Characterization of a Gene Coding for the Complement System Component FB from Loxosceles laeta Spider Venom Glands

The human complement system is composed of more than 30 proteins and many of these have conserved domains that allow tracing the phylogenetic evolution. The complement system seems to be initiated with the appearance of C3 and factor B (FB), the only components found in some protostomes and cnidarians, suggesting that the alternative pathway is the most ancient. Here, we present the characterization of an arachnid homologue of the human complement component FB from the spider Loxosceles laeta. This homologue, named Lox-FB, was identified from a total RNA L. laeta spider venom gland library and was amplified using RACE-PCR techniques and specific primers. Analysis of the deduced amino acid sequence and the domain structure showed significant similarity to the vertebrate and invertebrate FB/C2 family proteins. Lox-FB has a classical domain organization composed of a control complement protein domain (CCP), a von Willebrand Factor domain (vWFA), and a serine protease domain (SP). The amino acids involved in Mg²⁺ metal ion dependent adhesion site (MIDAS) found in the vWFA domain in the vertebrate C2/FB proteins are well conserved; however, the classic catalytic triad present in the serine protease domain is not conserved in Lox-FB. Similarity and phylogenetic analyses indicated that Lox-FB shares a major identity (43%) and has a close evolutionary relationship with the third isoform of FB-like protein (FB-3) from the jumping spider Hasarius adansoni belonging to the Family Salcitidae.     

泥炭藓植物数量分类的研究

本文用聚类分析和主成分分析方法对泥炭藓属的14个种及一个变种进行了数量分类的研究。通过对15个OTU×42个性状的原始数值矩阵的标准化及复杂运算后,其结果表明:1.由聚类过程所得到的树系图,并结合生物分类学的实际意义,将泥炭藓属分为6个组,即Section Sphagnum、Sect.Squarrosa、Sect.Acutifolia、Sect.Subse-cunda、Sect.Polyclada及Sect.Cuspidata。其结果与经典分类的结果基本上是一致的。2.通过对泥炭藓主要性状的因子分析和主成分排序,初步反映了各性状所占的信息比例,找出了泥炭藓植物分类中所应依据的重要性状。3.通过对泥炭藓植物的排序,进一步阐明了泥炭藓属内的各个种之间的系统位置。本文首次将数量分类用于泥炭藓植物,通过研究,认为该方法用于其它苔藓植物也是可行的,这对苔藓植物定量地、准确地表现分类群的系统位置及亲缘关系,将有一定的参考价值。     

中国西藏藓类植物四新种

植物体中等大小,黄绿色或暗绿色,茎高5-8厘米,具3-5分枝下部和中上部被稀疏假根。叶密生,宽披针形,基部宽,向上渐狭,潮湿时伸展,干燥时稍呈镰刀状弯曲;叶缘平展,上部具齿突,中肋较宽,长达时尖部或突出,上部背面具齿突,横切面主细胞排列不整齐,其背、腹两侧均有分化付细胞;叶片中下部细胞长形,不规则,壁强烈加厚,具明显壁孔,上部细胞不整齐,略呈多边形,背面买明显的疵,角细胞发达,黄褐色,通常由3-4层细胞组成。     

东北蕨类植物配子体发育的研究Ⅱ.卷柏科

卷柏科仅一属,在东北共记载有10种。卷柏属为异型孢子蕨类,配子体在其大小孢子壁内萌发,但在自然条件下很难采到其配子体,室内培养也较困难,关于配子体的发育和受精的时间场所,至今不十分明确。Wetmore Morel等(1951)曾将卷柏属中的两个种即Selaginella pallescens(presl.)Spr.和S.flabellata Spr.的大孢子接种在培养基上,获得雌配子体,但文章中未涉及各发育阶段的细节,也没有附图和相片。Slagg(1932)做了卷柏属的一种、S.kraussiana(Kze.)A.Br.雄配子体发育的研究。Yuasa(1933)对S.involvense Spr.的精子形态有过报告,该种为本文研究的Selaginella tamariscina(Beauv.)Spr.的同物异名,但对其雌雄配子体和幼孢子体的发育工作未见有过报导。     

