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991.
The transmitting-tissue cells of the style of flowering plants secrete a complex extracellular matrix through which pollen tubes grow to the ovary to effect fertilisation. This matrix is particularly rich in a class of proteoglycans, the arabinogalactan-proteins (AGPs). AGPs from the ovary of Nicotiana alata were found to be developmentally regulated, as the different charge classes of AGPs altered during floral development. The AGPs from the mature ovary had charge characteristics that were distinct from those previously reported for the stigma and style. However, the concentration of AGP (0.6 g/ml fresh weight) in the ovary did not change during development, or in response to either compatible or incompatible pollination. The AGPs of the ovary are mainly associated with the epidermis of the placenta. 相似文献
992.
993.
David M. Lonsdale Lisa J. Moisan Alison J. Harvey 《Plant Molecular Biology Reporter》1995,13(4):343-345
We have designed and constructed a series of plasmid vectors based on pBlueScript, where additional restriction sites have
been incorporated into theSstI andKpn I sites. These sites, of enzymes that cut only rarely, permit expression cassettes constructs to be easily excised and multimerized
with others. 相似文献
994.
Paula A. Clark Tracy Lester Sally Genet Alison M. Jones Rudi Hendriks Roland J. Levinsky Christine Kinnon 《Human genetics》1995,96(4):427-432
Mutations in the common gamma chain (c or IL2RG) of the interleukin-2, –4, –7, –9 and –15 receptors have been found to cause X-linked severe combined immunodeficiency (SCIDX1). We report here on the mutations identified in a further ten families. Two of the mutations identified have occurred twice in unrelated families, indicating two possible mutational hotspots. Seven of the mutations, which were identified by single-strand conformational polymorphism (SSCP) analysis, are point mutations, and the eighth is a small deletion. We also report on the first use of assays based on these mutations within IL2RG for unambiguous carrier determination. The consequences for the c proteins produced as a result of these mutations are discussed. 相似文献
995.
Paul R. Martin Alison A. Watson Thomas F. McCaul John S. Mattick 《Molecular microbiology》1995,16(3):497-508
The opportunistic pathogen Pseudomonas aeruginosa produces type 4 fimbriae which promote adhesion to epithelial cells and are associated with a form of surface translocation called twitching motility. Transposon mutagenesis was used to identify loci required for fimbrial assembly or function by screening for mutants that lack the spreading colony morphology characteristic of twitching motility. Six mutants were isolated that contain transposon insertions upstream of the previously characterized gene pilQ. This region contains four genes: pilM-P, which encode proteins with predicted sizes of 37.9, 22.2, 22.8 and 19.0 kDa, respectively, pilM-P appear to form an operon and to be expressed from a promoter in the intergenic region between pilM and the divergently transcribed upstream gene ponA. PilM-P were found to be required for fimbrial biogenesis by complementation studies using twitching motility and sensitivity to fimbrial-specific phage as indicators of the presence of functional fimbriae. This was confirmed by electron microscopy. PilO and PilP did not have homologues in the sequence databases, but the predicted PilN amino acid sequence displayed similarity to XpsL from Xanthamonas campestris, a protein required for protein secretion. PilP contained a hydro-phobic leader sequence characteristic of lipoproteins, while PilN and PilO have long internal hydrophobic domains which may serve to localize them to the cytoplasmic membrane. PilM has shared sequence motifs with the cell division protein FtsA from Bacillus subtilis and Escherichia coli, as well as the rod-shapedetermining protein MreB from E. coli. These motifs are also conserved in eukaryotic actin, in which they are involved in forming an ATPase domain. Deletion mutants of pilM and pilQ displayed a dominant negative phenotype when transformed into wild-type cells, suggesting that these genes encode proteins involved in multimeric structures. 相似文献
996.
Thomas Altmann Gisela Felix Alison Jessop Annette Kauschmann Ursula Uwer Hugo Pe?a-Cortés Lothar Willmitzer 《Molecular & general genetics : MGG》1995,247(5):646-652
Using a two-component Ac/Ds system consisting of a stabilized Ac element (Acc1) and a non-autonomous element (DsA), 650 families of plants carrying independent germinal DsA excisions/transpositions were isolated. Progenies of 559 of these Acc1/DsA families, together with 43 families of plants selected for excision/transposition of wild-type (wt)Ac, were subjected to a broad screening program for mutants exhibiting visible alterations. This resulted in the identification of 48 mutants showing a wide variety of mutant phenotypes, including embryo lethality (24 mutants), chlorophyll defects (5 mutants), defective seedlings (2 mutants), reduced fertility (5 mutants), reduced size (3 mutants), altered leaf morphology (2 mutants), dark green, unexpanded rosette leaves (3 mutants), and aberrant flower or shoot morphology (4 mutants). To test whether these mutants were due to transposon insertions, a series of Southern blot experiments was performed on 28 families, comparing in each case several mutant plants with others showing the wild-type phenotype. A preliminary analysis revealed in 4 of the 28 families analyzed a common, novel DsA fragment in all mutant plants, which was present only in heterozygous plants with wt phenotype, as expected for DsA insertion mutations. These four mutants included two showing embryo lethality, one with dark green, unexpanded rosette leaves and stunted inflorescences, and one with curly growth of stems, leaves and siliques. Further evidence for DsA insertion mutations was obtained for one embryo lethal mutant and for the stunted mutant, while in case of the second embryo lethal mutant, the DsA insertion could be separated from the mutant locus by genetic recombination. 相似文献
997.
