首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 171 毫秒
1.
The comparative floral ontogeny of five species belonging to the primuloid clade of the Ericales are investigated, viz. Maesa japonica, M. perlarius, Aegiceras corniculatum, Embelia laeta and E. ribes. All five species basically show 2/5-spiral phyllotaxis of the sepal primordia, although with some minor modification (particularly in Embelia, where the flowers are predominantly tetramerous). The phyllotaxis of the common petal-stamen primordia is also 2/5-spiral in the Maesa and Aegiceras species investigated, but appears to be unidirectional in Embelia. All five species develop common petal-stamen primordia in which the resultant petal primordia are larger than the stamen primordia, and in which the stamens develop proximally on the adaxial flank of the common primordia. Growth of the placenta in Maesa and Aegiceras partially embeds the ovules, but in Embelia the ovules are almost fully immersed in placental tissue at maturity. A comprehensive review of all previously published studies of floral ontogeny of primuloid genera is presented, and the phylogenetic significance of the variation between genera is evaluated with reference to recently published cladograms.  相似文献   

2.
The growth, reproduction and condition of adults of the three dominant fish species (roach, Rutilus rutilus, (L.); perch, Perca fluviatilis, L. and ruffe, Gymnocephalus cernuus, (L.)) in the eutrophic Lake Aydat were studied over one year cycle. Compared to published data, the growth of R. rutilus and G. cernuus was about average, while that of P. fluviatilis was below average. Comparing to literature, the fecundity of R. rutilus and G. cernuus was low but their oocytes were large. In contrast, P. fluviatilis had a high fecundity but small oocytes. At the end of summer, an abrupt decrease in the condition was recorded only for perch, probably due to stress as a result of environmental conditions. The sex-ratio was in favour of females for the three studied species but, in contrast to G. cernuus, the sex-ratio of R. rutilus and P. fluviatilis increased significantly also with age. It is concluded that Lake Aydat is a more favourable environment for R. rutilus and G. cernuus than for P. fluviatilis.  相似文献   

3.
Nucleotide binding site-leucine rich repeat (NBS-LRR) proteins are encoded by a ubiquitous gene family in sunflower and frequently harbor disease resistance genes. We investigated NBS-LRR-encoding resistance gene candidates (RGCs) flanking the downy mildew resistance genes Pl 8 and Pl 14 and the rust resistance gene R Adv , which map on the NBS-LRR clusters of linkage groups 1 and 13 in sunflower genome. We shotgun sequenced bacterial artificial chromosome (BAC) clones proximal to Pl 8 , Pl 14 , and R Adv and identified seven novel non-Toll/interleukin-1 receptor (TIR)-like NBS-LRR RGCs, which clustered with previously identified RGCs of linkage group 13 but were phylogenetically distant from the TIR- and non-TIR-NBS-LRR-encoding superfamilies of sunflower. Six of the seven predicted RGCs have intact open reading frames and reside in genomic segments with abundant transposable elements. The genomic localization and sequence similarity of the novel non-TIR-like predicted RGCs suggests that they originated from tandem duplications. RGCs in the proximity of Pl 8 and R Adv were likely introgressed from silverleaf sunflower genome, where the RGC cluster of linkage group 13 is duplicated in two independent chromosomes that have different architecture and level of recombination from the respective common sunflower chromosomes.  相似文献   

4.
Summary This study investigated direct and indirect interactions between the ant, Pheidole megacephala (Fabr.), the green scale, Coccus viridis (Green), and the scale's host plant, Pluchea indica (L.). To examine the influence of ants on scales and host plants, scale population densities, scale mortality rates, and plant performance were studied on control host plants with ants and host plants from which ants had been removed. Plants with ants present had significantly greater scale population densities and scale reproductive rates than did plants without ants. Scale mortality from both parasitism and other causes was increased on plants without ants relative to plants with ants. Predator introduction experiments showed that P. megacephala removes predatory coccinellid larvae, even when they are covered with a protective coating. Host plants from which ants had been removed had significantly higher degrees of honeydew accumulation, which resulted in greater colonization by sooty mold and greater rates of leaf death and abscission. Ants also removed herbivorous lepidopteran larvae from plants. Results are discussed in terms of the potential of P. megacephala to exert direct and indirect positive effects on scale populations and an indirect positive effect on Pluchea indica.  相似文献   

