Characterization of the lipid-carrier involved in the synthesis of enterobacterial common antigen (ECA) and identification of a novel phosphoglyceride in a mutant of Salmonella typhimurium defective in ECA synthesis

The polysaccharide chains of enterobacterial common antigen (ECA) consist of linear trisaccharide repeat units with the structure -->3)- alpha-d-Fuc4NAc-(1-->4)-beta-d-ManNAcA-(1--> 4)-alpha-d-GlcNAc-(1-->, where Fuc4NAc is 4-acetamido-4, 6-dideoxy-d-galactose, ManNAcA is N - acetyl-d- mannosaminuronic acid, and GlcNAc is N -acetyl-d-glucosamine. The major form of ECA (ECAPG) consists of polysaccharide chains that are believed to be covalently linked to diacylglycerol through phosphodiester linkage; the phospholipid moiety functions to anchor molecules in the outer membrane. The ECA trisaccharide repeat unit is assembled as a polyisoprenyl-linked intermediate which has been tentatively identified as Fuc4NAc-ManNAcA-GlcNAc- pyrophosphorylundecaprenol (lipid III). Subsequent chain-elongation presumably occurs by a block-polymerization mechanism. However, the identity of the polyisoprenoid carrier-lipid has not been established. Accordingly, the current studies were conducted in an effort to structurally characterize the polyisoprenyl lipid-carrier involved in ECA synthesis. Isolation and characterization of the lipid carrier was facilitated by the accumulation of a ManNAcA-GlcNAc- pyrophosphorylpolyisoprenyl lipid (lipid II) in mutants of Salmonella typhimurium defective in the synthesis of TDP-Fuc4NAc, the donor of Fuc4NAc residues for ECA synthesis. Analyses of lipid II preparations by fast atom bombardment tandem mass spectroscopy (FAB-MS/MS) resulted in the identification of the lipid-carrier as the 55-carbon polyisoprenyl alcohol, undecaprenol. These analyses also resulted in the identification of a novel glycolipid which copurified with lipid II. FAB-MS/MS analyses of this glycolipid revealed its structure to be 1,2-diacyl- sn -glycero-3-pryophosphoryl-GlcNAc-ManNAcA (DGP- disaccharide). An examination of purified ECAPGby phosphorus-31 nuclear magnetic resonance spectroscopy confirmed that the polysaccharide chains are linked to diacylglycerol through phosphodiester linkage. Thus, DGP-disaccharide does not appear to be an intermediate in ECAPGsynthesis. Nevertheless, although the available evidence clearly indicate that lipid II is a precursor of DGP-disaccharide, the function of this novel glycolipid is not yet known, and it may be an intermediate in the biosynthesis of a molecule other than ECAPG.      

游仆虫信息素Er-1和Er-2对四膜虫的种间作用

信息素是生物体向外释放的化学物质,在细胞及生物体中具有种内信息传递的生理学功能。信息素这一类分子广泛分布于系统发生史中,它们的特异活性在单细胞生物、昆虫以及脊椎动物中均有报道。脊椎动物中信息素的信号传输已被证实是一嗅觉依赖过程,7TM-受体被认为是信号传输过程中的信号转换器。在低等单细胞生物(例如:来可夫游仆虫)的细胞膜上存在有信息素异构体,作为信息素分子的有效结合位点而行使其功能。本研究主要探讨单细胞的信息素(Er-1和Er-2)的基础细胞生理学作用是仅限于产生该信息素的物种,还是对其它的原生动物(例如:四膜虫)或对系统发育中分类地位较高的细胞(例如:MRC5成纤维细胞或J774巨噬细胞)均具有调节活性。研究结果表明,游仆虫的两种信息素对梨形四膜虫GL的生长调节有显著不同的作用:当信息素浓度为10-11M时,Er-1具有正调控作用,而Er-2具有抑制剂的作用。这两种配体的趋化作用也有很不同:Er-1具有一种广范的化学排斥特性,而Er-2具有一个双峰的化学吸引剂的性质。计算机检测发现,与Er-2的作用不同,Er-1可略微降低被测细胞的游动速率。趋化现象的选择特性表明Er-2信息素的受体有一种“短期”的特性;而Er-1是不能选择任何亚种群的,这也支持了我们先前的研究数据,即这两种信息素在四膜虫GL内产生两种不同的信号。四膜虫对信息素特异性的反应表明四膜虫能辨别非常近似但带有微小差异的配体(如Er-1和Er-2的电荷差异)。     

