The four hexamerin genes in the honey bee: structure,molecular evolution and function deduced from expression patterns in queens,workers and drones

Background  

Hexamerins are hemocyanin-derived proteins that have lost the ability to bind copper ions and transport oxygen; instead, they became storage proteins. The current study aimed to broaden our knowledge on the hexamerin genes found in the honey bee genome by exploring their structural characteristics, expression profiles, evolution, and functions in the life cycle of workers, drones and queens.     

叶绿素b聚集体和它的能化态的性质

叶绿素b由单体聚合成多聚体后吸收光谱明显红移。叶绿素b聚集体膜在光下产生150 mV的光电位,停止照光后此电位消失速度比叶绿素a聚集体膜的慢。叶绿素b聚集体吸收光能后形成相当稳定的能化态,半生命期约几分钟。当聚集体解聚时所吸收的光能又以光的形式辐射出来。叶绿素b聚集体能化态的能量可快速而有效地传给叶绿素a聚集体,以叶绿素a的延迟发光形式释放出来。     

Pig Reticulocytes. III. Glucose permeability in naturally occurring reticulocytes and red cells from newborn piglets

The loss of facilitated glucose transport of red cells occurring in the newborn pig was monitored in 11 density-separated cells from birth to a 4 wk of age. At birth there was a threefold increase in glucose permeability from the lightest cells to the most dense, suggesting that cells having progressively less glucose permeability are released into the circulation as gestation proceeds. Because of extraordinary stimulation of erythropoietic activity, the uppermost top fraction constituting 2-3 percent of the total cells is composed purely of reticulocytes in the growing animal. The glucose permeability of these reticulocytes which at birth has a slow but significant rate of 3.7 μmol/ml cell x min at 25 degrees C is rapidly decreased within 3-4 days to the level of reticulocytes produced in the adult in response to phenylhydrazine assault. Moreover, reticulocytes themselves discard their membrane permeability to glucose in the course of maturation to red cells. Thus, even though reticulocytes at birth are permeable to glucose, they will become red cells practically impervious to glucose within a few days. These findings suggest that the transition from a glucose- permeable fetal state to a glucose-impermeable postnatal state is brought about by two mechanisms: (a) dilution of fetal cells by glucose-impervious cells produced coincidentally with or shortly after birth; and (b) elimination of fetal cells, which have a shorter half-life, from the circulation.     

Molecular evolution of P transposable elements in the genus Drosophila. I. The saltans and willistoni species groups

A phylogenetic survey using the polymerase chain reaction (PCR) has identified four major P element subfamilies in the saltans and willistoni species groups of Drosophila. One subfamily, containing about half of the sequences studied, consists of elements that are very similar to the canonical (and active) P element from D. melanogaster. Within this subfamily, nucleotide sequence differentiation among different copies from the same species and among elements from different species is relatively low. This observation suggests that the canonical elements are relatively recent additions to the genome or, less likely, are evolving slowly relative to the other subfamilies. Elements belonging to the three noncanonical lineages are distinct from the canonical elements and from one another. Furthermore, there is considerably more sequence variation, on the average, within the noncanonical subfamilies compared to the canonical elements. Horizontal transfer and the coexistence of multiple, independently evolving element subfamilies in the same genome may explain the distribution of P elements in the saltans and willistoni species groups. Such explanations are not mutually exclusive, and each may be involved to varying degrees in the maintenance of P elements in natural populations of Drosophila.      

Evaluation of apoptosis markers in different cell lines infected with equine arteritis virus

Equine arteritis virus (EAV) induces apoptosis in infected cells. Cell death caused by EAV has been studied mainly using three cell lines, BHK-21, RK-13 and Vero cells. The mechanism of apoptosis varies among cell lines and results cannot be correlated owing to differences in EAV strains used. We evaluated different markers for apoptosis in BHK-21, RK-13 and Vero cell lines using the Bucyrus EAV reference strain. Acridine orange/ethidium bromide staining revealed morphological changes in infected cells, while flow cytometry indicated the extent of apoptosis. We also observed DNA fragmentation, but the DNA ladder was detected at different times post-infection depending on the cell line, i.e., 48, 72 and 96 h post-infection in RK-13, Vero and BHK-21 cells, respectively. Measurement of viral titers obtained with each cell line indicated that apoptosis causes interference with viral replication and therefore decreased viral titers. As an unequivocal marker of apoptosis, we measured the expression of caspase-3 and caspases-8 and -9 as extrinsic and intrinsic markers of apoptosis pathways, respectively. Caspase-8 in BHK-21 cells was the only protease that was not detected at any of the times assayed. We found that Bucyrus EAV strain exhibited a distinctive apoptosis pathway depending on the cell line.     

