-culture experiment. Exposure to Pb/Cd produced a concentration-dependent decrease in biomass and all photosynthesis parameters, except for non-photochemical quenching, which increased with the metal concentration. The metals accumulated more in roots compared to shoots. The bioconcentration factor (BCF) of Pb was <1 in shoots at all Pb levels, whereas the BCF was <1 in roots at all but the lowest concentration of Pb. Roots extracted Cd from soil at all treatments. The translocation factor of Cd was larger than that of Pb suggesting that Cd is more mobile than Pb in A. spinosus. Amaranthus spinosus displays a high tolerance for both Pb and Cd with regards to growth and photochemical efficiency, but it is more sensitive to Cd than Pb. Amaranthus spinosus accumulates Pb and Cd primarily in the roots and Cd is more bioconcentrated and translocated in comparison to Pb. This investigation shows that A. spinosus has good potential for phytoremediation of soils contaminated by low levels of Cd and Pb.     

Three enigmatic BioH isoenzymes are programmed in the early stage of mycobacterial biotin synthesis,an attractive anti-TB drug target

Tuberculosis (TB) is one of the leading infectious diseases of global concern, and one quarter of the world’s population are TB carriers. Biotin metabolism appears to be an attractive anti-TB drug target. However, the first-stage of mycobacterial biotin synthesis is fragmentarily understood. Here we report that three evolutionarily-distinct BioH isoenzymes (BioH1 to BioH3) are programmed in biotin synthesis of Mycobacterium smegmatis. Expression of an individual bioH isoform is sufficient to allow the growth of an Escherichia coli ΔbioH mutant on the non-permissive condition lacking biotin. The enzymatic activity in vitro combined with biotin bioassay in vivo reveals that BioH2 and BioH3 are capable of removing methyl moiety from pimeloyl-ACP methyl ester to give pimeloyl-ACP, a cognate precursor for biotin synthesis. In particular, we determine the crystal structure of dimeric BioH3 at 2.27Å, featuring a unique lid domain. Apart from its catalytic triad, we also dissect the substrate recognition of BioH3 by pimeloyl-ACP methyl ester. The removal of triple bioH isoforms (ΔbioH1/2/3) renders M. smegmatis biotin auxotrophic. Along with the newly-identified Tam/BioC, the discovery of three unusual BioH isoforms defines an atypical ‘BioC-BioH(3)’ paradigm for the first-stage of mycobacterial biotin synthesis. This study solves a long-standing puzzle in mycobacterial nutritional immunity, providing an alternative anti-TB drug target.     

紫杉醇生物合成的研究进展

本文对近年来研究紫杉醇的生物合成及生物合成途径中关键酶的进展进行了评述。目前紫杉醇的生物合成途径已经基本明了,其生物合成途径中环化酶的基因已经克隆成功。在分子及基因水平上大量生产紫杉醇的曙光已经出现。     

酵母菌中表达的新疆家蚕抗菌肽（Cecropin-XJ）的特性研究

研究酵母菌中表达的新疆家蚕抗菌肽 (CecropinXJ)的抗菌特性。根据琼脂孔穴扩散法,检测抗菌肽的热稳定性、抑菌效价、对氨苄青霉素抗性菌的抑菌作用,并检测了抗菌肽对酸碱盐、人造胃液的耐受性及其抗菌谱。结果显示新疆家蚕抗菌肽具有很强的热稳定性、能够杀灭氨苄青霉素抗性菌、对酸碱盐、人造胃酸有一定的耐受性,其杀菌活力为：1mg抗菌肽与1200U的氨苄青霉素杀菌活力相当。新疆家蚕抗菌肽能够不同程度地杀灭革兰氏阳性菌和革兰氏阴性菌,这一发现将为抗菌肽在农业、医疗卫生、畜牧业等方面的应用奠定基础,同时为深入研究抗菌肽作用机制提供了依据。     

The plastid-encoded protein Orf2971 is required for protein translocation and chloroplast quality control

Photosynthesis and the biosynthesis of many important metabolites occur in chloroplasts. In these semi-autonomous organelles, the chloroplast genome encodes approximately 100 proteins. The remaining chloroplast proteins, close to 3,000, are encoded by nuclear genes whose products are translated in the cytosol and imported into chloroplasts. However, there is still no consensus on the composition of the protein import machinery including its motor proteins and on how newly imported chloroplast proteins are refolded. In this study, we have examined the function of orf2971, the largest chloroplast gene of Chlamydomonas reinhardtii. The depletion of Orf2971 causes the accumulation of protein precursors, partial proteolysis and aggregation of proteins, increased expression of chaperones and proteases, and autophagy. Orf2971 interacts with the TIC (translocon at the inner chloroplast envelope) complex, catalyzes ATP (adenosine triphosphate) hydrolysis, and associates with chaperones and chaperonins. We propose that Orf2971 is intimately connected to the protein import machinery and plays an important role in chloroplast protein quality control.

