Immunochemical comparison of membrane-associated and secreted arabinogalactan-proteins in rice and carrot

Arabinogalactan-proteins (AGPs) occurring in suspension-cultured rice (Oryza saliva L.) cells, their conditioned medium and at the rice root apex were investigated using monoclonal antibodies and the AGP-binding -glucosyl Yariv reagent ( GlcY). A monoclonal antibody, LM2, was generated that recognized an acidic carbohydrate epitope common to two soluble AGPs occurring in the conditioned medium of proliferating rice cells, membrane-associated AGPs (rmAGP) in the cultured cells and two AGPs at the rice root apex. In addition, LM2 recognized AGPs secreted by suspensioncultured carrot (Daucus carota L.) cells. The two AGPs of the rice culture medium, srAGP1 and srAGP2, were discriminated by their mobilities during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, reaction with GlcY, the presence of arabinogalactan epitopes and anion-exchange chromatography. The association of rmAGP with the plasma membrane was investigated by Triton-X-114/aqueous partitioning of both microsomal and plasma-membrane preparations and rmAGP was found to partition into the detergent phase, indicating that AGPs are hydrophobic plasma-membrane proteins in rice. This was in contrast to plasma-membrane AGPs of suspension-cultured carrot cells that partitioned into the aqueous phase. At the rice root apex most of the AGP was associated with the microsomal fraction and also partitioned into the detergent phase, although a distinct highmolecular-mass AGP entered the aqueous phase.Abbreviations AGP arabinogalactan-protein - GlcY -glucosyl Yariv reagent - ELISA enzyme-linked immunosorbent assay We gratefully acknowledge support from the Leverhulme Trust, the UK Biotechnology and Biological Sciences Research Council and the Royal Society.     

Refinement of the Van der Woude Gene Location and Construction of a 3.5-Mb YAC Contig and STS Map Spanning the Critical Region in 1q32–q41

Van der Woude syndrome (VWS) is the most frequent form of syndromic clefting. Linkage analysis has localized the gene between D1S245 and D1S414, an interval of 4.1 cM with the following order of loci: centromere–D1S245/D1S471–D1S491–D1S205–D1S414–telomere. A microdeletion around D1S205 aided in narrowing the critical region to D1S491–D1S414 by heterozygosity testing. In this study, the location was refined by detection of a recombinant with D1S205 in a new family, indicating that VWS lies between D1S491 and D1S205, a 1.6-cM interval. A roughly 3.5-Mb YAC contig was built from D1S245 through D1S414, encompassing the interval D1S491–D1S205 in level 1 or level 2 paths. Clones were assembled by sequence tagged site (STS) content using the five polymorphic markers from above, four novel STSs identified from YAC ends, and a new STS derived from probe CRI-L461 (D1S70). D1S70 was assigned to the critical region. One single YAC, yCEPH785B2, contains both flanking STSs (D1S491, D1S205). STS content mapping suggests neither chimerism nor deletion of yCEPH785B2 but does suggest that the maximum size of the critical region is approximately 850 kb. All STSs were tested for their presence on a somatic cell hybrid containing the microdeleted chromosome 1 as the sole human chromosome 1 component. Both the proximal and distal ends of the microdeletion mapped to the 850-kb YAC, yCEPH785B2. Therefore, the microdeletion overlapped the critical region, confirming the genetic recombinant data.     

Identification of molecular markers in soybean comparing RFLP,RAPD and AFLP DNA mapping techniques

Three different DNA mapping techniques—RFLP, RAPD and AFLP—were used on identical soybean germplasm to compare their ability to identify markers in the development of a genetic linkage map. Polymorphisms present in fourteen different soybean cultivars were demonstrated using all three techniques. AFLP, a novel PCR-based technique, was able to identify multiple polymorphic bands in a denaturing gel using 60 of 64 primer pairs tested. AFLP relies on primers designed in part on sequences for endonuclease restriction sites and on three selective nucleotides. The 60 diagnostic primer pairs tested for AFLP analysis each distinguished on average six polymorphic bands. Using specific primers designed for soybean fromEco RI andMse I restriction site sequences and three selective nucleotides, as many as 12 polymorphic bands per primer could be obtained with AFLP techniques. Only 35% of the RAPD reactions identified a polymorphic band using the same soybean cultivars, and in those positive reactions, typically only one or two polymorphic bands per gel were found. Identification of polymorphic bands using RFLP techniques was the most cumbersome, because Southern blotting and probe hybridization were required. Over 50% of the soybean RFLP probes examined failed to distinguish even a single polymorphic band, and the RFLP probes that did distinguish polymorphic bands seldom identified more than one polymorphic band. We conclude that, among the three techniques tested, AFLP is the most useful.     

Growth of food-borne pathogenic bacteria in oil-in-water emulsions: I—Methods for investigating the form of growth

Methods are presented for investigating the site and form of growth of bacteria in model oil-in-water emulsions and in dairy cream. Following growth of the bacteria, the continuous aqueous phase is gelled using agarose and the oil phase removed using a mixture of chloroform and methanol. Using this method, the authors have found that Listeria monocytogenes, Salmonella typhimurium and Yersinia enterocolitica grow in the form of colonies in concentrated oil-in-water emulsions. Colonies of L. monocytogenes and Y. enterocolitica also form in artificially-inoculated fresh and tinned dairy cream. If information about the precise site of growth is not required, the authors have discovered that intact colonies can be liberated from the model emulsions by dissolving away the oil phase with chloroform: methanol.     