东北蕨类植物配子体发育的研究Ⅲ.紫萁科

紫萁科东北记载有2种,笔者采到的孢子仅紫萁属的亚洲分株紫萁(Osmunda cinnamomea L.var.asiatica Fernald),此为分株紫萁(O.cinnamomea L.)分布于亚洲的变种。Yuasa(1935)观察过分株紫萁的精子结构。Momose(1942)做过日本紫萁(O.japonica Thunb.)孢子萌发的研究。Hasegawa(1955)一般地报导了产于日本的紫萁属3个种的有性世代。Stokey(1956)对紫萁科3属中的7个种做过其配子体的培养研究,其中有分株紫萁(O.cinnamomea L.)。     

Gram-Positive Bacterial Lipoglycans Based on a Glycosylated Diacylglycerol Lipid Anchor Are Microbe-Associated Molecular Patterns Recognized by TLR2

Innate immune recognition is the first line of host defense against invading microorganisms. It is a based on the detection, by pattern recognition receptors (PRRs), of invariant molecular signatures that are unique to microorganisms. TLR2 is a PRR that plays a major role in the detection of Gram-positive bacteria by recognizing cell envelope lipid-linked polymers, also called macroamphiphiles, such as lipoproteins, lipoteichoic acids and mycobacterial lipoglycans. These microbe-associated molecular patterns (MAMPs) display a structure based on a lipid anchor, being either an acylated cysteine, a glycosylated diacylglycerol or a mannosyl-phosphatidylinositol respectively, and having in common a diacylglyceryl moiety. A fourth class of macroamphiphile, namely lipoglycans, whose lipid anchor is made, as for lipoteichoic acids, of a glycosylated diacylglycerol unit rather than a mannosyl-phosphatidylinositol, is found in Gram-positive bacteria and produced by certain Actinobacteria, including Micrococcus luteus, Stomatococcus mucilaginosus and Corynebacterium glutamicum. We report here that these alternative lipoglycans are also recognized by TLR2 and that they stimulate TLR2-dependant cytokine production, including IL-8, TNF-α and IL-6, and cell surface co-stimulatory molecule CD40 expression by a human macrophage cell line. However, they differ by their co-receptor requirement and the magnitude of the innate immune response they elicit. M. luteus and S. mucilaginosus lipoglycans require TLR1 for recognition by TLR2 and induce stronger responses than C. glutamicum lipoglycan, sensing of which by TLR2 is dependent on TLR6. These results expand the repertoire of MAMPs recognized by TLR2 to lipoglycans based on a glycosylated diacylglycerol lipid anchor and reinforce the paradigm that macroamphiphiles based on such an anchor, including lipoteichoic acids and alternative lipoglycans, induce TLR2-dependant innate immune responses.     

A non-canonical plant microRNA target site

Plant microRNAs (miRNAs) typically form near-perfect duplexes with their targets and mediate mRNA cleavage. Here, we describe an unconventional miRNA target of miR398 in Arabidopsis, an mRNA encoding the blue copper-binding protein (BCBP). BCBP mRNA carries an miR398 complementary site in its 5′-untranslated region (UTR) with a bulge of six nucleotides opposite to the 5′ region of the miRNA. Despite the disruption of a target site region thought to be especially critical for function, BCBP mRNAs are cleaved by ARGONAUTE1 between nucleotides 10th and 11th, opposite to the miRNA, like conventional plant target sites. Levels of BCBP mRNAs are inversely correlated to levels of miR398 in mutants lacking the miRNA, or transgenic plants overexpressing it. Introducing two mutations that disrupt the miRNA complementarity around the cleavage site renders the target cleavage-resistant. The BCBP site functions outside of the context of the BCBP mRNA and does not depend on 5′-UTR location. Reducing the bulge does not interfere with miR398-mediated regulation and completely removing it increases the efficiency of the slicing. Analysis of degradome data and target predictions revealed that the miR398-BCBP interaction seems to be rather unique. Nevertheless, our results imply that functional target sites with non-perfect pairings in the 5′ region of an ancient conserved miRNA exist in plants.