All in the family

The Evolution of Sibling Rivalry by D.W. Mock and G.A. Parker Oxford University Press, 1998. $120.00 hbk, $55.00 pbk (xiii +464 pages) ISBN 0 19 857743 5/0 19 857744 3.     

All in the family: the UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases

Mucin-type linkages (GalNAcalpha1-O-Ser/Thr) are initiated by a family of glycosyltransferases known as the UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltransferases (ppGaNTases, EC 2.4.1.41). These enzymes transfer GalNAc from the sugar donor UDP-GalNAc to serine and threonine residues, forming an alpha anomeric linkage. Despite the seeming simplicity of ppGaNTase catalytic function, it is estimated on the basis of in silico analysis that there are 24 unique ppGaNTase human genes. ppGaNTase isoforms display tissue-specific expression in adult mammals as well as unique spatial and temporal patterns of expression during murine development. In vitro assays suggest that a subset of the ppGaNTases have overlapping substrate specificities, but at least two ppGaNTases (ppGaNTase-T7 and -T9 [now designated -T10]) appear to require the prior addition of GalNAc to a synthetic peptide before they can catalyze sugar transfer to this substrate. Site-specific O-glycosylation by several ppGaNTases is influenced by the position and structure of previously added O-glycans. Collectively, these observations argue in favor of a hierarchical addition of core GalNAc residues to the apomucin. Various forms of O-glycan pathobiology may be reexamined in light of the existence of an extensive ppGaNTase family of enzymes. Recent work has demonstrated that at least one ppGaNTase isoform is required for normal development in Drosophila melanogaster. Structural insights will no doubt lead to the development of isoform-specific inhibitors. Such tools will prove valuable to furthering our understanding of the functional roles played by O-glycans.     

All in the family: evolutionary and functional relationships among death receptors

Over the last decade, significant progress has been made towards identifying the signaling pathways within mammalian cells that lead to apoptosis mediated by death receptors. The simultaneous expression of more than one death receptor in many, if not all, cell types suggests that functional innovation has driven the divergence of these receptors and their cognate ligands. To better understand the physiological divergence of the death receptors, a phylogenetic analysis of vertebrate death receptors was conducted based upon amino-acid sequences encoding the death domain regions of currently known and newly identified members of the family. Evidence is presented to indicate an ancient radiation of death receptors that predates the emergence of vertebrates, as well as ongoing divergence of additional receptors both within several receptor lineages as well as modern taxonomic lineages. We speculate that divergence among death receptors has led to their functional specialization. For instance, some receptors appear to be primarily involved in mediating the immune response, while others play critical roles during development and tissue differentiation. The following represents an evolutionary approach towards an understanding of the complex relationship among death receptors and their proposed physiological functions in vertebrate species.     

The Vein Patterning 1 (VEP1) gene family laterally spread through an ecological network

Lateral gene transfer (LGT) is a major evolutionary mechanism in prokaryotes. Knowledge about LGT--particularly, multicellular--eukaryotes has only recently started to accumulate. A widespread assumption sees the gene as the unit of LGT, largely because little is yet known about how LGT chances are affected by structural/functional features at the subgenic level. Here we trace the evolutionary trajectory of VEin Patterning 1, a novel gene family known to be essential for plant development and defense. At the subgenic level VEP1 encodes a dinucleotide-binding Rossmann-fold domain, in common with members of the short-chain dehydrogenase/reductase (SDR) protein family. We found: i) VEP1 likely originated in an aerobic, mesophilic and chemoorganotrophic α-proteobacterium, and was laterally propagated through nets of ecological interactions, including multiple LGTs between phylogenetically distant green plant/fungi-associated bacteria, and five independent LGTs to eukaryotes. Of these latest five transfers, three are ancient LGTs, implicating an ancestral fungus, the last common ancestor of land plants and an ancestral trebouxiophyte green alga, and two are recent LGTs to modern embryophytes. ii) VEP1's rampant LGT behavior was enabled by the robustness and broad utility of the dinucleotide-binding Rossmann-fold, which provided a platform for the evolution of two unprecedented departures from the canonical SDR catalytic triad. iii) The fate of VEP1 in eukaryotes has been different in different lineages, being ubiquitous and highly conserved in land plants, whereas fungi underwent multiple losses. And iv) VEP1-harboring bacteria include non-phytopathogenic and phytopathogenic symbionts which are non-randomly distributed with respect to the type of harbored VEP1 gene. Our findings suggest that VEP1 may have been instrumental for the evolutionary transition of green plants to land, and point to a LGT-mediated 'Trojan Horse' mechanism for the evolution of bacterial pathogenesis against plants. VEP1 may serve as tool for revealing microbial interactions in plant/fungi-associated environments.     

