Heme utilization in the Caenorhabditis elegans hypodermal cells is facilitated by heme-responsive gene-2

The roundworm Caenorhabditis elegans is a heme auxotroph that requires the coordinated actions of HRG-1 heme permeases to transport environmental heme into the intestine and HRG-3, a secreted protein, to deliver intestinal heme to other tissues including the embryo. Here we show that heme homeostasis in the extraintestinal hypodermal tissue was facilitated by the transmembrane protein HRG-2. Systemic heme deficiency up-regulated hrg-2 mRNA expression over 200-fold in the main body hypodermal syncytium, hyp 7. HRG-2 is a type I membrane protein that binds heme and localizes to the endoplasmic reticulum and apical plasma membrane. Cytochrome heme profiles are aberrant in HRG-2-deficient worms, a phenotype that was partially suppressed by heme supplementation. A heme-deficient yeast strain, ectopically expressing worm HRG-2, revealed significantly improved growth at submicromolar concentrations of exogenous heme. Taken together, our results implicate HRG-2 as a facilitator of heme utilization in the Caenorhabditis elegans hypodermis and provide a mechanism for the regulation of heme homeostasis in an extraintestinal tissue.     

A liquid-based method for the assessment of bacterial pathogenicity using the nematode Caenorhabditis elegans

Caenorhabditis elegans has previously been used as an alternative to mammalian models of infection with bacterial pathogens. We have developed a liquid-based assay to measure the effect of bacteria on the feeding ability of C. elegans. Using this assay we have shown that Pseudomonas aeruginosa strain PA14, Burkholderia pseudomallei and Yersinia pestis were able to inhibit feeding of C. elegans strain N2. An increase in sensitivity of the assay was achieved by using C. elegans mutant phm-2, in place of the wild-type strain. Using this assay,P. aeruginosa PA01 inhibited the feeding of C. elegans mutant phm-2. Such liquid-based feeding assays are ideally suited to the high-throughput screening of mutants of bacterial pathogens.     

Caenorhabditis elegans Recognizes a Bacterial Quorum-sensing Signal Molecule through the AWCON Neuron

In a process known as quorum sensing, bacteria use chemicals called autoinducers for cell-cell communication. Population-wide detection of autoinducers enables bacteria to orchestrate collective behaviors. In the animal kingdom detection of chemicals is vital for success in locating food, finding hosts, and avoiding predators. This behavior, termed chemotaxis, is especially well studied in the nematode Caenorhabditis elegans. Here we demonstrate that the Vibrio cholerae autoinducer (S)-3-hydroxytridecan-4-one, termed CAI-1, influences chemotaxis in C. elegans. C. elegans prefers V. cholerae that produces CAI-1 over a V. cholerae mutant defective for CAI-1 production. The position of the CAI-1 ketone moiety is the key feature driving CAI-1-directed nematode behavior. CAI-1 is detected by the C. elegans amphid sensory neuron AWC^ON. Laser ablation of the AWC^ON cell, but not other amphid sensory neurons, abolished chemoattraction to CAI-1. These analyses define the structural features of a bacterial-produced signal and the nematode chemosensory neuron that permit cross-kingdom interaction.     

Multiple Molecular Forms of Acetylcholinesterase in the Nematode Caenorhabditis elegans

Abstract: Extracts of the nematode Caenorhabditis elegans contain five molecular forms of acetylcholinesterase (AChE) activity that can be separated by a combination of selective solubilization, velocity sedimentation, and ion-exchange chromatography. These are called form IA (5.2s), form IB (4.9.s), form II (6.7s), form III (11.3s), and form IV (13.0s). All except form III are present in significant amounts in rapidly prepared extracts and are probably native; form III is probably derived autolytically from form IV. Most of forms IA and IB can be solubilized by repeated extractions without detergent, whereas forms II, III, and IV require detergent for effective solubilization and may therefore be membrane-bound. High salt concentrations are not required for, and do not aid in, the solubilization of these forms. For all forms, molecular weights and frictional ratios have been estimated by a combination of gel permeation chromatography and velocity sedimentations in both H₂O and D₂O. The molecular weight estimates range from 83,000 to 357,000 and only form II shows extensive asymmetry. The separated forms have been characterized with respect to substrate affinity, substrate specificity, inhibitor sensitivity, thermal inactivation, and detergent sensitivity. Judging by these properties, C. elegans is like other invertebrates in that none of its cholinesterase forms resembles either the “true” or the “pseudo” cholinesterase of vertebrates. However, internal comparison of the C. elegans forms clearly distinguishes forms IA, III, and IV as a group from forms IB and II; the former are therefore designated “class A” forms, the latter “class B” forms. Genetic evidence indicates that separate genes control class A and class B forms, and that these two classes overlap functionally. Several factors, including kinetic properties, molecular asymmetry, molecular size, and solubility, all suggest that a molecular model of the multiple cholinesterase forms observed in vertebrate electric organs probably does not apply in C. elegans. Potential functional roles and subunit structures of the multiple AChE forms within each C. elegans class are discussed.     

