Subcellular distribution and compartmentalization of arsenic in <Emphasis Type="Italic">Pteris vittata</Emphasis> L.

The subcellular distribution of arsenic （As） in Pteris vittata L., an As-hyperaccumniator, was studied to determine As compartmentalization and to explore the mechanisms that confer As tolerance. When the plant was grown in a nutrient solution without additional As, most of the accumulated As was isolated to the cell wall. However, in plants growing in a nutrient solution containing 0.1 or 0.2 mmol/L As, approximately 78% of the total As accumulated within the pinna. The proportions of As accumulation in the cyto- plasmic supernatant fraction were 78 % of that in the pinna and 61% of that in the plant. In either treatment group （0.1 or 0.2 mmol/L As）, the fraction containing the lowest level of As was the organelle fraction. These results suggest that As accumulates in the pinna where it is primarily distributed in the cytoplasmic supernatant fraction. The role of As compartmentalization may be intricately linked with As detoxification in P. vittata L.     

Effect of phosphorus on arsenic accumulation in As-hyperaccumulator Pteris vittata L. and its implication

Pot experiment was conducted to understand the effect of phosphorus on arsenic accumulation in As-hyperaccumulator Chinese brake (Pteris vittata L.). It is shown that arsenic concentrations in the fronds and rhizoids, the arsenic bioaccumulation factor, and the total arsenic in the fronds were not influenced significantly under low levels of phosphorus (≤400 mg/kg) and increased sharply under high levels of phosphorus (>400 mg/ kg). The discovery implies that the efficiency of arsenic removal in phytoremediation using the hyperaccumulating plant can be greatly elevated by the phosphorus addition at high rates. The interaction between the accumulation of phosphorus and that of arsenic in plant was stimulated mutually. The result represents that Chinese brake is a good material for plant physiologist to conduct comparative and mechanism studies on the uptake behaviors of phosphorus and arsenic, and phosphorus is also a potential accelerator for phytoremediation of arsenic-contaminated soils.     

Agrobacterium tumefaciens-mediated Transformation of CryⅠA(b) gene to Trichoderma harzianum

In this study, Cry ⅠA(b) gene was successfully transferred into the biocontrol fungus Trichoderma harzianum with an efficiency of 60-180 transformants per 10^6 spores by using Agrobacterium tumefaciens-mediated transformation. Putative transformants were analyzed to test the presence of Cry ⅠA(b) gene by Southern blot. Most transformants contained a single T-DNA copy. RT-PCR analysis showed that the Cry ⅠA(b) gene was transcribed. Antifungal activities and insecticidal activities of the transformants were examined. There was no obvious difference in antifungal activities between the transformants and their wild strains. The modified mortalities of the transformants T1 and T2 were 69.57% and 91.30%, respectively. The tranformation system mediated by A. tumefaciens proved to be a powerful tool for the filamentous fungi transformation and functional genomic study with its high transformation frequency, simplicity of T-DNA integration, and genetic stability of transformants.     

Fermentation of xylose to produce ethanol by recombinant <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> strain containing <Emphasis Type="Italic">XYLA</Emphasis> and <Emphasis Type="Italic">XKS1</Emphasis>

Fermentation of the pentose sugar xylose to produce ethanol using lignocellulosic biomass would make bioethanol production economically more competitive. Saccharomyce cerevisise, an efficient ethanol producer, cannot utilize xylose because it lacks the ability to convert xylose to its isomer xylulose. In this study, XYLA gene encoding xylose isomerase (XI) from Thermoanaerobacter tengcongensis MB4T and XKS1 gene encoding xylulokinase (XK) from Pichia stipitis were cloned and functionally coexpressed in Saccharomyces cerevisiae EF-326 to construct a recombinant xylose-utilizing strain. The resulting strain S. cerevisiae EF 1014 not only grew on xylose as sole carbon source, but also produced ethanol under anaerobic conditions. Fermentations performed with different xylose concentrations at different temperatures demonstrated that the highest ethanol productivity was 0.11 g/g xylose when xylose concentration was provided at 50 g/L. Under this condition, 28.4% of xylose was consumed and 1.54 g/L xylitol was formed. An increasing fermentation temperature from 30℃ to 37℃ did not improve ethanol yield.     

