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51.
Use of arboreal and terrestrial space by a small mammal community in a tropical rain forest in Borneo, Malaysia 总被引:4,自引:0,他引:4
Konstans Wells Martin Pfeiffer Maklarin B. Lakim K. Eduard Linsenmair 《Journal of Biogeography》2004,31(4):641-652
Aim Small mammals were live‐trapped in a primary rain forest to evaluate the relative distribution of species to each other and to microhabitat properties on the ground and in the canopy. Location Kinabalu National Park in Borneo, Sabah, Malaysia. Methods Seven trapping sessions were conducted along two grids with 31 trap points at distances of 20 m on the ground and in the lower canopy at an average height of 13.5 m. Results Species diversity and abundance of small mammals proved to be high: 20 species of the families Muridae, Sciuridae, Tupaiidae, Hystricidae, Viverridae and Lorisidae were trapped, with murids being dominant in both habitat layers. The terrestrial community was significantly more diverse with 16 captured species (Shannon–Wiener's diversity index = 2.47), while 11 species were trapped in the canopy ( = 1.59). The Whitehead's rat, Maxomys whiteheadi, and the red spiny rat, Maxomys surifer, dominated the terrestrial community whereas the large pencil‐tailed tree mouse, Chiropodomys major, was by far the most abundant species in the canopy. Other abundant species of the canopy community, the dark‐tailed tree rat, Niviventer cremoriventer, and the lesser treeshrew, Tupaia minor, were also abundant on the ground, and there was no clear boundary between arboreal and terrestrial species occurrences. Main conclusions As most species were not confined to specific microhabitats or habitat layers, species seemed to rely on resources not necessarily restricted to certain microhabitats or habitat layers, and separation of species probably resulted mainly from a species’ concentrated activity in a preferred microhabitat rather than from principal adaptations to certain habitats. Ecological segregation was stronger in the more diverse terrestrial community, though microhabitat selection was generally not sufficient to explain the co‐occurrences of species and the variability between local species assemblages. Constraints on small mammal foraging efficiency in the three‐dimensional more complex canopy may be responsible for the similarity of microhabitat use of all common arboreal species. Community composition was characterized by mobile species with low persistence rates, resulting in a high degree of variability in local species assemblages with similar turnover rates in both habitats. 相似文献
52.
Bringaud F Biteau N Zuiderwijk E Berriman M El-Sayed NM Ghedin E Melville SE Hall N Baltz T 《Molecular biology and evolution》2004,21(3):520-528
The ingi (long and autonomous) and RIME (short and nonautonomous) non--long-terminal repeat retrotransposons are the most abundant mobile elements characterized to date in the genome of the African trypanosome Trypanosoma brucei. These retrotransposons were thought to be randomly distributed, but a detailed and comprehensive analysis of their genomic distribution had not been performed until now. To address this question, we analyzed the ingi/RIME sequences and flanking sequences from the ongoing T. brucei genome sequencing project (TREU927/4 strain). Among the 81 ingi/RIME elements analyzed, 60% are complete, and 7% of the ingi elements (approximately 15 copies per haploid genome) appear to encode for their own transposition. The size of the direct repeat flanking the ingi/RIME retrotransposons is conserved (i.e., 12-bp), and a strong 11-bp consensus pattern precedes the 5'-direct repeat. The presence of a consensus pattern upstream of the retroelements was confirmed by the analysis of the base occurrence in 294 GSS containing 5'-adjacent ingi/RIME sequences. The conserved sequence is present upstream of ingis and RIMEs, suggesting that ingi-encoded enzymatic activities are used for retrotransposition of RIMEs, which are short nonautonomous retroelements. In conclusion, the ingi and RIME retroelements are not randomly distributed in the genome of T. brucei and are preceded by a conserved sequence, which may be the recognition site of the ingi-encoded endonuclease. 相似文献
53.
Bobrowicz P Davidson RC Li H Potgieter TI Nett JH Hamilton SR Stadheim TA Miele RG Bobrowicz B Mitchell T Rausch S Renfer E Wildt S 《Glycobiology》2004,14(9):757-766
A significant percentage of eukaryotic proteins contain posttranslationalmodifications, including glycosylation, which are required forbiological function. However, the understanding of the structurefunctionrelationships of N-glycans has lagged significantly due to themicroheterogeneity of glycosylation in mammalian produced proteins.Recently we reported on the cellular engineering of yeast toreplicate human N-glycosylation for the production of glycoproteins.Here we report the engineering of an artificial glycosylationpathway in Pichia pastoris blocked in dolichol oligosaccharideassembly. The PpALG3 gene encoding Dol-P-Man:Man5GlcNAc2-PP-Dolmannosyltransferase was deleted in a strain that was previouslyengineered to produce hybrid GlcNAcMan5GlcNAc2 human N-glycans.Employing this approach, combined with the use of combinatorialgenetic libraries, we engineered P. pastoris strains that synthesizecomplex GlcNAc2Man3GlcNAc2 N-glycans with striking homogeneity.Furthermore, through expression of a Golgi-localized fusionprotein comprising UDP-glucose 4-epimerase and ß-1,4-galactosyltransferase activities we demonstrate that this structure isa substrate for highly efficient in vivo galactose addition.Taken together, these data demonstrate that the artificial invivo glycoengineering of yeast represents a major advance inthe production of glycoproteins and will emerge as a practicaltool to systematically elucidate the structurefunctionrelationship of N-glycans.