5.
Numerous individuals of the poorly known species Lecithostaphylus retroflexus (Zoogonidae) and Tergestia acanthocephala (Fellodistomidae) have been recovered from the teleost fish Belone belone gracilis from off the Scandola Nature Reserve, Western Mediterranean. They are redescribed, incorporating previously undescribed features: for L. retroflexus, a post-oral ring, a bipartite seminal vesicle, the shape of the excretory vesicle, the subterminal excretory pore and the flask-shaped gland-cells associated with the distinctly pedunculate ventral sucker; and for T. acanthocephala, the intestinal bifurcation in the forebody, necessitating its return to the genus Tergestia from Theledera. Additionally, T. acanthocephala is compared with T. laticollis from various species of Trachurus from the same geographical area.  相似文献   

6.
In the present paper the chromosome complement (n = 13; 2n = 26) of the common leech Haemopis sanguisuga (L.) (Annelida: Hirudinea: Hirudinidae) was analyzed using banding techniques and fluorescent in situ hybridization (FISH) with three repetitive DNA probes [ribosomal DNA (rDNA), (TTAGGG) n and (GATA) n ]. FISH with the rDNA probe consistently mapped major ribosomal clusters (18S–28S rDNA) in the pericentromeric region of one large metacentric chromosome pair; this region, which consisted of heterochromatin rich in GC base pairs, was preferentially stained by silver nitrate (Ag-NOR). The (TTAGGG) n telomeric probe was hybridized with the termini of nearly all chromosomes, whereas the (GATA) n probe did not label any chromosome areas.  相似文献   

7.
(R)-ricinoleic acid is the main component of castor oil from Ricinus communis L. Due to the presence of the hydroxyl group in homoallylic position and asymmetrically substituted carbon atom, it may undergo a number of chemical and biochemical transformations resulting in the products with some specific bioactivities. Conversion of (R)-ricinoleic acid into its (S)-enantiomer enables synthesis of both (R)- and (S)-ricinoleic acid derivatives and comparison of their biological activities. In the present research, (R)- and (S)-ricinoleic acid amides synthesized from methyl ricinoleates and ethanolamine or pyrrolidine as well as acetate derivatives of ethanolamine amides were studied to demonstrate their biological activities using HT29 cancer cells. Double staining of cells with fluorochromes (Hoechst 33258/propidium iodide) as well as 2,′7′-dichlorodihydrofluorescein (DCF) and comet assays were performed. Both the tested amides and acetates caused DNA damage and induced apoptotic and necrotic cell death. In the case of (R)- and (S)-enantiomers of one of the tested acetates, significant difference in the ability to induce DNA damage was observed, which showed the impact of the stereogenic center on the activities of these compounds.  相似文献   

8.
Crystals of Pt(DMSO)4(TFMS)2 have been prepared by dissolution of platinum(II) hydroxide in a solution of CF3SO3H in DMSO and subsequent evaporation. The structure was determined by use of a CAD-4 diffractometer with monochromatic Mo Kα radiation. The space group is P with Z = 2, a = 8.630(2), b = 9.557(3), c = 16.659(3) Å, α = 73.33(2), β = 77.38(2) and γ = 79.19(3)°. The refinement converged to R = 0.056. The coordination around platinum is distorted square-planar with two S- and two O-bonded DMSO ligands in a cis-arrangement. The four donor atoms and the platinum are coplanar within 0.03 Å. There is a severe steric crowding between the two S-bonded DMSO molecules, which gives rise to a distortion of the bond angles around the platinum. The crowding is minimized as much as possible by a staggered arrangement of oxygen atoms and methyl groups of adjacent ligands. Pt---S bond lengths 2.208(3) and 2.205(4) Å are significantly shorter that those in the corresponding palladium complex, in accordance with a much stronger bond in the case of platinum. Bond length comparisons also indicate that ground state transinfluence of S-bonded DMSO probably is about the same in platinum and palladium complexes.  相似文献   