Genetic and physical finemapping of the Sc locus conferring indica-japonica hybrid sterility in rice （Oryza sativa L.）

Hybrid sterility is a major hindrance to utilizing the heterosis in indica-japonica hybrids. To isolate a gene Sc conferring the hybrid sterility, the locus was mapped using molecular markers and an F2 population derived from a cross between near isogenic lines. A primary linkage analysis showed that Sc was linked closely with 4 markers on chromosome 3, on which the genetic distance between a marker RG227 and Sc was 0.07 cM. Chromosome walking with a rice TAC genomic library was carried out using RG227 as a starting probe, and a contig of ca. 320 kb covering the Sc locus was constructed. Two TAC clones, M45EI4 and M90J01 that might cover the Sc locus, were partially sequenced. By searching the rice sequence databases with sequences of the TACs and RG227 a japonica rice BAC sequence, OSJNBb0078P24 was identified. By comparing the TAC and BAC sequences, six new PCR-based markers were developed. With these markers the Sc locus was further mapped to a region of 46 kb. The results suggest that the BAC OSJNBb0078P24 and TAC M45EI4 contain the Sc gene. Six ORFs were predicted in the focused 46-kb region.     

The initiation and connection of vessel elements in Arabidopsis thaliana （Brassicaceae） seedlings

This research used confocal laser scanning microscopy to examine the initiation and connection of vessel elements in Arabidopsis thaliana （L.） Heynh seedlings. The results indicated that vessel elements differentiated first in the lower portion of cotyledon-node zone （CNZ） 2 h after germination, and then extended downwards to the hypoeotyl and root and upwardly to the middle portion of CNZ. 10 h after germination, vessel elements developed in the lower portion of cotyledon blade, the second initiating site, connecting gradually with that initiated in cotyledon node and forming pinnate-marginal venation. The connection of vessel elements occurred between the upper portions of CNZ and epieotyl-shoot zone 7 d after germination. By then, the complete connection of vessel elements in the axial and lateral organs had formed.     

Biologically active <Emphasis Type="Italic">cis</Emphasis>-cinnamic acid occurs naturally in <Emphasis Type="Italic">Brassica parachinensis</Emphasis>

The biologically active cis-cinnamic acid (cis-CA) has been perceived as a synthetic plant growth regulator for decades,However,in the present study,we found that cis-CA actually exists as a naturally occurring compound in a Brassica plant,This natural growth-regulating substance presents in both the sunlight-irradiated leaf tissue and the non-irradiated root tissue ,The concentrations of cis-CA in both tissues are comparable to the bilogi-cally effective lvels of those major plant hormones,the presence of cis-CA in root tissue suggests that it may be produced through both light-dependent and -independent path-ways or it can be transproted from a plant organ to another.     

Attractiveness of tobacco volatiles induced by <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> and <Emphasis Type="Italic">Helicoverpa assulta</Emphasis> to <Emphasis Type="Italic">Campoletis chlorideae</Emphasis>

The attraction of Helicoverpa armigera-and Helicoverpa assulta-induced and mechanical damage-induced tobacco volatiles to Campoletis chlorideae was investigated, and the induced volatiles were analyzed. In windtunnel, C. chlorideae was strongly attracted by herbivoreinduced tobacco volatiles. Mechanically damaged tobacco leaves, whether treated with caterpillar regurgitant or water,were more attractive to the parasitoid than undamaged tobacco leaves. GC-MS analysis revealed that only 4 compounds were released from undamaged tobacco leaves,whereas 13 compounds were commonly emitted from herbivore-infested and mechanically damaged tobacco leaves.Compound β-pinene was specifically induced by the infestation of H. armigera, and (Z)-3-hexenal was only induced by the infestation of H. armigera and H. assulta, whereas hexyl acetate was only induced by mechanical damage. Tobacco leaves infested by H. armigera and H. assulta released larger amounts of volatiles than undamaged tobacco leaves did.Tobacco leaves treated with artificial damage plus caterpillars regurgitant or water emitted the same levels of volatiles,which were higher than that emitted by undamaged tobacco leaves. The emission amounts of single compounds were also different between differently treated plants. The differences were large between herbivore-induced and mechanical damage-induced compounds, and small between H. armigeraand H.assulta-induced compounds, and among compounds emitted from mechanically damaged plants treated with water or caterpillar regurgitant.     