A deuterohemin peptide extends lifespan and increases stress resistance in Caenorhabditis elegans

Abstract

This group has invented a novel deuterohemin containing peptide deuterohemin-AlaHisThrValGluLys (DhHP-6), which has various biological activities including protection of murine ischemia reperfusion injury, improving cell survival and preventing apoptosis. It was hypothesized that DhHP-6 is beneficial on the lifespan of Caenorhabditis elegans (C. elegans) and increases their resistance to heat and oxidative stress. C. elegans were treated with different concentrations of DhHP-6. Survival time and sensitivity to heat and paraquat were investigated. The data demonstrated that the mean survival time of C. elegans was significantly increased (p < 0.05) in the DhHP-6 treated group compared with the control group. The maximum lifespan was not affected by DhHP-6 treatment. DhHP-6 improved the survival rate of C. elegans in the acute heat stress (35°C) and rescued the C. elegans' sensitivity to paraquat in acute oxidative stress. Superoxide dismutase 3 (SOD-3) protein was up-regulated by DhHP-6 treatment. It was further demonstrated that stress resistance genes such as hsp-16.1, hsp-16.49 and sir-2.1 were regulated by DhHP-6. DAF-16 and SIR-2.1 genes are essential for the beneficial effect of DhHP-6. Therefore, the investigation into the beneficial effect of DhHP-6 on C. elegans' lifespan has the potential to develop novel drugs to prevent ageing.     

秀丽隐杆线虫在高校遗传学实验中的应用

秀丽隐杆线虫(Caenorhabditiselegans)是模式生物中的重要成员之一,因其实验成本低,实验周期短,非常适宜用于高校的遗传学实验教学中。线虫在实验教学中的使用,一方面可以有效地丰富高校实验教学的内容,另一方面也可以很好地激发学生的学习兴趣。本文介绍了线虫在遗传学实验教学中的应用实例,如生活周期观察、单因子杂交、单核苷酸多态性研究、RNA干扰(RNAi)实验等;对实验设置、操作要求、实验相关准备工作等进行了较为细致的描述,为线虫在高校遗传学实验教学中的应用提供了详实案例,可为线虫在高校遗传学实验或其他相关实验课程如细胞生物学实验、模式生物与发育生物学实验中的应用提供参考。     

Advance in research of microRNA in Caenorhabditis elegans

microRNA (miRNA) is a family of small, non‐coding RNA first discovered as an important regulator of development in Caenorhabditis elegans (C. elegans). Numerous miRNAs have been found in C. elegans, and some of them are well conserved in many organisms. Though, the biologic function of miRNAs in C. elegans was largely unknown, more and more studies support the idea that miRNA is an important molecular for C. elegans. In this review, we revisit the research progress of miRNAs in C. elegans related with development, aging, cancer, and neurodegenerative diseases and compared the function of miRNAs between C. elegans and human. J. Cell. Biochem. 114: 994–1000, 2013. © 2012 Wiley Periodicals, Inc.     

Variation in Caenorhabditis elegans dauer larva formation

Dauer larvae of Caenorhabditis elegans are formed when young larvae experience conditions of low food availability and high conspecific population density; non-dauer, third stage larvae are formed in conditions of plenty. This developmental response to environmental conditions is an example of phenotypic plasticity; that is, an environmentally induced change in phenotype and, as such, a manifestation of a genotype-environment interaction. Extensive variation was found in reaction norms of phenotypic plasticity of dauer formation among wild lines of C. elegans. Recombinant-inbred lines were constructed from parental lines with very different reaction norms of dauer formation. These recombinant-inbred lines had a wide range of reaction norms, of a range greater than that set by the parental lines. The natural variation in reaction norms of dauer formation in C. elegans is, presumably, an adaptation to enhance fitness under the lines' different natural prevailing conditions. The genetic basis of this variation, as well as its phenotypic consequences, are now ripe for further investigation.     

