Nitrogen deprivation in Fusarium oxysporum promotes mycotoxin production via intermediates in the Krebs cycle and unreported methylmalonyl-CoA mutase activity

Metabolomics - The identification of metabolomic dysregulation appears promising for the prediction of type 1 diabetes and may also reveal metabolic pathways leading to beta-cell destruction....     

Vandachostylis ‘Sri-Siam’: an intergeneric hybrid with superior qualities as evidenced by its biochemical fragrance and transcriptome profiles

Journal of Plant Biochemistry and Biotechnology - Vandachostylis ‘Sri-Siam’ is a fragrant orchid, suitable as a potted plant for the floriculture and perfumery industries due to its...     

Diet-Induced Over-Expression of Flightless-I Protein and Its Relation to Flightlessness in Mediterranean Fruit Fly,Ceratitis capitata

The Mediterranean fruit fly (medfly), Ceratitis capitata is among the most economically important pests worldwide. Understanding nutritional requirement helps rearing healthy medfly for biocontrol of its population in fields. Flight ability is a high priority criterion. Two groups of medfly larvae were reared with two identical component diets except one with fatty acids (diet A) and another without it (diet B). Adults from larvae reared on diet B demonstrated 20±8% of normal flight ability, whereas those from larvae reared on diet A displayed full flight ability of 97±1%. Proteomes were profiled to compare two groups of medfly pupae using shotgun proteomics to study dietary effects on flight ability. When proteins detected in pupae A were compared with those in pupae B, 233 and 239 proteins were, respectively, under- and over-expressed in pupae B, while 167 proteins were overlapped in both pupae A and B. Differential protein profiles indicate that nutritional deficiency induced over-expression of flightless-I protein (fli-I) in medfly. All proteins were subjected to Ingenuity Pathway Analysis (IPA) to create 13 biological networks and 17 pathways of interacting protein clusters in human ortholog. Fli-I, leucine-rich repeat (LRR)-containing G protein-coupled receptor 2, LRR protein soc-2 and protein wings apart-like were over-expressed in pupae B. Inositol-1,4,5-trisphosphate receptor, protocadherin-like wing polarity protein stan and several Wnt pathway proteins were under-expressed in pupae B. These results suggest down-regulation of the Wnt/wingless signaling pathway, which consequently may result in flightlessness in pupae B. The fli-I gene is known to be located within the Smith-Magenis syndrome (SMS) region on chromosome 17, and thus, we speculate that nutritional deficiency might induce over-expression of fli-I (or fli-I gene) and be associated with human SMS. However, more evidence would be needed to confirm our speculation.     

Increase of anti-HIV activity of C-peptide fusion inhibitors using a bivalent drug design approach

We reported the design of fusion inhibitors with improved activity using a multivalent inhibitor design strategy. First, we chose C29 as the template sequence, which is a 29-mer peptide derived from HIV-1 gp41 CHR domain and has anti-HIV activity of IC₅₀ 118 nM in a cell–cell fusion assay. We optimized the crosslink sites and linkers of the template peptide. We found that N-terminal crosslink caused activity improvement based on the multivalent co-operative effect. Especially, the IC₅₀ of peptide (CAcaC29)₂ was improved from 49.02 (monomeric form) to 5.71 nM. Compared with long peptides, short peptides may be more suitable to analyze the co-operative effect. So we selected a shorter peptide C22 to synthesize the bivalent inhibitors. Due its weak helicity, no co-operative effect appeared. Therefore, we chose SC22EK, which were introduced salt bridges to consolidate the helicity based on the natural sequence C22. The cross-linked (CAcaSC22EK)₂ was four times more potent than the monomer SC22EK in anti-HIV activity, with an IC₅₀ value of 4.92 nM close to the high active peptide fusion inhibitor C34. The strategy used in this study may be used to design new fusion inhibitors to interfere similar processes.     