Nesting Behaviour of Abert Squirrels (Sciurus aberti)

Nesting behaviour of Abert squirrels (Sciurus aberti), including site selection and use, was studied in the foothills of the Rocky Mountains in Boulder County, Colorado. Only females were observed building nests, although both males and females maintained nests once they were built. Communal nesting by Abert squirrels was rare, but the majority of observed nest sharings involved unrelated male and female pairs. A total of 14 variables were used to evaluate the nests (n = 49) inhabited by Abert squirrels from May 1988 to Jun. 1991. All nests were located in Ponderosa pine (Pinus ponderosa) trees. The majority of nests were constructed of twigs and located in the upper one-third of the canopy, near the trunk, on the south-east side of the tree. Trees with nests were predominantly located in closed stands. Nest trees, when compared with unused control trees that were equally accessible to squirrels, were significantly different from control trees in five of nine variables. Nest tree crowns intertwined with a larger number of adjacent tree crowns than did control tree crowns. Nest trees were also significantly taller than control trees, but subdominant to adjacent trees within a stand. Seasonal and diurnal patterns of nest use indicate that Abert squirrels do not choose nest locations on the south-east sides of trees to facilitate behavioural thermoregulation. Rather, Abert squirrels select nest site locations to (1) maximize accessibility and (2) maximize structural stability which may provide protection from wind and rain.     

Familial Site-specific Ovarian Cancer Is Linked to BRCA1 on 17q12-21

In a study of nine families with “site-specific” ovarian cancer (criterion: three or more cases of epithelial ovarian cancer and no cases of breast cancer diagnosed at age <50 years) we have obtained evidence of linkage to the breast-ovarian cancer susceptibility gene, BRCA1 on 17q12-21. If the risk of cancer in these families is assumed to be restricted to the ovary, the best estimate of the proportion of families linked to BRCA1 is .78 (95% confidence interval .32–1.0). If predisposition to both breast and ovarian cancer is assumed, the proportion linked is 1.0 (95% confidence interval .46–1.0). The linkage of familial site-specific ovarian cancer to BRCA1 indicates the possibility of predictive testing in such families; however, this is only appropriate in families where the evidence for linkage to BRCA1 is conclusive.     

Carbon integration in Plantago aristata (Plantaginaceae): the reproductive effects of defoliation

Patterns of carbon integration in aclonal species are poorly understood in spite of their potential to influence individual fitness. To provide more information about these patterns, we performed a defoliation experiment with P. aristata. We examined, at the metameric level, the reproductive responses to the removal of the major carbon sources within metamers. Bracts on marked reproductive spikes and leaves subtending these spikes were removed at three stages of reproductive maturity: spike elongation, flowering, and fruiting. Spike dry weight and length, capsule number, seeds per capsule, and seed weight were measured. We tested the hypothesis that seed weight would respond least to defoliation. We also performed a complementary ¹⁴C translocation experiment to measure the amount of radioactive carbon moving into the marked spikes from outside the metamer. Defoliation depressed all components of reproduction within marked spikes, and little ¹⁴C was translocated from outside the metamer into the reproductive spikes, even those that were defoliated. Both results support the view that reproductive metamers in this species are largely autonomous with respect to their carbon budget. Defoliation during spike elongation most depressed reproduction, and bract removal depressed reproduction more than did leaf removal. The data suggest that bracts compensate for leaf removal by increasing their photosynthetic rate; however, the ability to compensate differs among plant populations. Of all the reproductive components, seed weight was least affected by defoliation. The data show, however, that the time of defoliation relative to reproductive development influences which reproductive components are affected.     

Diel Migrations of Microorganisms within a Benthic, Hypersaline Mat Community

We studied the diel migrations of several species of microorganisms in a hypersaline, layered microbial mat. The migrations were quantified by repeated coring of the mat with glass capillary tubes. The resulting minicores were microscopically analyzed by using bright-field and epifluorescence (visible and infrared) microscopy to determine depths of coherent layers and were later dissected to determine direct microscopic counts of microorganisms. Microelectrode measurements of oxygen concentration, fiber optic microprobe measurements of light penetration within the mat, and incident irradiance measurements accompanied the minicore sampling. In addition, pigment content, photosynthesis and irradiance responses, the capacity for anoxygenic photosynthesis, and gliding speeds were determined for the migrating cyanobacteria. Heavily pigmented Oscillatoria sp. and Spirulina cf. subsalsa migrated downward into the mat during the early morning and remained deep until dusk, when upward migration occurred. The mean depth of the migration (not more than 0.4 to 0.5 mm) was directly correlated with the incident irradiance over the mat surface. We estimated that light intensity at the upper boundary of the migrating cyanobacteria was attenuated to such an extent that photoinhibition was effectively avoided but that intensities which saturated photosynthesis were maintained through most of the daylight hours. Light was a cue of paramount importance in triggering and modulating the migration of the cyanobacteria, even though the migrating phenomenon could not be explained solely in terms of a light response. We failed to detect diel migration patterns for other cyanobacterial species and filamentous anoxyphotobacteria. The sulfide-oxidizing bacterium Beggiatoa sp. migrated as a band that followed low oxygen concentrations within the mat during daylight hours. During the nighttime, part of this population migrated toward the mat surface, but a significant proportion remained deep.