Concerted transpositions of mobile genetic elements coupled with fitness changes in Drosophila melanogaster

In an inbred low-activity (LA) strain of Drosophila melanogaster with a low level of fitness and a complex of inadaptive characters, in situ hybridization reveals an invariant pattern of distribution of three copia-like elements (mdg-1, mdg-3, and copia). Rare, spontaneous, multiple transpositions of mobile elements in the LA strain were shown to be coupled with a drastic increase of fitness. A changed pattern of various types of mobile elements was also observed on selecting the LA strain for higher fitness. High-fitness strains show transpositions of mobile elements to definite chromosomal sites ("hot spots"). Concerted changes in the location of three different mobile elements were found to be coupled with an increase of fitness. The mdg-1 distribution patterns were also examined in two low-fitness strains independently selected from the high-fitness ones. Fitness decrease was accompanied by mdg-1 excision from the hot spots of their location usually detected in the high-fitness strains. The results suggest the existence of a system of adaptive transpositions of mobile elements that takes part in fitness control.      

Stable wheat transformation obtained without selectable markers

Transgenic wheat plants without the selectable marker gene were obtained either in the presence or in the absence of selective pressure during the transformation protocol. When using hygromycin as selective agent in a co-transformation experiment involving a mixture of plasmids pGL2, containing the hpt gene, and pAI₁Gus, containing the uidA gene, 3 out of 19 transgenic wheat plants had the uidA gene alone as shown by Southern blots. The gene was transmitted to the progeny following Mendelian rules. Segregation and loss of the selectable marker gene was also found in three out of six events from other experiments where high-molecular-weight glutenin genes were expressed or over-expressed. On the other hand, in 7 experiments where no selective pressure was applied and that involved 1016 bombarded explants, 23 transgenic wheat plants were obtained. The uidA gene was stably integrated as suggested by its transmission to the progeny.these authors contributed equally to the work     

Expressed sequence tag analysis and development of gene associated markers in a near-isogenic plant system of Eragrostis curvula

Eragrostis curvula (Schrad.) Nees is a forage grass native to the semiarid regions of Southern Africa, which reproduces mainly by pseudogamous diplosporous apomixis. A collection of ESTs was generated from four cDNA libraries, three of them obtained from panicles of near-isogenic lines with different ploidy levels and reproductive modes, and one obtained from 12 days-old plant leaves. A total of 12,295 high-quality ESTs were clustered and assembled, rendering 8,864 unigenes, including 1,490 contigs and 7,394 singletons, with a genome coverage of 22%. A total of 7,029 (79.11%) unigenes were functionally categorized by BLASTX analysis against sequences deposited in public databases, but only 37.80% could be classified according to Gene Ontology. Sequence comparison against the cereals genes indexes (GI) revealed 50% significant hits. A total of 254 EST-SSRs were detected from 219 singletons and 35 from contigs. Di- and tri- motifs were similarly represented with percentages of 38.95 and 40.16%, respectively. In addition, 190 SNPs and Indels were detected in 18 contigs generated from 3 to 4 libraries. The ESTs and the molecular markers obtained in this study will provide valuable resources for a wide range of applications including gene identification, genetic mapping, cultivar identification, analysis of genetic diversity, phenotype mapping and marker assisted selection.     

