Nuclear DNA markers of the Australian tetraploid Microseris scapigera and its North American diploid relatives

The allotetraploid lactucean Microseris scapigera of Australia and New Zealand has presumably arisen in western North America by hybridization between an annual and a perennial diploid species followed by polyploidization and long-distance dispersal. A phylogenetic tree of various North American diploids, based on RFLPs in the nuclear DNA, confirmed the division of the genus into a clade containing the diploid annuals and a clade containing the diploid perennials. Four RFLP markers were shared among all accessions of M. scapigera and all the diploid accessions. Twelve markers found in the outgroup (Uropappus lindleyi) were absent in all Microseris. A cladogram of plants from six populations of M. scapigera based on eight RFLP markers shows a progressive specialization of three clades of two populations each. Two populations without any markers differentiating them from the North American diploids form the basic clade. These consist of plants with an apparently derived morphology that are self-compatible (or agamospermic) and thereby differ from most M. scapigera. Few markers in M. scapigera could be attributed to one or the other parental genome. As yet, we have found only one ITS 1 sequence of the nuclear ribosomal cistrons in M. scapigera. This sequence has features of both parental sequences.     

Fewer protective cytotoxic T-cell epitopes than T-helper-cell epitopes on vesicular stomatitis virus.

Cytotoxic T-lymphocyte (CTL) and T-helper-cell responses in various mouse strains were monitored. Protective CTL responsiveness against three proteins of vesicular stomatitis virus was H-2 linked and inducible only in half of the 15 combinations tested (each of five H-2 haplotypes combined with each of three viral proteins), whereas biologically relevant T-helper-cell responses were inducible in all. This suggests that vesicular stomatitis virus exhibits more T-helper-cell than CTL epitopes.     

CAPITULUM PHYLLOTAXIS AND NUMERICAL CANALIZATION IN MICROSERIS PYGMAEA (ASTERACEAE: LACTUCEAE)

The positions at which floret primordia arise in developing capitulum buds of Microseris pygmaea D. Don have been mapped by computer-assisted light microscopy. The primordia can be assigned positions along a basic phyllotactic spiral with a divergence angle of about 137.5°. In addition, there are regular deviations from a spiral arrangement. Typically, the first 26 primordia in phyllotactic sequence are arranged in two concentric circles of 13 primordia with considerable deviations in the divergence angle and in the distances between primordia along a parastichy at positions 13 and 26. This arrangement can be simulated by geometric models that include nearest neighbor packing, together with spiral phyllotaxis. The circular arrangement of peripheral primordia at nearly equal radial distances from the center of the developing capitulum helps to explain the numerical constancy (canalization) of peripheral structures, especially the constant number of 13 inner phyllaries on heads with very different numbers of florets.     

Niche breadth explains the range size of European-centred butterflies,but dispersal ability does not

Aim

The breadth of ecological niches and dispersal abilities have long been discussed as important determinants of species' range sizes. However, studies directly comparing the relative effects of both factors are rare, taxonomically biased and revealed inconsistent results.

Location

Europe.

Time Period

Cenozoic.

Major Taxa

Butterflies, Lepidoptera.

Methods

We relate climate, diet and habitat niche breadth and two indicators of dispersal ability, wingspan and a dispersal tendency index, to the global range size of 369 European-centred butterfly species. The relative effects of these five predictors and their variation across the butterfly phylogeny were assessed by means of phylogenetic generalized least squares models and phylogenetically weighted regressions respectively.

Results

Climate niche breadth was the most important single predictor, followed by habitat and diet niche breadth, while dispersal tendency and wingspan showed no relation to species' range size. All predictors together explained 59% of the variation in butterfly range size. However, the effects of each predictor varied considerably across families and genera.

Main Conclusions

Range sizes of European-centred butterflies are strongly correlated with ecological niche breadth but apparently independent of dispersal ability. The magnitude of range size–niche breadth relationships is not stationary across the phylogeny and is often negatively correlated across the different dimensions of the ecological niche. This variation limits the generalizability of range size–trait relationships across broad taxonomic groups.     

Regional mapping of short tandem repeats on humanchromosome 10: Cytochrome P450 gene CYP2E, D10S196, D10S220, and D10S225

Human CYP2E encodes an ethanol-inducible cytochrome P450 monooxygenase that metabolizes various carcinogens and may therefore play a role in cancer susceptibility. An intronic (GGAT)_n · (CCTA)_n repeat element was found to display limited polymorphism in Caucasoids and was used as a sequence-tagged site for genomic amplification from somatic cell hybrids to localize CYP2E to 10q24.3-qter; using the same panel, three microsatellite markers, D10S196, D10S220, and D10S225, were mapped to 10q21. The close synteny of CYP2E, CYP2C, and CYP17 belonging to two different cytochrome P450 families suggests a central role for the long arm of chromosome 10 in the evolution of this large gene superfamily.     

Identification of Ser-543 as the major regulatory phosphorylation site in spinach leaf nitrate reductase.