Reports in Pteridaceae (Filacales) family in the Neotropics

Several contributions to the Neotropical pteridophyte flora are made in this paper with the range extensions for four species of Adiantum, two species of Doryopteris and one species of Eriosorus. The species concerned are: A. polyphyllum Willd. for Nicaragua and Costa Rica; A. trichochlaenum Mickel et Beitel for Guatemala and Costa Rica; A. villosissimum Mett. ex Kuhn for Costa Rica; A. wilesianum Hook. for Nicaragua; D. nobilis (T. Moore) C. Chr. for Costa Rica, Colombia and Venezuela; D. redivida Fée for Panama; and E. hirtus (Kunth) Copel. for Costa Rica. The concept of D. pedata (L.) Fée is redefined.     

Endogenous lentiviral elements in the weasel family (mustelidae)

Endogenous retroviruses provide molecular fossils for studying the ancient evolutionary history of retroviruses. Here, we report our independent discovery and analysis of endogenous lentiviral insertions (Mustelidae endogenous lentivirus [MELV]) within the genomes of weasel family (Mustelidae). Genome-scale screening identified MELV elements in the domestic ferret (Mustela putorius furo) genome (MELVmpf). MELVmpf exhibits a typical lentiviral genomic organization. Phylogenetic analyses position MELVmpf basal to either primate lentiviruses or feline immunodeficiency virus. Moreover, we verified the presence of MELV insertions in the genomes of several species of the Lutrinae and Mustelinae subfamilies but not the Martinae subfamily, suggesting that the invasion of MELV into the Mustelidae genomes likely took place between 8.8 and 11.8 Ma. The discovery of MELV in weasel genomes extends the host range of lentiviruses to the Caniformia (order Carnivora) and provides important insights into the prehistoric diversity of lentiviruses.     

Subfamily separation in the hemipteran family Gelastocoridae (Hemiptera)

Gelastocoridae (Kirkaldy, 1897) has over 70 species in two subfamilies: Nerthrinae (Kirkaldy, 1898), genus Nerthra (Say, 1832) and Gelastocorinae (Champion, 1901), genus Gelastocoris (Kirkaldy, 1897). The position of the cephalic gland openings, presence and shape of the gular bridge and the number and position of abdominal spiracles, are presented as new morphologic diagnostic characteristics that support the argument used by Todd for the segregation of the subfamilies. The characteristics are described and illustrated on the basis of specimens from Laguna Iberá, Corrientes, Argentina.     

柔膜菌科并非单系群

对柔膜菌科部分属的18S rDNA、28S rDNA和MCM7基因进行序列分析,初步探讨了该科属间的系统发育关系。结果表明,同属的不同种表现出较高序列相似性,聚类在一起,分别形成独立的分支,从而说明这些属的概念比较清晰。但是,柔膜菌科的参试属并没有聚类在一起,其中部分属似乎与其他科的关系更近,表明该科并非单系群。     

Evolutionary relationships in the showy mistletoe family (Loranthaceae)

Loranthaceae (73 genera and ca. 900 species) comprise mostly aerial hemiparasitic plants. Three monotypic genera considered relicts are root parasites. The family is diverse in tropical areas, but representatives are also found in temperate habitats. Previous classifications were based on floral and inflorescence morphology, karyological information, and biogeography. The family has been divided into three tribes: Nuytsiae, Elytrantheae (subtribes Elytranthinae and Gaiadendrinae), and Lorantheae (subtribes Loranthinae and Psittacanthinae). Nuytsiae and Elytrantheae are characterized by a base chromosome number of x = 12, whereas subtribes Loranthinae (x = 9) and Psittacanthinae (x = 8) numbers are derived via aneuploid reduction. To elucidate the phylogeny of the family, we analyzed sequences from five genes (nuclear small and large subunit rDNA and the chloroplast genes rbcL, matK, and trnL-F) representing most genera using parsimony, likelihood, and Bayesian inference. The three root parasites, Nuytsia, Atkinsonia, and Gaiadendron, are supported as successive sister taxa to the remaining genera, resulting in a monophyletic group of aerial parasites. Three major clades are resolved each corresponding to a subtribe. However, two South American genera (Tristerix and Notanthera) and the New Zealand genus Tupeia, which were previously classified in subtribe Elytranthinae, are weakly supported as part of a clade representing the South American subtribe Psittacanthinae.     

Checklist of the family Culicidae (Diptera) in Finland

A checklist of the Culicidae (Diptera) recorded from Finland is provided.