1 These authors contributed equally to this work. 2 To whom correspondence should be addressed; e-mail: swildt{at}glycofi.com 相似文献
54.
Major glycolipids [monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG)) and phospholipids (phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG)] as well as betaine lipid 1,2-diacylglycero-O-4'-(N,N,N-tri-methyl)-homoserine (DGTS) were isolated from Anfeltia tobuchiensis (Rhodophyta), Laminaria japonica, Sargassum pallidum (Phaeophyta), Ulva fenestrata (Chlorophyta) and Zostera marina (Embriophyta), harvested in the Sea of Japan. GC analysis of their fatty acid (FA) composition revealed that the n-6 polyunsaturated FAs (PUFAs) shared the most part of the sum of n-6 and n-3 PUFAs in PC and PE compared with glycolipids and PG. In algae, it was related to the prevalence of 20:4n-6 over 20:5n-3 in non-photosynthetic lipids. Percentage of n-6 PUFAs as well as the sum of n-3 and n-6 PUFAs decreased in the following sequence: PC-->PE-->PG. The saturation increased in the lines of MGDG-->DGDG-->SQDG and PC-->PE-->PG. PG was close to SQDG by the level of saturation. Distribution of C(18) and C(20) PUFAs in polar lipids depended on taxonomic position of macrophytes. Balance between C(18) and C(20) PUFAs was preferably shifted to the side of C(20) PUFAs in PC and PE that was observed in contrast to glycolipids and PG from L. japonica containing both series of FAs. The set of major FAs of polar lipid classes can essentially differ from each other and from total lipids of macrophytes. For example, MGDG was found to accumulate characteristic fatty acids 16:4n-3, 16:3n-3, 18:3n-6 and 18:4n-3, 20:3n-6 in U. fenestrata, Z. marina, L. japonica and S. pallidum, respectively. 相似文献
55.
Microtubules of guard cells are light sensitive 总被引:7,自引:0,他引:7
Guard cells of stomata are characterized by ordered bundles of microtubules radiating from the ventral side toward the dorsal side of the cylindrical cell. It was suggested that microtubules play a role in directing the radial arrangement of the cellulose micro-fibrils of guard cells. However, the role of microtubules in daily cycles of opening and closing of stomata is not clear. The organization of microtubules in guard cells of Commelina communis leaves was studied by analysis of three-dimensional immunofluorescent images. It was found that while guard cell microtubules in the epidermis of leaves incubated in the light were organized in parallel, straight and dense bundles, in the dark they were less straight and oriented randomly near the stomatal pore. The effect of blue and red light on the organization of guard cell microtubules resembled the effects of white light and dark respectively. When stomata were induced to open in the dark with fusicoccin, microtubules remained in the dark configuration. Furthermore, when incubated in the light, guard cell microtubules were more resistant to oryzalin. Similarly, microtubules of Arabidopsis guard cells, expressing green fluorescent protein-tubulin alpha 6, were disorganized in the dark, but were organized in parallel arrays in the presence of white light. The dynamics of microtubule rearrangement upon transfer of intact leaves from dark to light was followed in single stomata, showing that an arrangement of microtubules typical for light conditions was obtained after 1 h in the light. Our data suggest that microtubule organization in guard cells is responsive to light signals. 相似文献
56.
The majority of army ant species forage hypogaeically. Due to the difficulties in observing these ants, their potential influence on hypogaeic and epigaeic arthropod communities has not yet been investigated. As the first hypogaeically foraging army ant studied in detail, we attracted Dorylus laevigatus to areas monitored for their arthropod diversity. Here, for the first time, the same sites were sampled before and after an army ant raid. Furthermore, interactions between D. laevigatus and the five most common ground-nesting ant species were noted and their life-history traits compared, allowing first inferences on possible mechanisms of their coexistence. The occurrence of D. laevigatus within a study plot had no evident effect on the number of arthropod taxa or individuals collected with epigaeic and hypogaeic pitfall traps. Likewise, juvenile arthropods, which are less mobile and thus are potentially easier prey for D. laevigatus, showed no differences in their collected numbers before and after the army ant had visited a plot. However, significantly fewer ant species were collected with hypogaeic traps after D. laevigatus had been within the study plots, indicating a possible predation of D. laevigatus especially on two Pseudolasius and one Pheidole species. The five most common ground-foraging ant species demonstrated their ability to avoid, kill, and even prey on the army ant. The reaction of Lophomyrmex bedoti towards D. laevigatus indicated the former to be a potential prey species, while Pachycondyla sp. 2 showed signs of "enemy specification." Odontoponera diversus and O. transversa actively preyed on D. laevigatus, while Pheidologeton affinis fought with D. laevigatus over resources. All ant species could co-occur with D. laevigatus at palm oil baits. Adding to the differences detected in previous studies between D. laevigatus and epigaeically foraging army ant species, the occurrence of this hypogaeic army ant seems to have less devastating effects on arthropod community compositions than those of epigaeically mass raiding species. 相似文献
57.