Repression of Orf2971 induces accumulation of chloroplast precursor proteins and impaired chloroplast quality indicating that Orf2971 is required for protein import and chloroplast quality control.

IN A NUTSHELL Background: The chloroplast is an important bioreactor as well as a photosynthetic site. Approximately 3,000 plastid proteins encoded in the nucleus are translocated into the chloroplast envelope via the TOC (translocon at the outer chloroplast envelope) and TIC machineries. Most nucleus-encoded preproteins that enter the plastid are unfolded as they traverse the TOC–TIC import complexes. To prevent these unfolded or misfolded proteins from causing chloroplast damage, a quality control mechanism comprising molecular chaperones and proteases ensures that all polypeptides entering chloroplasts are either correctly folded or degraded. However, there is still no consensus on the TIC complex’s components, motor proteins, or mechanism for refolding proteins entering the chloroplast. Question: What is the precise function of each of the proteins in the TIC complex? What is the composition of the chloroplast protein import machinery motor? How are the newly imported chloroplast proteins refolded and assembled into functional complexes? Findings: We found that Orf2971, encoded by the largest gene in the Chlamydomonas reinhardtii chloroplast genome and proposed to be an ortholog of Ycf2, is directly associated with the protein import machinery and plays a crucial role in ensuring the quality of proteins targeted to the chloroplast. Orf2971 deficiency induces protein precursor accumulation, partial proteolysis and protein aggregation, increased expression of chaperones and proteases, and autophagy. We hypothesize that Orf2971 is intimately linked to the protein import machinery and plays a critical role in chloroplast protein quality control. Next steps: The next challenge is to identify the sorting components associated with this complex on the stromal side. Furthermore, additional experimental evidence is required to investigate the relationship between different import machineries, including the analysis of the accumulation of precursor proteins in the various import mutants.     

“一带一路”地区生态系统服务关系的时空分异与区域响应

"一带一路"沿线多数发展中国家地处生态脆弱区,土地资源空间配置亟待优化。研究生态系统服务间的相互关系可以为土地利用决策提供定量化支持,但该关系在不同地域的表现形式有较大的差异性。基于InVEST模型,评估"一带一路"区域2000、2005、2010和2015年土壤保持、产水量、碳固定和生境质量4种生态系统服务时空变化,通过相关性分析和局部空间自相关分析等方法识别生态系统服务相互关系,以及其对不同地域特征变量的响应。就区域整体而言,土壤保持、产水量、碳固定和生境质量呈现中亚和西亚为一致低值区,而高值区分布不一致的空间格局;生态系统服务之间均呈显著协同关系,但冷热点格局的区域异质性显著。在生态区单元中,泰加林、温带草原和灌木的多种生态系统服务间为权衡关系;在国家单元中,生态系统服务间协同与权衡关系并存。产水量与碳固定间的协同关系对人口分布有良好的响应,而土壤保持与碳固定对人口分布的响应不明显。定量化评估生态系统服务及权衡关系,为区域土地资源优化配置提供依据,研究结果也为"一带一路"地区沿线国家间生态保护合作提供空间指引。     

Whole genome sequencing of Luxi Black Head sheep for screening selection signatures associated with important traits

ObjectiveLuxi Black Head sheep (LBH) is the first crossbreed specialized for meat production and was developed by crossbreeding Black Head Dorper sheep (DP) and Small Tailed Han sheep (STH) in the farming areas of northern China. Research on the genomic variations and selection signatures of LBH caused by continuous artificial selection is of great significance for identifying the genetic mechanisms of important traits of sheep and for the continuous breeding of LBH.MethodsWe explored the genetic relationships of LBH, DP, and several Mongolian sheep breeds by constructing phylogenetic tree, principal component analysis and linkage disequilibrium analysis. In addition, we analysed 29 whole genomes of sheep. The genome-wide selection signatures have been scanned with four methods: heterozygosity (H_P), fixation index (F_ST), cross-population extended haplotype homozygosity (XP-EHH) and the nucleotide diversity (θ_π) ratio.ResultsThe genetic relationships analysis showed that LBH appeared to be an independent cluster closer to DP. The candidate signatures of positive selection in sheep genome revealed candidate genes for developmental process (HoxA gene cluster, BCL2L11, TSHR), immunity (CXCL6, CXCL1, SKAP2, PTK6, MST1R), growth (PDGFD, FGF18, SRF, SOCS2), and reproduction (BCAS3, TRIM24, ASTL, FNDC3A). Moreover, two signalling pathways closely related to reproduction, the thyroid hormone signalling pathway and the oxytocin signalling pathway, were detected.ConclusionThe selective sweep analysis of LBH genome revealed candidate genes and signalling pathways associated with developmental process, immunity, growth, and reproduction. Our findings provide a valuable resource for sheep breeding and insight into the mechanisms of artificial selection.     