Expanded polyglutamines impair synaptic transmission and ubiquitin-proteasome system in Caenorhabditis elegans

Polyglutamine (polyQ) expansion in many proteins, including huntingtin and ataxin-3, is pathogenic and responsible for neuronal dysfunction and degeneration. Although at least nine neurodegenerative diseases are caused by expanded polyQ, the pathogenesis of these diseases is still not well understood. In the present study, we used Caenorhabditis elegans to study the molecular mechanism of polyQ-mediated toxicity. We expressed full-length and truncated ataxin-3 with different lengths of polyQ in the nervous system of C. elegans. We show that expanded polyQ interrupts synaptic transmission, and induces swelling and aberrant branching of neuronal processes. Using an ubiquitinated fluorescence reporter construct, we also showed that polyQ aggregates impair the ubiquitin-proteasome system in C. elegans. These results may provide information for further understanding the pathogenesis of polyQ diseases.     

以秀丽线虫为模式生物评价蓖麻碱毒性的研究

以秀丽线虫作为评价蓖麻碱毒性的模式生物,通过测定不同浓度的蓖麻碱提取物对线虫的半致死浓度、生殖能力和体内酶活性的影响,对蓖麻碱的毒性进行初步评价。结果表明,蓖麻碱提取物的48h的LD50为0.977mg/mL,72h的LD50为0.821mg/mL;随着蓖麻碱提取物浓度从0.5mg/mL增加到2.0mg/mL,虫体的SOD活性由(80.669±3.2)U/mg降低至(1.532±0.2)U/mg;CAT活性由(70.947±2.7)U/mg降低至(0.234±2.1)U/mg。说明蓖麻碱提取物浓度越大,毒性越强,线虫体内酶活越低,蓖麻碱提取物可使秀丽线虫生殖能力降低或丧失。     

Caenorhabditis elegans functional genomics: omic resonance.

The nematode Caenorhabditis elegans is widely used as a model organism for studying many fundamental aspects of development and cell biology, including processes underlying human disease. The genome of C. elegans encodes over 19,000 protein-coding genes and hundreds of non-coding RNAs. The availability of whole genome sequence has facilitated the development of high throughput techniques for elucidating the function of individual genes and gene products. Furthermore, attempts can now be made to integrate these substantial functional genomics data collections and to understand at a global level how the flow of genomic information that is at the core of the central dogma leads to the development of a multicellular organism.     

Pyruvate imbalance mediates metabolic reprogramming and mimics lifespan extension by dietary restriction in Caenorhabditis elegans

Dietary restriction (DR) is the most universal intervention known to extend animal lifespan. DR also prevents tumor development in mammals, and this effect requires the tumor suppressor PTEN. However, the metabolic and cellular processes that underly the beneficial effects of DR are poorly understood. We identified slcf‐1 in an RNAi screen for genes that extend Caenorhabditis elegans lifespan in a PTEN/daf‐18‐dependent manner. We showed that slcf‐1 mutation, which increases average lifespan by 40%, mimics DR in worms fed ad libitum. An NMR‐based metabolomic characterization of slcf‐1 mutants revealed lower lipid levels compared to wild‐type animals, as expected for dietary‐restricted animals, but also higher pyruvate content. Epistasis experiments and metabolic measurements support a model in which the long lifespan of slcf‐1 mutants relies on increased mitochondrial pyruvate metabolism coupled to an adaptive response to oxidative stress. This response requires DAF‐18/PTEN and the previously identified DR effectors PHA‐4/FOXA, HSF‐1/HSF1, SIR‐2.1/SIRT‐1, and AMPK/AAK‐2. Overall, our data show that pyruvate homeostasis plays a central role in lifespan control in C. elegans and that the beneficial effects of DR results from a hormetic mechanism involving the mitochondria. Analysis of the SLCF‐1 protein sequence predicts that slcf‐1 encodes a plasma membrane transporter belonging to the conserved monocarboxylate transporter family. These findings suggest that inhibition of this transporter homolog in mammals might also promote a DR response.     

食细菌线虫Caenorhabditis elegans的取食偏好性

通过设置平板培养试验,以模式种线虫 Caenorhabditis elegans 为材料,观察了食细菌线虫的取食行为。结果表明：C. elegans 在取食细菌时对原位土壤中分离的一种Pseudomonas sp细菌存在最大的取食偏好性。这种取食偏好性表现在大部分C. elegans 在24 h内都直接朝Pseudomonas sp迁移,说明C. elegans能通过某种机制识别Pseudomonas sp。距离迁移试验及C. elegans迁移率表明它可能是通过辨别细菌所发出的气味识别它喜欢的食物。C. elegans的繁殖率跟其取食的偏好性是相关的,在迁移率较高的细菌培养基中线虫表现出更高的繁殖率。结果还表明：相对于G+细菌而言, C. elegans 偏好取食G-细菌。为进一步了解土壤生态系统中食细菌线虫与细菌群落结构间相互关系提供了帮助。     

Genetic variation for outcrossing among Caenorhabditis elegans isolates

The evolution of breeding systems results from the existence of genetic variation and selective forces favoring different outcrossing rates. In this study we determine the extent of genetic variation for characters directly related to outcrossing, such as male frequency, male mating ability, and male reproductive success, in several wild isolates of the nematode Caenorhabditis elegans. This species is characterized by an androdioecious breeding system in which males occur with hermaphrodites that can either self-fertilize or outcross with males. We find genetic variation for all characters measured, but also find that environmental variation is a large fraction of the total phenotypic variance. We further determine the existence of substantial genetic variation for population competitive performance in several laboratory environments. However, these measures are uncorrelated with outcrossing characters. The data presented here contribute to an understanding of male maintenance in natural populations through their role in outcrossing.     

