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1.
Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae) 总被引:5,自引:0,他引:5
Campbell CS; Wojciechowski MF; Baldwin BG; Alice LA; Donoghue MJ 《Molecular biology and evolution》1997,14(1):81-90
Individual plants of several Amelanchier taxa contain many polymorphic
nucleotide sites in the internal transcribed spacers (ITS) of nuclear
ribosomal DNA (nrDNA). This polymorphism is unusual because it is not
recent in origin and thus has resisted homogenization by concerted
evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the
result of gene flow between two major North American clades resolved by
phylogenetic analysis of ITS sequences. Western North American species plus
A. humilis and A. sanguinea of eastern North America form one clade (A),
and the remaining eastern North American Amelanchier make up clade B. Five
eastern North American taxa are polymorphic at many of the nucleotide sites
where clades A and B have diverged and are thought to be of hybrid origin,
with A. humilis or A. sanguinea as one parent and various members of clade
B as the other parent. Morphological evidence suggests that A. humilis is
one of the parents of one of the polymorphic taxa, a microspecies that we
refer to informally as A. "erecta." Sequences of 21 cloned copies of the
ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical
to A. humilis sequence or to the clade B consensus sequence, or they are
apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier
"erecta" and another polymorphic taxon are suspected to be relatively old
because both grow several hundred kilometers beyond the range of one of
their parents. ITS sequence polymorphisms have apparently persisted in
these two taxa perhaps because of polyploidy and/or agamospermy (asexual
seed production), which are prevalent in the genus.
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2.
Schistosomiasis vector snails are subjected to extreme seasonal changes, particularly in ephemeral rivers and lentic waterbodies. In the tropics, aestivation is one of the adaptive strategies for survival and is used by snails in times of extremely high temperatures and desiccation. Aestivation therefore plays an important role in maintaining the transmission of schistosomiasis. This review assesses the possible impacts of climate change on the temporal and spatial distribution of schistosomiasis-transmitting snails with special emphasis on aestivation, and discusses the effect of schistosome infection on aestivation ability. The impacts of parasite development on snails, as well as physiological changes, are discussed with reference to schistosomiasis transmission. This review shows that schistosome-infected snails have lower survival rates during aestivation, and that those that survive manage to get rid of the infection. In general, snail aestivation ability is poor and survival chances diminish with time. Longer dry periods result in fewer, as well as uninfected, snails. However, the ability of the surviving snails to repopulate the habitats is high. 相似文献
3.
4.
Most cells enter mitosis once they have reached a defined size. In the fission yeast Schizosaccharomyces pombe, mitotic entry is orchestrated by a geometry-sensing mechanism that involves the Cdk1/Cdc2-inhibiting Wee1 kinase. The factors upstream of Wee1 gather together in interphase to form a characteristic medial and cortical belt of nodes. Nodes are also considered to be precursors of the cytokinesis contractile actomyosin ring (CAR). Here we describe a new component of the interphase nodes and cytokinesis rings, which we named Nod1. Consistent with its role in cell size control at division, nod1Δ cells were elongated and epistatic with regulators of Wee1. Through biochemical and localisation studies, we placed Nod1 in a complex with the Rho-guanine nucleotide exchange factor Gef2. Nod1 and Gef2 mutually recruited each other in nodes and Nod1 also assembles Gef2 in rings. Like gef2Δ, nod1Δ cells showed a mild displacement of their division plane and this phenotype was severely exacerbated when the parallel Polo kinase pathway was also compromised. We conclude that Nod1 specifies the division site by localising Gef2 to the mitotic cell middle. Previous work showed that Gef2 in turn anchors factors that control the spatio-temporal recruitment of the actin nucleation machinery. It is believed that the actin filaments originated from the nodes pull nodes together into a single contractile ring. Surprisingly however, we found that node proteins could form pre-ring helical filaments in a cdc12-112 mutant in which nucleation of the actin ring is impaired. Furthermore, the deletion of either nod1 or gef2 created an un-expected situation where different ring components were recruited sequentially rather than simultaneously. At later stages of cytokinesis, these various rings appeared inter-fitted rather than merged. This study brings a new slant to the understanding of CAR assembly and function. 相似文献
5.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
6.
Jason A Roberts Michael S Roberts Andrew Semark Andrew A Udy Carl MJ Kirkpatrick David L Paterson Matthew J Roberts Peter Kruger Jeffrey Lipman 《BMC anesthesiology》2011,11(1):1-7
Background
Critical illness, mediated by trauma or sepsis, can lead to physiological changes that alter the pharmacokinetics of antibiotics and may result in sub-therapeutic concentrations at the sites of infection. The first aim of this project is to identify the clinical characteristics of critically ill patients with significant trauma that have been recently admitted to ICU that may predict the dosing requirements for the antibiotic, cefazolin. The second aim of this is to identify the clinical characteristics of critically ill patients with sepsis that may predict the dosing requirements for the combination antibiotic, piperacillin-tazobactam.Methods/Design
This is an observational pharmacokinetic study of patients with trauma (cefazolin) or with sepsis (piperacillin-tazobactam). Participants will have samples from blood and urine, collected at different intervals. Patients will also have a microdialysis catheter inserted into subcutaneous tissue to measure interstitial fluid penetration of the antibiotic. Participants will be administered sinistrin, indocyanine green and sodium bromide as well as have cardiac output monitoring performed and tetrapolar bioimpedance to determine physiological changes resulting from pathology. Analysis of samples will be performed using validated liquid chromatography tandem mass-spectrometry. Pharmacokinetic analysis will be performed using non-linear mixed effects modeling to determine individual and population pharmacokinetic parameters of antibiotics.Discussion
The study will describe cefazolin and piperacillin-tazobactam concentrations in plasma and the interstitial fluid of tissues in trauma and sepsis patients respectively. The results of this study will guide clinicians to effectively dose these antibiotics in order to maximize the concentration of antibiotics in the interstitial fluid of tissues. 相似文献7.
Ram Krishna Thakur Vinod Kumar Yadav Akinchan Kumar Ankita Singh Krishnendu Pal Luke Hoeppner Dhurjhoti Saha Gunjan Purohit Richa Basundra Anirban Kar Rashi Halder Pankaj Kumar Aradhita Baral MJ Mahesh Kumar Alfonso Baldi Bruno Vincenzi Laura Lorenzon Rajkumar Banerjee Praveen Kumar Viji Shridhar Debabrata Mukhopadhyay Shantanu Chowdhury 《Nucleic acids research》2014,42(18):11589-11600
8.
Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase 下载免费PDF全文
Sharon C Mithoe Christina Ludwig Michiel JC Pel Mara Cucinotta Alberto Casartelli Malick Mbengue Jan Sklenar Paul Derbyshire Silke Robatzek Corné MJ Pieterse Ruedi Aebersold Frank LH Menke 《EMBO reports》2016,17(3):441-454
Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLIN‐SENSITIVE 2 (FLS2) induces the activation of mitogen‐activated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellin‐triggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7‐mediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex. 相似文献
9.
10.
Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction. 相似文献