Evolutionary status of<Emphasis Type="Italic">Entamoeba</Emphasis>

In addition to its medical importance as parasitic pathogen, Entamoeba has aroused people‘s interest in its evolutionary status for a long time. Lacking mitochondrion and other intracellular organelles common to typical eukaryotes, Entamoeba and several other amitochondrial protozoans have been recognized as ancient pre-mitochondriate eukaryotes and named “archezoa“, the most primitive extant eukaryotes. It was suggested that they might be living fossils that remained in a primitive stage of evolution before acquisition of organelles, lying close to the transition between prokaryotes and eukaryotes. However, recent studies revealed that Entamoeba contained an organelle, “crypton“ or “mitosome“, which was regarded as specialized or reductive mitochondrion. Relative molecular phylogenetic analyses also indicated the existence or the probable existence of mitochondrion in Entamoeba. Our phylogenetic analysis based on DNA topoisomerase Ⅱ strongly suggested its divergence after some mitchondriate enkaryotes. Here, all these recent researches are reviewed and the evolutionary status of Entamoeba is discussed.     

Effect of phosphorus on arsenic accumulation in As-hyperaccumulator Pteris vittata L. and its implication

Pot experiment was conducted to understand the effect of phosphorus on arsenic accumulation in As-hyperaccumulator Chinese brake (Pteris vittata L.). It is shown that arsenic concentrations in the fronds and rhizoids, the arsenic bioaccumulation factor, and the total arsenic in the fronds were not influenced significantly under low levels of phosphorus (≤400 mg/kg) and increased sharply under high levels of phosphorus (＞400 mg/ kg). The discovery implies that the efficiency of arsenic removal in phytoremediation using the hyperaccumulating plant can be greatly elevated by the phosphorus addition at high rates. The interaction between the accumulation of phosphorus and that of arsenic in plant was stimulated mutually. The result represents that Chinese brake is a good material for plant physiologist to conduct comparative and mechanism studies on the uptake behaviors of phosphorus and arsenic, and phosphorus is also a potential accelerator for phytoremediation of arsenic-contaminated soils.     

Comparative study of Cambrian lobopods <Emphasis Type="Italic">Miraluolishania</Emphasis> and <Emphasis Type="Italic">Luolishania</Emphasis>

The rare fossil Miraluolishania described by Liu et ah from the Lower Cambrian Chengjiang Lagerstatte in 2004 is regarded as an arthropod sphinx because it bears mosaic features of both Iobopods and arthropods. The discovery of this rare transitional form offers direct fossil evidence for exploring the relationship between Iobopods and arthropods. However, some scientists consider Miraluolishania to be a junior synonym of Luolishania because the former superficially resembles the latter in general appearance. Considering the significant differences between the two taxa, a thorough comparative study of Miraluolishania and Luolishania leads to the conclusion that there are definitely two different genera. Nevertheless, the ＂Luolishania＂ of the Haikou area is indeed ＂Miraluolishania＂, whereas Luolishania is most likely the typical genus of the Maotianshan area of Chengjiang County.     

Analysis of type II toxin-antitoxin genes <Emphasis Type="Italic">all</Emphasis> 3211-<Emphasis Type="Italic">asl</Emphasis> 3212 in <Emphasis Type="Italic">Anabaena</Emphasis> PCC 7120