Spinach leaf NADH:nitrate reductase (NR) responds to light/dark signals and photosynthetic activity in part as a result of rapid regulation by reversible protein phosphorylation. We have identified the major regulatory phosphorylation site as Ser-543, which is located in the hinge 1 region connecting the cytochrome b domain with the molybdenum-pterin cofactor binding domain of NR, using recombinant NR fragments containing or lacking the phosphorylation site sequence. Studies with NR partial reactions indicated that the block in electron flow caused by phosphorylation also could be localized to the hinge 1 region. A synthetic peptide (NR6) based on the phosphorylation site sequence was phosphorylated readily by NR kinase (NRk) in vitro. NR6 kinase activity tracked the ATP-dependent inactivation of NR during several chromatographic steps and completely inhibited inactivation/phosphorylation of native NR in vitro. Two forms of NRk were resolved by using anion exchange chromatography. Studies with synthetic peptide analogs indicated that both forms of NRk had similar specificity determinants, requiring a basic residue at P-3 (i.e., three amino acids N-terminal to the phosphorylated serine) and a hydrophobic residue at P-5. Both forms are strictly calcium dependent but belong to distinct families of protein kinases because they are distinct immunochemically.     

Antiviral immune responses in mice deficient for both interleukin-2 and interleukin-4.

Antiviral immune responses of mice lacking interleukin-2 (IL-2) or IL-4 or both IL-2 and IL-4 (IL-2/4) were compared by using different viruses. Primary cytotoxic T-lymphocyte (CTL) responses against lymphocytic choriomeningitis virus (LCMV) were only moderately reduced in mice lacking IL-2 and were normal in mice lacking IL-4. Mice deficient in both interleukins exhibited variable and more strongly reduced but nevertheless in vivo protective LCMV-specific CTL responses. Similar results were obtained with vaccinia virus. Upon virus-specific restimulation in vitro, spleen cells from IL-2- and IL-2/4-deficient mice failed to generate CTL responses against virus-infected target cells, whereas the response of mice deficient in only IL-4 was comparable to that of control mice. The addition of IL-2 during in vitro restimulation completely restored the responses of both IL-2 and IL-2/4-deficient mice. T-helper-cell-independent immunoglobulin M and T-helper-cell-dependent immunoglobulin G antibody responses against vesicular stomatitis virus glycoprotein were within normal ranges for the various mutant mice. After LCMV infection, specific antibody responses against LCMV nucleoprotein were reduced four- to eightfold. These results show that mice lacking IL-2/4 have an overall tendency to exhibit more severely reduced CTL responses than IL-2- or IL-4-deficient mice. Nevertheless, and surprisingly, in vivo protective immune responses were mounted in the absence of IL-2/4, suggesting that besides a minor contribution from IL-4, other interleukins compensate in vivo for the lack of IL-2 in IL-2-deficient mice.     

Chloroplast and nuclear DNA variation among homozygous plants in a population of the autogamous annualMicroseris douglasii (Asteraceae,Lactuceae)

The autogamous diploid annualMicroseris douglasii of California occurs in many isolated populations. The populations consist of one to many highly inbred biotypes. Morphological variation among populations usually is greater than within populations. In spite of the virtual absence of gene flow even within populations, genetically determined character differences are randomly distributed and associated throughout the range of the species. Recent evidence even suggests introgression of chloroplasts from the relatedM. bigelovii. Offspring families from 25 plants of a very variable population were raised and examined for segregation of morphological and molecular (RAPD) markers. All 25 original plants were completely homozygous for all markers, but each differed from all others at least in some markers. The population consisted of two genetically isolated groups of plants: a distinct inbred line (3 plants) and 22 plants with random associations of a common set of markers and characters, possibly recombinant inbreds from a past hybridization event. One of these 22 plants contained a chloroplast genome found inM. bigelovii, the other 24 plants a chloroplast genome found only inM. douglasii.     

Immunological studies on lysosomal sphingomyelinase: Identification of a 28 000-Da component deficient in urine from patients with Niemann-Pick disease types A and B

The immunoblotting technique was used to identify sphingomyeJinase protein in samples of tissue and urine after subjection to poIyacrylamide-gel etectrophoresis in the presence of sodium dodecyl sulphate. In a sphingomyelinase preparation purified from control urine a prominent band was seen with an M_r of 28 000 Da. Glycoprotein fractions from urine and placenta, a membrane extract from spleen, and a partially purified sphingomyelinase preparation from placenta contained the 28 000-Da band plus additional, higher-M_r bands. The 28 000-Da band was detectable in urine from a patient with Niemann-Pick disease type C, but not in urine from patients with Niemann-Pick disease types A and B. It is concluded t h a t sphingomyeJinase is composed of at least one polypeptide with an M_r of 28 000 Da and that this polypeptide is deficient in the urine of patients with Niemann-Pick disease types A and B.     

Repetitive DNA in Cichorieae (Compositae)

Thermally denatured DNA of 11 species of Cichorieae (Compositae) was allowed to renature at 69° C in 0.8 M Na⁺. Two distinct fractions of repetitive DNA (fast: 10⁵ repetitions, intermediate: 10³ repetitions) were found in all species. The remaining (slow) fraction comprises 26 to 58% of the genome. The relative amounts of fast and intermediate fractions maintain constant proportions to the slow fraction except for saltatory changes, especially halvings in species with reduced genome sizes.