9.
Putative plant adhesion molecules include arabinogalactan-proteins having fasciclin-like domains. In animal, fasciclin proteins participate in cell adhesion and communication. However, the molecular basis of interactions in plants is still unknown and none of these domains have been characterized in cereals. This work reports the characterization of 34 wheat (Triticum aestivum) and 24 rice (Oryza sativa) Fasciclin-Like Arabinogalactan-proteins (FLAs). Bioinformatics analyses show that cereal FLAs share structural characteristics with known Arabidopsis FLAs including arabinogalactan-protein and fasciclin conserved domains. At least 70% of the wheat and rice FLAs are predicted to be glycosylphosphatidylinositol-anchored to the plasma membranes. Expression analyses determined from the relative abundance of ESTs in the publicly available wheat EST databases and from RNA gel blots indicate that most of these genes are weakly expressed and found mainly in seeds and roots. Furthermore, most wheat genes were down regulated by abiotic stresses except for TaFLA9 and 12 where cold treatment induces their expression in roots. Plant fasciclin-like domains were predicted to have 3-D homology with FAS1 domain of the fasciclin I insect neural cell adhesion molecule with an estimated precision above 70%. The structural analysis shows that negatively charged amino acids are concentrated along the β1-α3-α4-β2 edges, while the positively charged amino acids are concentrated on the back side of the folds. This highly charged surface distribution could provide a way of mediating protein–protein interactions via electrostatic forces similar to many other adhesion molecules. The identification of wheat FLAs will facilitate studying their function in plant growth and development and their role in stress response.Nucleotide sequence data reported are available in the DBJ/EMBL/GenBank databases under the accession numbers: TaFLA1, DQ872374; TaFLA2, DQ872375; TaFLA3, DQ872376; TaFLA4, DQ872377; TaFLA5, DQ872378; TaFLA6, DQ872379; TaFLA7, DQ872380; TaFLA8, DQ872381; TaFLA9, DQ872382; TaFLA10, DQ872383; TaFLA11, DQ872384; TaFLA12, DQ872385; TaFLA13, DQ872386; TaFLA14, DQ872387; TaFLA15, DQ872388; TaFLA16, DQ872389; TaFLA17, DQ872390; TaFLA18, DQ872391; TaFLA19, DQ872392; TaFLA20, DQ872393; TaFLA21, DQ872394; TaFLA22, DQ872395; TaFLA23, DQ872396; TaFLA24, DQ872397; TaFLA25, DQ872398; TaFL26, DQ872399; TaFLA27, DQ872400; TaFLA28, DQ872401; TaFLA29, DQ872402; TaFLA30, DQ872403; TaFLA31, DQ872404; TaAGP1, DQ872405; TaFLA33, DQ872406; TaFLA34, DQ872407. If requested the database will withhold release of data until publication.An erratum to this article can be found at  相似文献   

10.
Origin(s), evolution,and systematics ofCucurbita pepo (Cucurbitaceae)   总被引:1,自引:0,他引:1  
Numerical studies of morphological data and starch gel electrophoresis have provided a new perspective on important issues pertinent to the origin(s) and subsequent evolution of domesticatedCucurbita pepo. Wild C.texana and/orC. fraterna appear to be the most likely candidates for progenitor(s) of the domesticate. Populations of texana-like plants from beyond Texas share various attributes with Texas populations, suggesting that C. texana once had a more widespread distribution to the northeast. The possibility exists thatC. pepo was domesticated independently in eastern U.S., as well as in Mexico, which is in line with recent archeological findings. Multiple domestications are also supported by allozyme data indicating a substantial divergence within the species. A new classification consisting of C.pepo ssp.pepo (origins in Mexico),C. pepo ssp.ovifera var. ovifera (origins in eastern U.S.), and C.pepo ssp.ovifera var. texana (spontaneous populations in eastern U.S.) is proposed.  相似文献   