The type II toxin-antitoxin genes are responsible for the phenotypic switch to a quasi-dormant state that enables cell survival under stresses, a similar function to heterocyst of cyanobacteria. In this paper, we particularly study the role of gene pair all3211-asl3212 under Spectinomycin stress to reveal how the type II toxin-antitoxin involved in environmental stress responses. Bioinformatics prediction shows that toxin protein gene All3211 is homologous to MazF, a member of mazEF family that encoding nucleases. We clone gene all3211-asl3212 into expression vectors to identify its molecular characteristics. Deletion mutant strains of all3211-asl3212 are selected in a tri-parental mating screen. Phenotype comparisons of mutant and wild type reveals no difference of single-deletion-mutants in pigment integrity, the sensitivity to antibiotics, and heterocyst formation. The results show that deletion mutation of single TAS gene pair all3211-asl3212 results in limited effects on the cellular growth of PCC 7120. Thus, we suggest that dosage compensating might be provided from redundant genes or bypass pathways to offset obvious phenotypic differences.     

<Emphasis Type="Italic">ftsZ</Emphasis> gene and plastid division

As the important cellular organelles in plants, plas-tids comprise one of the primary features that distinguish plant cells from those of other eukaryotes. Seen from the origin, plastids derive from endosymbiotic photosynthetic bacteria. Subsequently, plastids have evolved to become essential components for plant cell function. Besides the important role of chloroplasts in photosynthesis, some water-soluble proteins that involved in biosynthesis of starch, fatty acids, amino acids, nucleic aci…     

Transmembrane structure and function of dctPQM encoding C4－dicarboxylate transport proteins from nitrogen－fixing P. stutzeri A1501

C4-dicarboxylate transport proteins of diazotroph Pseudomonas stutzeri were encoded by dctPQM genes. Nucleotide sequence analysis indicated that dctP, dctQ,and dctM grouped together. Its nucleotide and amino acid sequence shared high homology with that of dctP gene encoding periplasmic C4-dicarboxylate-binding protein and dctQM genes encoding C4-dicarboxylate transport proteins from the free-living nitrogen-fixing Aotobacter vinelandii.Structural analysis showed that DctP of P. stutzeri did not include membrane-spanning regions, and DctQ and DctM contained 5 and 12 transmembrane segments, respectively.The fragment containing the complete dctPQM genes was cloned into the Tn5 transposon region of suicide mobilization plasmid pSZ2L The resultant plasmid was named pSZY6.By triparental mating, Tn5 transposon carrying the dctPQM genes inserted into the genome of the wild type strain A1501,randomly. The recombinant strain A-142 which harboured an extra copy of dctPQM genes was constructed and identified by PCR amplification of npt II gene. When A-142 was grown in minimal medium with different concentrations (20,10 and 5mmol/L) of C4-dicarboxylates succinate, malate, or fumarate as the sole carbon source, the rate of nitrogen fixation assayed by acetylene reduction was significantly higher than that of the wild-type strain A150L This result was established that an extra copy of dctPQM genes could increase the activity of nitrogen fixation of P. stutzeri strain A1501.     

Genetic diversity in the male-specific <Emphasis Type="Italic">SRY</Emphasis> gene of <Emphasis Type="Italic">Lepus yarkandensis</Emphasis>

Lepus yarkandensis, an endemic hare species in the Tarim Basin of China, has been suffering from habitat fragmentation due to desert expansion. To evaluate the effect of habitat fragmentation on its genetic diversity, the genetic diversity based on male-specific SRY gene marker is examined. A relatively low level of SRY genetic diversity is found compared to previous studies with mtDNA data, possibly due to the low SRY mutation rate and positive selection. Furthermore, one haplotype exists in eight populations along the Tarim River but not in many other relatively isolated populations, suggesting that habitat fragmentation may affect population divergence. Despite this, our pairwise Fst analysis shows no significant differentiation among populations, and this may be mainly caused by positive selection on the SRY gene in that 88 percent of individuals share the same haplotype. Finally, the phylogenetic analysis shows deep differentiation between L. yarkandensis and other two hare species (L. capensis and L. europaeus).     

Characterizations of <Emphasis Type="Italic">L</Emphasis><Subscript><Emphasis Type="Italic">p</Emphasis></Subscript>(<Emphasis Type="Italic">R</Emphasis>) using tight wavelet frames

In this paper,a Littlewood-Paley function characterization of the spaces L p(R),1相似文献