必需氨基酸延缓秀丽隐杆线虫衰老的研究

利用模式生物秀丽隐杆线虫,考察8种人体必需氨基酸对衰老的影响。首先建立秀丽隐杆线虫寿命模型,以雷帕霉素为阳性对照药,分别考察8种必需氨基酸对线虫生存时间的影响。再用筛选出的氨基酸处理线虫21d,通过秀丽隐杆线虫-绿脓杆菌感染模型,考察氨基酸对线虫的抗感染能力的影响,利用实时荧光定量Real-Time RT-PCR方法检测氨基酸处理线虫后DAF-16/FOXO下游基因和免疫相关基因的表达水平。结果表明8种必需氨基酸中苏氨酸和异亮氨酸既能延长野生型线虫的寿命又能延长daf-16突变型线虫的寿命,同时还能增强秀丽隐杆线虫抗绿脓杆菌感染的能力,并提高免疫相关基因lys-7、clec-67的表达水平,而DAF-16/FOXO下游基因表达没有明显变化。因此苏氨酸和异亮氨酸能延长线虫寿命、提高抗感染能力,且对线虫寿命的延长作用不完全依赖于DAF-16/FOXO转录因子。     

细菌与秀丽隐杆线虫之间互作关系的研究进展

秀丽隐杆线虫(Caenorhabditis elegans)以其个体小、易培养、生活周期短等优势成为生物发育、衰老、神经及免疫相关机制研究的模式生物.它在实验室培养时主要靠饲喂大肠杆菌OP50,有报道,细菌及其代谢物对线虫的代谢、行为和寿命有至关重要的影响.因此,作为一个遗传模型,秀丽隐杆线虫可以帮助研究微生物与宿主相...     

线虫(Caenorhabditis elegans)基因组的研究进展

线虫（Ｃａｅｎｏｒｈａｂｄｉｔｉｓ ｅｌｅｇａｎｓ）是重要的模式生物,其基因组序列分析工作于１９９８年底基本完成,已有１９０００多个基因被鉴定。本文概述线虫基因组研究中遗传图谱、物理图谱、序列测定和基因识别等方面的研究成果,以及线虫基因组计划将对生命科学研究产生的影响。     

A novel alpha1,2-fucosyltransferase (CE2FT-2) in Caenorhabditis elegans generates H-type 3 glycan structures

The 1,2-fucosyltransferase family (1,2FT) is the largest familyof glycosyltransferases in the genome of the free-living nematodeCaenorhabditis elegans, and early evidence suggests that eachmember may have a unique activity. Here we describe a C. elegansgene (designated CE2FT-2) encoding an 1,2FT that has the potentialto generate the sequence Fuc1-2Galβ1-3GalNAc-R, which isthe H-type 3 blood group structure. The CE2FT-2 cDNA encodesa putative transmembrane protein that shows 42% amino acid identityto a previously cloned C. elegans 1,2FT (termed CE2FT-1), buthas a very low identity (16–20%) to 1,2FT sequences inhumans, rabbits, and mice. A recombinant form of CE2FT-2 expressedin human 293T cells has a high 1,2FT activity toward Galβ1-3GalNAc-O-pNP,but unexpectedly, the enzyme is inactive toward the acceptorGalβ-O-phenyl. Thus, CE2FT-2 differs from all other 1,2FTspreviously described from animals that all utilize Galβ-O-phenyl.CE2FT-2 is expressed at all stages of worm development, butremarkably, promoter analysis of the CE2FT-2 gene using greenfluorescent protein reporter constructs indicates that the CE2FT-2is expressed exclusively in pharyngeal cells of the worm fromembryo to an adult stage. Because pharyngeal cells are knownto secrete their glycoconjugates to the nematode surface, theseresults may indicate that products of CE2FT-2 contribute tointeractions of the nematode with its environment or are usedas ligands for bacterial attachment. These findings, along withthose on other 1,2FTs in C. elegans, suggest that each 1,2FTin this organism may have a unique acceptor specificity, expressionpattern, and biological function.