11.
Using a functional genomics approach, four candidate genes (PtGT34A, PtGT34B, PtGT34C and PtGT34D) were identified in Pinus taeda. These genes encode CAZy family GT34 glycosyltransferases that are involved in the synthesis of cell‐wall xyloglucans and heteromannans. The full‐length coding sequences of three orthologs (PrGT34A, B and C) were isolated from a xylem‐specific cDNA library from the closely related Pinus radiata. PrGT34B is the ortholog of XXT1 and XXT2, the two main xyloglucan (1→6)‐α‐xylosyltransferases in Arabidopsis thaliana. PrGT34C is the ortholog of XXT5 in A. thaliana, which is also involved in the xylosylation of xyloglucans. PrGT34A is an ortholog of a galactosyltransferase from fenugreek (Trigonella foenum‐graecum) that is involved in galactomannan synthesis. Truncated coding sequences of the genes were cloned into plasmid vectors and expressed in a Sf9 insect cell‐culture system. The heterologous proteins were purified, and in vitro assays showed that, when incubated with UDP‐xylose and cellotetraose, cellopentaose or cellohexaose, PrGT34B showed xylosyltransferase activity, and, when incubated with UDP‐galactose and the same cello‐oligosaccharides, PrGT34B showed some galactosyltransferase activity. The ratio of xylosyltransferase to galactosyltransferase activity was 434:1. Hydrolysis of the galactosyltransferase reaction products using galactosidases showed the linkages formed were α‐linkages. Analysis of the products of PrGT34B by MALDI‐TOF MS showed that up to three xylosyl residues were transferred from UDP‐xylose to cellohexaose. The heterologous proteins PrGT34A and PrGT34C showed no detectable enzymatic activity.  相似文献   

12.
AINTEGUMENTA (ANT) promotes initiation and growth of ovule integuments which cell fate is specified by ovule identity factors, such as SEEDSTICK (STK), SHATTERPROOF1 (SHP1) and SHATTERPROOF2 (SHP2). To study the genetic interaction between ANT and the ovule identity genes, we have obtained a stk shp1 shp2 ant quadruple mutant. The molecular and morphological characterization of the quadruple mutant and its comparison with the stk shp1 shp2 triple mutant, the shp1 shp2 ant triple mutant and the stk ant double mutant are here presented.  相似文献   

13.
Cleome viscosa is an emerging weed with the potential of interfering with okra and influencing pests of okra. Screen house studies were conducted on the phenology of C. viscosa, its interference with okra and its interaction with root-knot nematode-infected okra. Seedlings of C. viscosa were monitored in pots for growth, yield and dry matter accumulation for 14 weeks. C. viscosa was planted with okra at densities 0, 2, 4, 6, 8 and 10 weeds per okra plant and observed for 11 weeks. Data were collected on growth, yield and dry matter of okra. Plants were inoculated with 2,500 M. incognita eggs per pot while control plants were not inoculated. C. viscosa attained 91.7 cm height and accumulated 7.8 g/plant biomass at 14 weeks after planting. The percentage reduction in okra plant height, plant dry weight and fruit yield due to interference at lowest cleome density (2 plants/pot) was 33.7, 83.6 and 82.1%, respectively. Nematode reproductive factor was significantly lower for okra alone (4.9) compared to okra with cleome (7.6). This study shows that C. viscosa is a fast-growing weed that suppressed the performance of okra even at low density, is a good host to M. incognita and increased the population of the nematode in soil.  相似文献   

14.
The fixation of dien-Pt on poly(I)·poly(C) leads to only minor changes in the uv and CD spectra at ambient temperature, showing that there is little perturbation of the secondary structure in the rb range studied (up to 0.30). However, the melting profiles show two steps. The Tm for strand separation increases linearly from 61°C (rb = 0) to 80°C (rb = 0.18), after which it declines on further increasing the rb. The second melting step is not complete at 100°C, and the magnitude of the absorbance change in this second step also appears to be at a maximum at rb = 0.18. Although dien-Pt can only coordinate to one base, the nmr spectra at 80°C also show a second type of interaction with the adjacent bases, which is only destroyed in the presence of a strong denaturing agent, 5M guanidinium hydrochloride. From these results and the spectrophotometric data, we observe that dien-Pt forms a triple sandwich by hydrogen bonding of the platinum amino groups to the adjacent hypoxanthine bases (N7). The presence of these hydrogen bonds accounts for the increased stability (maximal at one Pt to three hypoxanthine bases) and their rupture is seen in the second melting step. No interaction has been observed with poly(C) strand. Reaction of dien-Pt with poly(I) shows the formation of the same triple sandwich structure in the nmr spectra.  相似文献   