The fate of 15N-labelled nitrate additions to a northern hardwood forest in eastern Maine,USA 总被引:5,自引:0,他引:5
Knute J. Nadelhoffer Martha R. Downs Brian Fry John D. Aber Alison H. Magill Jerry M. Melillo 《Oecologia》1995,103(3):292-301
We followed the movements of 15N-labelled nitrate additions into biomass and soil pools of experimental plots (15×15 m each) in a mid-successional beech-maple-birch-spruce forest in order to identify sinks for nitrate inputs to a forest ecosystem. Replicate plots (n=3) were spray-irrigated with either 28 or 56 kg N ha–1 year–1 using 15N-labelled nitric acid solutions (15N = 344 ) during four successive growing seasons (April–October). The 15N contents of foliage, bolewood, forests floor and mineral soil (0–5 cm) increased during the course of treatments. Mass balance calculations showed that one-fourth to one-third of the nitrate applied to forest plots was assimilated into and retained by above ground plant tissues and surface soil horizons at both rates of nitrate application. Plant and microbial assimilation were of approximately equal importance in retaining nitrate additions to this forest. Nitrate use among tree species varied, however, with red spruce showing lower rates of nitrate assimilation into foliage and bolewood than American beech and other deciduous species. 相似文献
998.
Sedigheh Alizadeh Peter J. Nixon Alison Telfer James Barber 《Photosynthesis research》1995,43(2):165-171
A rapid procedure has been developed for the isolation of the photosystem two reaction centre complex (PS II RC) from a double mutant of Chlamydomonas reinhardtii, F54-14, which lacks the Photosystem one complex and the chloroplast ATPase. Thylakoid membranes are solubilised with 1.5% (w/v) Triton X-100 and the PS II RC purified by anion-exchange chromatography using TSK DEAE-650(S) (Merck). The complex has a pigment stoichiometry of approximately six chlorophyll a: two pheophytin a: one cytochrome b-559: one to two -carotene. It photoaccumulates reduced pheophytin and oxidised P680 in the presence of sodium dithionite and silicomolybdate, respectively. Immunoblotting experiments have confirmed the presence of the D1 and D2 polypeptides in this complex. The -subunit of cytochrome b-559 was identified by N-terminal sequencing. Comparison of the complex with the PS II RC from pea using SDS-polyacrylamide gel electrophoresis showed that their polypeptide compositions were similar. However, the -subunit of cytochrome b-559 from C. reinhardtii has a lower apparent molecular weight than the pea counterpart whereas the -subunit is larger.Abbreviations DM
n-dodecyl -d-maltoside
- RC
reaction centre
- SiMo
silicomolybdate, SiMo12O40
4–
- TAP
Tris-acetate-phosphate 相似文献
999.
Functional analysis of a gibberellin-regulated wheat -amylase promoter, -Amy2/54, has indicated that three regions were essential for expression. By studying the ability of mutant promoters, containing a randomly inserted 22 bp excision linker, to direct expression in oat aleurone protoplasts we have refined the positions and extents of these three cis elements and also demonstrated the presence of two additional elements. By converting the linker insertions to either single base point mutations or deletions using the class IIS restriction endonuclease Bsm I we have shown that nucleotides –119 and –109 within the GARE –121GTAACAGAGTCTGG–108 and nucleotide –152 within the proposed element –156GATTGACTTGACC–144 are essential for high level expression from this promoter. 相似文献
1000.
Martin E. Cannell Alison J. Mitchell Sharon McCready James A. Callow Jonathan R. Green 《Plant molecular biology》1995,27(4):821-824
A monoclonal antibody (MAb UB42) is described that binds to thylakoids in pea chloroplasts, as shown by EM-immunogold labelling. The antibody recognised proteins of ca. 23–29 kDa in western blots of a pea leaf homogenate. A cDNA library was prepared from pea epidermal cells in the vector ZAP II, and immunoscreening of the library with UB42 led to the isolation of a clone, pUB42. This was sequenced and had an open reading frame of 269 codons encoding a predicted polypeptide of 28.9 kDa. The sequence showed extensive homology with three closely related polypeptides belonging to a family of chlorophyll a/b-binding proteins from the light harvesting complex of photosytem I (LHCI). Collectively, the results suggest that MAb UB42 recognises an epitope on the type II chlorophyll a/b-binding protein from LHCI and that clone pUB42 encodes this protein. 相似文献