Heat treatment results in a loss of transgene-encoded activities in several tobacco lines.

Heat treatment (37 degrees C) of transgenic tobacco (Nicotiana tabacum) plants led to a reversible reduction or complete loss of transgene-encoded activities in about 40% of 10 independent transformants carrying the luciferase-coding region fused to the 355 cauliflower mosaic virus or the soybean small subunit promoter and the nopaline synthase promoter driving the neomycin phosphotransferase gene, whereas the other lines had temperature-tolerant activities. Temperature sensitivity or tolerance of transgene-encoded activities was heritable. In some of the lines, temperature sensitivity of the transgene-encoded activities depended on the stage of development, occurring in either seedlings (40% luciferase and 50% neomycin phosphotransferase) or adult plants (both 40%). The phenomenon did not correlate with copy numbers or the homo- or hemizygous state of the transgenes. In lines harboring a temperature-sensitive luciferase activity, reduction of bioluminescence was observed after 2 to 3 h at 37 degrees C. Activity was regained after 2 h of subsequent cultivation at 25 degrees C. Irrespective of the reaction to the heat treatment, the level of luciferase RNA was slightly increased at 37 degrees C. Only in lines showing temperature sensitivity of transgene-encoded activities was the amount of luciferase and neomycin phosphotransferase strongly reduced. In sterile culture, heat treatment for 15 d did not cause visible damage or changes in plant morphology. In all plants tested a slight induction of the heat-shock response was observed at 37 degrees C.     

The Schizosaccharomyces pombe cdc6 gene encodes the catalytic subunit of DNA polymerase δ

The cdc6 mutants of Schizosaccharomyces pombe have been classified as being defective in progression through the G2 phase of the cell cycle. We cloned an S. pombe gene that could complement the temperature-sensitive growth of the cdc6-23 mutant. Unexpectedly, the cloned gene was allelic to pol3, which encodes the catalytic subunit of DNA polymerase δ. Integration mapping confirmed that cdc6 and pol3 are identical. The cdc6-23 mutant carries one amino acid substitution in the conserved N3 region of Pol3. Received: 17 October 1996 / Accepted: 19 November 1996     

Externally attached radio transmitters do not affect the parental care behaviour of rock bass

Turning, pectoral fin and caudal fin rates and time spent on the nest of male rock bass Ambloplites rupestris , engaged in parental care, were not affected after the attachment of external radio transmitters. Reproductive success was similar between treatment and control fish. Micro external radio transmitters can be used on small fishes for studying parental care duration and post-care movement without altering their behaviour.     

An antigenic HIV-1 peptide sequence engineered into the surface structure of transferrin does not elicit an antibody response.

One novel approach for the biological delivery of peptide drugs is to incorporate the sequence of the peptide into the structure of a natural transport protein such as human serum transferrin (HST). However, a potential drawback is that the HST may increase the immunoreactivity of the peptide, in the same way that carrier proteins can be used to generate highly immunogenic peptide hapten conjugates. In this study we have generated a recombinant HST carrier protein that contains a peptide substrate of HIV-1 protease (VSQNYPIVL). The protein retained native HST function, and the peptide was surface exposed since it was immunoreactive in native dot blots, and was cleaved by HIV-1 protease. Immunisation of rabbits with the recombinant protein elicited only a very poor anti-peptide immune response. In contrast, strong anti-peptide immune responses were raised against both the peptide alone, and a chemical conjugate of the peptide with HST. These data demonstrate that it is possible to attenuate the immune response normally directed against an immunogenic peptide sequence by engineering into a surface exposed loop of HST. These findings may have an important impact on the future design of peptide delivery systems.     

Sexually dimorphic expression of myosin heavy chains in the adult mouse masseter.

Little is known regarding the role of androgenic hormones in the maintenance of myosin heavy chain (MHC) composition of rodent masticatory muscles. Because the masseter is the principal jaw closer in rodents, we felt it was important to characterize the influence of androgenic hormones on the MHC composition of the masseter. To determine the extent of sexual dimorphism in the phenotype of masseter muscle fibers of adult (10-mo-old) C57 mice, we stained tissue sections with antibodies specific to type IIa and IIb MHC isoforms. Females contain twice as many fibers containing the IIa MHC as males, and males contain twice as many fibers containing the IIb MHC as females. There is a modest amount of regionalization of MHC phenotypes in the mouse masseter. The rostral portions of the masseter are composed mostly of type IIa fibers, whereas the midsuperficial and caudal regions contain mostly type IIb fibers. Using immunoblots, we showed that castration results in an increase in the expression of type IIa MHC fibers in males. Ovariectomy has no effect on the fiber type composition in females. We conclude that testosterone plays a role in the maintenance of MHC expression in the adult male mouse masseter.     

Floral colour diversity in plant communities,bee colour space and a null model

Evolutionary biologists have long hypothesized that the diversity of flower colours we see is in part a strategy to promote memorization by pollinators, pollinator constancy, and therefore, a directed and efficient pollen transfer between plants. However, this hypothesis has never been tested against a biologically realistic null model, nor were colours assessed in the way pollinators see them. Our intent here is to fill these gaps. Throughout one year, we sampled floral species compositions at five ecologically distinct sites near Berlin, Germany. Bee-subjective colours were quantified for all 168 species. A model of colour vision was used to predict how similar the colours of sympatric and simultaneously blooming flowers were for bees. We then compared flower colour differences in the real habitats with those of random plant communities. We did not find pronounced deviations from chance when we considered common plants. When we examined rare plants, however, we found significant divergence in two of the five plant communities. At one site, similarly coloured species were found to be more frequent than expected, and at the other two locations, flower colours were indistinguishable from a random distribution. These results fit theoretical considerations that rare plants are under stronger selective pressure to secure pollination than common plants. Our study illustrates the power of linking such distinct biological traditions as community ecology and the neuroethology of bee vision.