15.
Abstract The karyomorphology of three species in Dipentodon (Dipentodontaceae), Perrottetia (Celastraceae), and Tapiscia (Tapisciaceae), namely Dipentodon sinicus, Perrottetia racemosa, and Tapiscia sinensis, was investigated in the present study. Recent molecular research has discovered close relationships among these three genera, which has led to the establishment of the order Huerteales with Perrottetia being placed in Dipentodontaceae. Herein we report the chromosome numbers of D. sinicus and P. racemosa for the first time, and present their karyotype formulas as 2n= 34 = 22 sm + 12 st (D. sinicus), 2n= 20 = 11 m + 9 sm (P. racemosa), and 2n= 30 = 22 m(2SAT) + 8sm (T. sinensis). Asymmetry of their karyotypes is categorized to be Type 3B in D. sinicus, Type 2A in P. racemosa, and Type 2A in T. sinensis. Each of the species shows special cytological features. Compared with Perrottetia, Dipentodon has a different basic chromosome number, a higher karyotype asymmetry, and different karyomorphology of its interphase nuclei, mitotic prophase, and metaphase. Thus, on the basis of these results, we have reservations regarding the suggestion of placing Dipentodon and Perrottetia together in the family Dipentodontaceae.  相似文献   

16.
Ulrich Ehlers 《Zoomorphology》1992,112(4):227-236
Summary The ultrastructural organization of the frontal glandular and sensory structures in aNemertoderma species and in the acoelParatomella rubra is described. In both species, a frontal gland complex with an accumulation of different body wall glands and of ciliated sensory receptors exists at the anterior tip of a specimen. Such an organization can be hypothesized as a ground pattern characteristic of the Acoelomorpha. A frontal organ with a common apical pore of many necks of mucoid glands is known for most species of the Acoela; however, such an organ is not a basic feature either of this taxon or of the Acoelomorpha. This substantiates the hypotheses of a homology of the frontal glandular structures in the Acoelomorpha and the Rhabditophora and of the monophyly of the taxon Euplathelminthes. Within the Euplathelminthes, positional, morphological and histochemical differences of the frontal glands and the secretions exist between distinct taxa. These different organizations contribute to the phylogenetic systematization of the Plathelminthes, as shown in a diagram of the phylogenetic relationships among the basic closed descendent communities of this taxon.Abbreviations e,e 1,e 2 ellipsoid granules, types 1 and 2 - ep epidermis cell - f mucoid granules - gf mucoid gland neck - is intensively staining secretions - mit mitochondria - r rod-shaped rhabdoids - sr 1 monociliated sensory receptors with vertical rootlet - sr 2 monociliated sensory receptor with rhizomelike structure - sr 3 monociliated sensory receptor with tubularlike structure - t target granules - tw terminal web  相似文献   

17.
The fixation of trans-(NH3)2Cl2 Pt(II) to poly(I)·poly(C) at low rb (< 0.05) leads to the formation of two complexed species. The major species (ca. 82% of bound platinum) involves coordination of platinum to a single hypoxanthine base, while the other species involves coordination of two hypoxanthine bases, which are either far apart on the same strand or on separate poly(I) strands, to the platinum. These same two species are found after reaction with poly(I), as are two other species throughout the entire rb range studied (rb = 0–0.30). The latter two species are assigned to trans-Pt bound to two bases on a poly(I) strand with (a) one or (b) two free bases between the two bound bases. These two species, (a) and (b), account for ca. 35% of the bound platinum, although the 1:1 species remains dominant (ca. 55%). These two additional species are observed at high rb (>0.075) after reaction with poly(I)·poly(C) but as very minor species. They are formed by reaction with melted poly(I) loops. Also at high rb, we have observed a shifted cytidine H5 resonance arising from interaction of trans-Pt with a melted loop of poly(C). Most probably, this arises from an intramolecular poly(I) to poly(C) crosslink. Results from the reaction of trans-Pt with poly(C) are presented for comparison.  相似文献   