An appraisal of the fossil record for the Cirolanidae (Malacostraca: Peracarida: Isopoda: Cymothoida), with a description of a new cirolanid isopod crustacean from the early Miocene of the Vienna Basin (Western Carpathians)

Abstract:  Isopod crustaceans are rarely preserved in the fossil record. Herein, an appraisal of the fossil record for the cirolanid isopods is presented. Five genera are briefly discussed, including Bathynomus, Brunnaega, Palaega, Pseudopalaega and Cirolana. A key for the cirolanid genera known to date from the fossil record is provided based mostly on pleotelson characters. From the early Miocene of the Slovak part of the Vienna Basin, Cirolana feldmanni sp. nov. is described being only the fifth fossil Cirolana species known to date and one of the few with preserved appendages. The material exhibits preservation suggesting biphasic moulting; the mode of preservation suggests a rather short time between shedding the posterior and anterior parts of the exoskeleton instead of hours or even days known in extant taxa. As no subsequent transport or physical disturbance was inferred, the specimens can be stated as in situ preservation. From the palaeoecological point of view, it is concluded that Cirolana feldmanni sp. nov. is the first unequivocal fossil deep‐water Cirolana as suggested by the accompanied fauna.     

Seed characteristics and fatty acid composition of castor (<i>Ricinus communis</i> L.) varieties in Northeast China

Oil content and fatty acid composition were investigated on 12 castor varieties and strains by using the soxhlet extraction method and capillary gas chromatography. This was made to provide a reference and theoretical basis for castorbean breeding with high oil content, determine variability of seed compounds for breeding purposes, and broaden chemical material choices. Results revealed that crude fat percentage in seeds ranged from 18.91 to 35.84% with an average of 25.91%; the absolute content of ricinoleic acid varied between 171.65 g/kg and 314.03 g/kg with an average of 222.43 g/kg, and kernel crude fat percentage was between 24.28 and 46.97% with an average of 34.30%. All these study variables were highest in the 2129 strain. The percentage of ricinoleic acid in crude fat was between 83.85 to 87.62%, and the highest value was found in the zhebi4 accession. The other fatty acids appeared in small concentrations, and showed small amplitude: 1.12 to 1.61%, 1.21 to 1.61%, 3.53 to 4.80%, 5.35 to 6.38%, 0.52 to 0.79%, 0.05 to 0.08% and 0.43 to 0.55%, for palmitic, stearic, oleic, linolic, linolenic, arachidic, and arachidonic acids, respectively. One hundred seed weight was determined for each accession. One hundred seed weight ranged from 25.7 g to 34.0 g with an average of 29.9 g. There was a significant correlation between seed weight and oil content, but the correlation value was low (r=0.51). Cluster analysis by SSPS based on the content of fatty acid composition revealed that the accessions were divided into three independent clusters. These findings will clearly provide useful information for further research in breeding and utilization of castor oil.     

骨形成蛋白(BMP)-2/4，-5与IA型BMP受体在口腔正常上皮、良性病变及癌变中的表达分析

认识BMP及其受体与口腔正常上皮及其癌变的关系。有助于深入了解口腔上皮癌变的机理。本文用免疫组织化学方法对BMP-2/4,-5与BMPR-IA在口腔颊部粘膜正常上皮,良性病变和癌变中的表达进行观察和半定量分析。标本包括：9例正常上皮（normal buccal muosa,NB)。8例慢性炎症（nonspecific chronic inflammation,NCI),7例过度角化（hyperkeratosis,HK)。5例乳头状瘤（squamous cell papilloma,SCP)。29例鳞癌（squamous cell carcinoma,SCC)。10例癌旁上皮（epithelium immediately adjacent to carcinoma,EAC)以及6例硬腭粘膜上皮（normal mucosa of hard palate,NHP）。结果显示：BMP-2/4,-5与BMPR-IA在口腔粘膜的正常与良性病变上皮中有弱的和不均一的阳性表达,NB与NHP无明显差别,而除3例SCC外,其它SCC几乎均有程度不一的阳性表达,在EAC中的表达接近于SCC,二者明显高于正常与良性组,此外,转移在淋巴结中的癌细胞的BMP-2/4与BMP-5阳性程度略高于原发灶的癌细胞,本文认为;BMP-2/4,5与BMPR-IA可能参与调控口腔上皮的癌变。