Angiotensin 1-7 and its analogue decrease blood pressure but aggravate renal damage in preeclamptic mice

Preeclampsia (PE) is a multisystem disease that affects the health of both the pregnant women and the fetus during pregnancy. Agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) play a significant role in the pathogenesis of PE. This study aimed to determine the effects of Angiotensin 1-7 (Ang 1-7) and its analogue AVE0991 on AT1-AA-induced PE model. Pregnant mice were divided into five groups: the normal pregnant group, AT1-AA-induced preeclampsia group, and AT1-AA-induced preeclampsia group treated with Losartan, Ang 1-7, and AVE0991, respectively. AT1-AA-induced PE model was established on gestational day 13 by tail intravenous injection of purified AT1-AA polyclonal antibody from serum of guinea pigs. Blood urea nitrogen (BUN), urine albumin and urinary creatinine were measured on day 18 of pregnancy. The systolic blood pressure (SBP) was measured from gestational day 13 to day 18. Renal structure changes were observed via light and electron microscopy. Compared with the normal pregnant group (NP group), AT1-AA-induced preeclampsia group (PE group) exhibited elevated blood pressure and proteinuria, consistent with the characteristics of PE. Ang 1-7 or AVE0991 treatment decreased blood pressure without showing renoprotective effects. The findings indicated that Ang 1-7 and its analogue reduced blood pressure but aggravated renal damage in AT1-AA-induced PE mice.     

Treatment of central type lung cancer by combined cryotherapy: Experiences of 47 patients

Most patients with central type lung cancer (CTLC) are not candidates for surgery; systemic chemotherapy and external beam radiotherapy are the main treatments but have not greatly affected patient outcome. Combined percutaneous and endobronchial cryotherapy has been used successfully to treat CTLC; this study aimed to determine its feasibility and safety. Forty-seven patients with unresectable CTLC (22 endotracheal, 26 tracheal wall and 21 extratracheal tumors) underwent 69 sessions of combined percutaneous cryosurgery, endobronchial cryosurgery and airway stenting. The long diameter of all tumors was <5 cm. Biopsy showed non-small cell lung cancer (NSCLC) in 40 patients (medium or well differentiated in 20 cases, poorly differentiated in 20) and small cell lung cancer (SCLC) in seven. Within 3 days after treatment, ventilatory capacity and performance status had obviously increased and cough, signs of dyspnea, hemoptysis and atelectasis improved significantly, but symptoms of pneumothorax and pleural effusion emerged. After 2 weeks, all complications had disappeared completely, as had cough. Progression-free survival (PFS) for endotracheal tumors (8 ± 4 months) was shorter than that for tracheal wall (13 ± 6 months, P < 0.05) and extratracheal (14 ± 8 months, P < 0.01) tumors. The PFS of NSCLC (11 ± 5 months) was significantly longer than that of SCLC (4 ± 2 months, P < 0.0001). The PFS of medium or well differentiated CTLC (15 ± 8 months) was significantly longer than that of poorly differentiated CTLC (7 ± 3 months, P < 0.0001). In conclusion, combined cryotherapy is a safe and effective treatment for CTLC, with PFS largely influenced by tumor location and pathologic type.     

A bacteria-induced, intracellular serpin in granular hemocytes of Manduca sexta.

Serine proteinase inhibitors from the serpin superfamily have been identified as hemolymph proteins from several groups of arthropods, including horseshoe crabs, crayfish, and insects. In the tobacco hornworm, Manduca sexta, one group of serpins present in plasma is generated by alternate exon splicing from serpin gene-1. We have identified a second serpin gene from this insect, M. sexta serpin-2. A serpin-2 DNA clone was isolated from a fifth instar larval cDNA library. The full-length cDNA is 1.5 kb long and encodes a protein of 381 amino acid residues. Amino acid sequence comparisons with other invertebrate serpins reveal approximately 25-40% identity with serpin-2. An expressed sequence tag from Bombyx mori, which is very similar to M. sexta serpin-2, was identified, and the corresponding full-length cDNA sequence was determined. This silkworm homolog of serpin-2 is 57% identical to M. sexta serpin-2. Recombinant M. sexta serpin-2 was used as an antigen to generate a rabbit polyclonal antiserum. This antiserum recognized a 43 kDa protein present in hemocytes but absent from plasma. Western and Northern blot results revealed that serpin-2 gene expression increased dramatically after larvae were injected with bacteria. In situ hybridization showed that the serpin-2 mRNA is present in granular hemocytes of immune-stimulated larvae. Serpin-2 purified from hemocytes obtained 24 h after injection of larvae with bacteria lacked inhibitory activity for all proteinases tested except for human cathepsin G. The intracellular location of serpin-2 suggests a function for serpin-2 different from the plasma serpin-1 proteins.