Human MutL-complexes monitor homologous recombination independently of mismatch repair

The role of mismatch repair proteins has been well studied in the context of DNA repair following DNA polymerase errors. Particularly in yeast, MSH2 and MSH6 have also been implicated in the regulation of genetic recombination, whereas MutL homologs appeared to be less important. So far, little is known about the role of the human MutL homolog hMLH1 in recombination, but recently described molecular interactions suggest an involvement. To identify activities of hMLH1 in this process, we applied an EGFP-based assay for the analysis of different mechanisms of DNA repair, initiated by a targeted double-stranded DNA break. We analysed 12 human cellular systems, differing in the hMLH1 and concomitantly in the hPMS1 and hPMS2 status via inducible protein expression, genetic reconstitution, or RNA interference. We demonstrate that hMLH1 and its complex partners hPMS1 and hPMS2 downregulate conservative homologous recombination (HR), particularly when involving DNA sequences with only short stretches of uninterrupted homology. Unexpectedly, hMSH2 is dispensable for this effect. Moreover, the damage-signaling kinase ATM and its substrates BLM and BACH1 are not strictly required, but the combined effect of ATM/ATR-signaling components may mediate the anti-recombinogenic effect. Our data indicate a protective role of hMutL-complexes in a process which may lead to detrimental genome rearrangements, in a manner which does not depend on mismatch repair.     

Phylogenetic relationships among prokaryotic and eukaryotic catalases

Seventy-four catalase protein sequences, including 29 bacterial, 8 fungal, 7 animal, and 30 plant sequences, were compiled, and 70 were used for phylogenetic reconstruction. The core of the resulting tree revealed unique, separate groups of plant and animal catalases, two groups of fungal catalases, and three groups of bacterial catalases. The only overlap of kingdoms occurred within one branch and involved fungal and bacterial large-subunit enzymes. The other fungal branch was closely linked to the group of animal enzymes. Group I bacterial catalases were more closely related to the plant enzymes and contained such diverse taxa as the Gram-positive Listeria seeligeri, Deinocococcus radiodurans, and gamma-proteobacteria. Group III bacterial sequences were more closely related to fungal and animal sequences and included enzymes from a broad range of bacteria including high- and low-GC Gram positives, proteobacteria, and a bacteroides species. Group II was composed of large-subunit catalases from diverse sources including Gram positives (low-GC Bacilli and high-GC Mycobacteria), proteobacteria, and species of the filamentous fungus Aspergillus. These data can be interpreted in terms of two gene duplication events that produced a minimum of three catalase gene family members that subsequently evolved in response to environmental demands. Horizontal gene transfer may have been responsible for the group II mixture of bacterial and fungal large-subunit catalases.      

Sequence variation in the guillemot (Alcidae: Cepphus) mitochondrial control region and its nuclear homolog

We describe sequence variation in the mitochondrial control region and its nuclear homolog in three species and seven subspecies of guillemots (Cepphus spp.). Nuclear homologs of the 5' end of the control region were found in all individuals. Nuclear sequences were approximately 50% divergent from their mitochondrial counterparts and formed a distinct phylogenetic clade; the mitochondrial-nuclear introgression event must have predated the radiation of Cepphus. As in other vertebrates, the guillemot control region has a relatively conserved central block flanked by hypervariable 5' and 3' ends. Mean pairwise interspecific divergence values among control regions were lower than those in other birds. All individuals were heteroplasmic for the number of simple tandem nucleotide repeats (A(n)C) at the 3' end of the control region. Phylogenetic analyses suggest that black guillemots are basal to pigeon and spectacled guillemots, but evolutionary relationships among subspecies remain unresolved, possibly due to incomplete lineage sorting. Describing molecular variation in nuclear homologs of mitochondrial genes is of general interest in phylogenetics because, if undetected, the homologs may confound interpretations of mitochondrial phylogenies.