Genetic Variants in Meiotic Program Initiation Pathway Genes Are Associated with Spermatogenic Impairment in a Han Chinese Population

Background

The meiotic program initiation pathway genes (CYP26B1, NANOS1 and STRA8) have been proposed to play key roles in spermatogenesis.

Objective

To elucidate the exact role of the genetic variants of the meiosis initiation genes in spermatogenesis, we genotyped the potential functional genetic variants of CYP26B1, NANOS1 and STRA8 genes, and evaluated their effects on spermatogenesis in our study population.

Design, Setting, and Participants

In this study, all subjects were volunteers from the affiliated hospitals of Nanjing Medical University between March 2004 and July 2009 (NJMU Infertile Study). Total 719 idiopathic infertile cases were recruited and divided into three groups according to WHO semen parameters: 201 azoospermia patients (no sperm in the ejaculate even after centrifugation), 155 oligozoospermia patients (sperm counts <20×10⁶/ml) and 363 infertility/normozoospermia subjects (sperm counts >20×10⁶/ml). The control group consisted of 383 subjects with normal semen parameters, all of which had fathered at least one child without assisted reproductive technologies.

Measurements

Eight single nucleotide polymorphisms (SNPs) in CYP26B1, NANOS1 and STRA8 genes were determined by TaqMan allelic discrimination assay in 719 idiopathic infertile men and 383 healthy controls.

Results and Limitations

The genetic variant rs10269148 of STRA8 gene showed higher risk of spermatogenic impairment in the groups of abnormospermia (including azoospermia subgroup and oligozoospermia subgroup) and azoospermia than the controls with odds ratios and 95% confidence intervals of 2.52 (1.29–4.94) and 2.92 (1.41–6.06), respectively (P = 0.006, 0.002 respective). Notably, larger sample size studies and in vivo or in vitro functional studies are needed to substantiate the biological roles of these variants.

Conclusions

Our results provided epidemiological evidence supporting the involvement of genetic polymorphisms of the meiotic program initiation genes in modifying the risk of azoospermia and oligozoospermia in a Han-Chinese population.     

Biochemical evidence for an editing role of thioesterase II in the biosynthesis of the polyketide pikromycin

The pikromycin biosynthetic gene cluster contains the pikAV gene encoding a type II thioesterase (TEII). TEII is not responsible for polyketide termination and cyclization, and its biosynthetic role has been unclear. During polyketide biosynthesis, extender units such as methylmalonyl acyl carrier protein (ACP) may prematurely decarboxylate to generate the corresponding acyl-ACP, which cannot be used as a substrate in the condensing reaction by the corresponding ketosynthase domain, rendering the polyketide synthase module inactive. It has been proposed that TEII may serve as an "editing" enzyme and reactivate these modules by removing acyl moieties attached to ACP domains. Using a purified recombinant TEII we have tested this hypothesis by using in vitro enzyme assays and a range of acyl-ACP, malonyl-ACP, and methylmalonyl-ACP substrates derived from either PikAIII or the loading didomain of DEBS1 (6-deoxyerythronolide B synthase; AT(L)-ACP(L)). The pikromycin TEII exhibited high K(m) values (>100 microm) with all substrates and no apparent ACP specificity, catalyzing cleavage of methylmalonyl-ACP from both AT(L)-ACP(L) (k(cat)/K(m) 3.3 +/- 1.1 m(-1) s(-1)) and PikAIII (k(cat)/K(m) 2.9 +/- 0.9 m(-1) s(-1)). The TEII exhibited some acyl-group specificity, catalyzing hydrolysis of propionyl (k(cat)/K(m) 15.8 +/- 1.8 m(-1) s(-1)) and butyryl (k(cat)/K(m) 17.5 +/- 2.1 m(-1) s(-1)) derivatives of AT(L)-ACP(L) faster than acetyl (k(cat)/K(m) 4.9 +/- 0.7 m(-1) s(-1)), malonyl (k(cat)/K(m) 3.9 +/- 0.5 m(-1) s(-1)), or methylmalonyl derivatives. PikAIV containing a TEI domain catalyzed cleavage of propionyl derivative of AT(L)-ACP(L) at a dramatically lower rate than TEII. These results provide the first unequivocal in vitro evidence that TEII can hydrolyze acyl-ACP thioesters and a model for the action of TEII in which the enzyme remains primarily dissociated from the polyketide synthase, preferentially removing aberrant acyl-ACP species with long half-lives. The lack of rigorous substrate specificity for TEII may explain the surprising observation that high level expression of the protein in Streptomyces venezuelae leads to significant (>50%) titer decreases.     