Reciprocal and nonreciprocal recombination at the glucocerebrosidase gene region: implications for complexity in Gaucher disease
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Tayebi N Stubblefield BK Park JK Orvisky E Walker JM LaMarca ME Sidransky E 《American journal of human genetics》2003,72(3):519-534
Gaucher disease results from an autosomal recessive deficiency of the lysosomal enzyme glucocerebrosidase. The glucocerebrosidase gene is located in a gene-rich region of 1q21 that contains six genes and two pseudogenes within 75 kb. The presence of contiguous, highly homologous pseudogenes for both glucocerebrosidase and metaxin at the locus increases the likelihood of DNA rearrangements in this region. These recombinations can complicate genotyping in patients with Gaucher disease and contribute to the difficulty in interpreting genotype-phenotype correlations in this disorder. In the present study, DNA samples from 240 patients with Gaucher disease were examined using several complementary approaches to identify and characterize recombinant alleles, including direct sequencing, long-template polymerase chain reaction, polymorphic microsatellite repeats, and Southern blots. Among the 480 alleles studied, 59 recombinant alleles were identified, including 34 gene conversions, 18 fusions, and 7 downstream duplications. Twenty-two percent of the patients evaluated had at least one recombinant allele. Twenty-six recombinant alleles were found among 310 alleles from patients with type 1 disease, 18 among 74 alleles from patients with type 2 disease, and 15 among 96 alleles from patients with type 3 disease. Several patients carried two recombinations or mutations on the same allele. Generally, alleles resulting from nonreciprocal recombination (gene conversion) could be distinguished from those arising by reciprocal recombination (crossover and exchange), and the length of the converted sequence was determined. Homozygosity for a recombinant allele was associated with early lethality. Ten different sites of crossover and a shared pentamer motif sequence (CACCA) that could be a hotspot for recombination were identified. These findings contribute to a better understanding of genotype-phenotype relationships in Gaucher disease and may provide insights into the mechanisms of DNA rearrangement in other disorders. 相似文献
58.
Marco S Saura J Pérez-Navarro E José Martí M Tolosa E Alberch J 《Journal of neurobiology》2002,52(4):343-351
Glial cell line-derived neurotrophic factor (GDNF) family members have been proposed as candidates for the treatment of Parkinson's disease because they protect nigral dopaminergic neurons against various types of insult. However, the efficiency of these factors depends on the availability of their receptors after damage. We evaluated the changes in the expression of c-Ret, GFRalpha1, and GFRalpha2 in the substantia nigra pars compacta in a rat model of Parkinson's disease by in situ hybridization. Intrastriatal injection of 6-hydroxydopamine (6-OHDA) transiently increased c-Ret and GFRalpha1 mRNA levels in the substantia nigra pars compacta at 1 day postlesion. At later time points, 3 and 6 days, the expression of c-Ret and GFRalpha1 was downregulated. GFRalpha2 expression was differentially regulated, as it decreased only 6 days after 6-OHDA injection. Triple-labeling studies, using in situ hybridization for the GDNF family receptors and immunohistochemistry for neuronal or glial cell markers, showed that changes in the expression of c-Ret, GFRalpha1, and GFRalpha2 in the substantia nigra pars compacta were localized to neurons. In conclusion, our results show that nigral neurons differentially regulate the expression of GDNF family receptors as a transient and compensatory response to 6-OHDA lesion. 相似文献
59.
Ribonucleotide reductases (RNRs) are uniquely responsible for converting nucleotides to deoxynucleotides in all dividing
cells. The three known classes of RNRs operate through a free radical mechanism but differ in the way in which the protein
radical is generated. Class I enzymes depend on oxygen for radical generation, class II uses adenosylcobalamin, and the anaerobic
class III requires S-adenosylmethionine and an iron–sulfur cluster. Despite their metabolic prominence, the evolutionary origin and relationships
between these enzymes remain elusive. This gap in RNR knowledge can, to a major extent, be attributed to the fact that different
RNR classes exhibit greatly diverged polypeptide chains, rendering homology assessments inconclusive. Evolutionary studies
of RNRs conducted until now have focused on comparison of the amino acid sequence of the proteins, without considering how
they fold into space. The present study is an attempt to understand the evolutionary history of RNRs taking into account their
three-dimensional structure. We first infer the structural alignment by superposing the equivalent stretches of the three-dimensional
structures of representatives of each family. We then use the structural alignment to guide the alignment of all publicly
available RNR sequences. Our results support the hypothesis that the three RNR classes diverged from a common ancestor currently
represented by the anaerobic class III. Also, lateral transfer appears to have played a significant role in the evolution
of this protein family. 相似文献
60.