18.
There is genetic polymorphism of the peroxidase of human saliva, but not of leukocytes. The phenotypes are determined by autosomal inheritance, the phenotype of fast mobility (SAPX 1) being determined by homozygosity for a recessive gene (SAPX 1) and the phenotypes of slow mobility (SAPX 2 and SAPX 3) being determined by two different genes, SAPX 2 and SAPX 3, with completely dominant expression at the same locus. The phenotypes are modified by varying degrees of endogenous proteolysis. The SAPX 2 and SAPX 3 types appear to be genetically controlled modifications of SAPX 1 rather than different primary gene products, because of their completely dominant inheritance, their larger molecular size compared to SAPX 1, and their dissociation with 2-mercaptoethanol to give SAPX 1. The acidic protein type Pa 1 is always found in association with SAPX 2, and an uncommon variant type Pa 2 is associated with SAPX 3. The most likely hypothesis is that the genes Pa 1 and Pa 2 produce products which modify the SAPX 1 type. When the Pa type is Pa 0, the SAPX phenotype is SAPX 1. Since 2-mercaptoethanol can dissociate the Pa 1 protein into a probable monomeric form, and can dissociate SAPX 2 and SAPX 3 to give SAPX 1, it is probable that Pa 1 and Pa 2 monomers complex with SAPX 1 through disulfide bonds to give SAPX 2 or SAPX 3 types. The frequencies of the genes determining the SAPX types are the same as those for Pa: SAPX 1 and Pa 0=0.787, SAPX 2 and Pa 1=0.208, SAPX 3 and Pa 2=0.005.This study was supported by a grant from the National Institutes of Dental Research (2-RO1-DE-03658-11).  相似文献   

19.
Phenylalanine ammonia-lyase and cinnamate 4-hydroxylase are important enzymes in allocating significant amounts of carbon from phenylalanine into the biosynthesis of several important secondary metabolites. Tea is an important crop of commerce known for its beverage and medicinally important flavonoid compounds, mainly catechins. As metabolic flux for the operation of the flavonoid pathway is maintained through the activities of PAL and C4H, thus, catechins biosynthesis in tea is critically dependent on the products of these enzymes. We examined the expression of PAL and C4H. Sequence encoding CsPAL was isolated from tea by polymerase chain reaction using sequence information available at the NCBI GenBank. Sequence encoding C4H was isolated from tea by using differential display of mRNA and rapid amplification of cDNA ends technology. CsC4H (AY641731) comprised of 1,352 bp full-length cDNA with open reading frame of 1,173 bp encoding 390 amino acids. Catechin contents decreased in response to drought stress (DS), abscisic acid (ABA), and gibberellic acid (GA3) treatments but increased in response to wounding. The expression of CsPAL and CsC4H showed the same behavior under the above treatments and was also in accordance with the catechin contents. A positive correlation between catechin contents and gene expression suggested a critical role of the enzymes in catechins biosynthesis and a crosstalk between phenylpropanoid and flavonoid pathways.  相似文献   

20.
Tunneling behavior of laboratory-maintained cultures of Reticulitermes flavipes (Kollar) and R. virginicus (Banks) was examined to determine (1) if the termites build tunnels along preexisting wires or tunnels, and (2) whether tunnels are arranged to optimize search efficiency. Tunnel patterns were considered optimal if, for the number of tunnels present, the maximum area was explored. Termites entered either control arenas or arenas in which they encountered a wire or a pre-formed tunnel. Analyses revealed that R. flavipes and R. virginicus almost always follow pre-formed tunnels, but do not follow wires as readily. Within each species, the distributions of tunnels in treatment arenas were different from distributions in control arenas, most often when pre-formed tunnels were the treatment. Optimal tunnel arrangements in control arenas were found in 62% of R. flavipes patterns with 2 tunnels and in 43% of R. virginicus patterns with 2 tunnels. None of the 3-tunnel patterns from control arenas of R. flavipes and 29% of those of R. virginicus had optimal arrangements. Overall, the spatial arrangement of tunnels in control arenas was significantly different between R. flavipes and R. virginicus.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号