Crystal structures of aprotinin and its complex with sucrose octasulfate reveal multiple modes of interactions with implications for heparin binding

The crystal structures of aprotinin and its complex with sucrose octasulfate (SOS), a polysulfated heparin analog, were determined at 1.7-2.6 Å resolutions. Aprotinin is monomeric in solution, which associates into a decamer at high salt concentrations. Sulfate ions serve to neutralize the basic amino acid residues of aprotinin to stabilize the decameric aprotinin. Whereas SOS interacts with heparin binding proteins at 1:1 molar ratio, SOS was surprisingly found to induce strong agglutination of aprotinins. Five molecules of aprotinin interact with one molecule of the sulfated sugar, which is stabilized by electrostatic interactions between the positively charged residues of aprotinin and sulfate groups of SOS. The multiple binding modes of SOS with five individual aprotinin molecules may represent the diverse patterns of potential heparin binding to aprotinin, reflecting the interactions of densely packed protein molecules along the heparin polymer.     

红火蚁入侵对玉米地蜘蛛类群多样性的影响

采用陷阱法和目测法系统研究了红火蚁入侵玉米地对蜘蛛类群多样性的影响.期间共调查到蜘蛛8科16种,其中红火蚁发生区有6科10种,药防区4科5种,对照区8科11种;蜘蛛种类以游猎型为主,隶属于猫蛛科和跳蛛科,优势种包括斜纹猫蛛、乔氏蚁蛛和蚁蛛.在红火蚁发生区,从玉米心叶后期开始红火蚁种群数量不断增加,在玉米抽穗开花期达到最大,为225头,之后缓慢降低,相应的猫蛛属蜘蛛种群数量则逐渐降低,降幅达79.2％;而蚁蛛属蜘蛛的种群数量变化不大.随着玉米植株的生长,红火蚁发生区和药防区的蜘蛛种类、多样性指数和均匀度指数逐渐降低,生态优势度指数却不断升高,而对照区相关指标则相反.表明红火蚁入侵显著改变了玉米地蜘蛛的类群结构.     

CFTR mediates bicarbonate-dependent activation of miR-125b in preimplantation embryo development

Although HCO₃⁻ is known to be required for early embryo development, its exact role remains elusive. Here we report that HCO₃⁻ acts as an environmental cue in regulating miR-125b expression through CFTR-mediated influx during preimplantation embryo development. The results show that the effect of HCO₃⁻ on preimplantation embryo development can be suppressed by interfering the function of a HCO₃⁻-conducting channel, CFTR, by a specific inhibitor or gene knockout. Removal of extracellular HCO₃⁻ or inhibition of CFTR reduces miR-125b expression in 2 cell-stage mouse embryos. Knockdown of miR-125b mimics the effect of HCO₃⁻ removal and CFTR inhibition, while injection of miR-125b precursor reverses it. Downregulation of miR-125b upregulates p53 cascade in both human and mouse embryos. The activation of miR-125b is shown to be mediated by sAC/PKA-dependent nuclear shuttling of NF-κB. These results have revealed a critical role of CFTR in signal transduction linking the environmental HCO₃⁻ to activation of miR-125b during preimplantation embryo development and indicated the importance of ion channels in regulation of miRNAs.