EVOLUTIONARY IMPLICATIONS OF INTRASPECIFIC CHLOROPLAST DNA VARIATION IN DWARF DANDELIONS (KRIGIA; ASTERACEAE)

Intraspecific chloroplast DNA polymorphisms were examined for 51 populations of seven species in the genus Krigia. A total of 1,100 restriction sites was surveyed and 46 of these were variable at the intraspecific level. Twenty-two of the variable sites were found within K. virginica, giving this species one of the highest levels of intraspecific chloroplast DNA divergence of any examined species. In contrast, no restriction site variation was detected within K. dandelion, K. wrightii, and K. occidentalis. Five polymorphisms were identified from the 16 populations of the K. cespitosa-gracilis complex, but no mutations distinguished the K. cespitosa and K. gracilis types. Krigia montana and K. biflora showed 11 and eight restriction site polymorphisms, respectively. The chloroplast genome of the hexaploid K. montana was derived from the diploid K. biflora rather than the tetraploid K. montana. High levels of polymorphism were found in species having different ploidy levels, such as K. virginica, K. biflora, and K. montana. Furthermore, most mutations found in these three species were recorded from the tetraploid lineages. As a result, evolutionary rates between different ploidy levels differ significantly. The chloroplast DNA restriction site data suggest that all surveyed populations of the autotetraploid K. virginica originated from a common ancestor. Our results also indicate that certain regions of the chloroplast genome have changed more rapidly than others and have the potential to resolve evolutionary questions at the population level.     

RESTRICTION FRAGMENT ANALYSIS OF CHLOROPLAST DNA AND THE SYSTEMATICS OF VIGUIERA AND RELATED GENERA (ASTERACEAE: HELIANTHEAE)

Phylogenetic relationships among 31 species representing variously Helianthus, Helianthopsis, Heliomeris, Simsia, Viguiera, and Tithonia were assessed by chloroplast DNA restriction site mapping. A total of 147 mutations including 92 informative ones was detected using 16 restriction enzymes, with an estimated sequence divergence within the group of 1.4%. Parsimony analysis produced a single most parsimonious tree with a length of 161 steps and a consistency index of 0.91. Statistically significant clades, as assessed by the bootstrap method, correspond to a number of taxa recognized previously, including Helianthus (3 species), Helianthopsis (5 species), and several groups within Viguiera, including sect. Maculatae (4 species), the Baja California group (6 species), sect. Paradosa (2 species) and V. dentata (3 samples). However, species of Viguiera collectively form a highly paraphyletic group relative to species of other genera. Helianthus and Helianthopsis were separated into different clades, supporting their recent segregation. Placement of H. porteri in Helianthus rather than Heliomeris was confirmed; the single sample of the latter genus was most similar to the Baja California group of Viguiera. An expected relationship between Simsia (2 species) and one member of Viguiera ser. Grammatoglossae was confirmed (although not with two other putatively related members of Viguiera) and an unexpected relationship between Simsia and Tithonia was suggested. The presence of Mexican taxa as the more basal groups in the tree points toward a possible Mexican origin for Viguiera and related genera. A molecular clock hypothesis is rejected in many pairwise comparisons involving woody taxa with herbaceous ones, although it could not be rejected in most pairwise comparisons involving taxa of similar habit.     

Single embryo transfer in IVF to prevent multiple pregnancies.

As the success rates of IVF clinics improve, one of the adverse consequences is the increased incidence of twins, due largely to the number of embryos transferred. Even if the number of embryos transferred is restricted to two, the twinning rate can exceed 40% of the pregnancies. An obvious way to reduce this high twin rate would be to transfer only one embryo. This would require that cryopreservation of the supernumerary embryos be efficacious enough so that the chance of achieving an ongoing pregnancy is not diminished by transferring a single embryo in the stimulated cycle. Previous studies utilising embryos on day 2 and 3 of development have shown that the pregnancy rates can be acceptable (about 40%) and that the cumulative rate can be up to 60%. Most of these studies, however, do not include a comparison with the cumulative pregnancy rate with two embryos transferred in the stimulated cycle. Therefore, the efficacy has not been proven. We present clinical data from the past few years to illustrate the increase in success rates and the concomitant increase in twinning rates. The increased success in the cryopreservation program has enabled us to trial a single embryo transfer program and compare the results to the transfer of two embryos. The results strongly suggest that the transfer of a single embryo is the better clinical option.     

Gaertnera and Pagamea: Genera Within the Psychotrieae or Constituting the Tribe Gaertnereae? A Wood Anatomical and Palynological Approach

The possible alliance between Gaertnera and Pagamea (Rubiaceae-Rubioideae), two genera from the Old and New World, respectively, is investigated on the basis of wood anatomy and pollen morphology. Nowadays, the main point of discussion about the taxonomic position of these genera is whether they belong to the Psychotrieae or constitute a tribe Gaertnereae characterised by their secondarily superior ovary and sheathing stipules. Both the wood and pollen of the genus pair are found to show specific features absent in other genera of the Psychotrieae, e.g. parenchyma bands in the xylem and endexine thickenings on the polar sites of the pollen apertures. Nevertheless Gaertnera and Pagamea share many other characters with the Psychotrieae. Wood and pollen convincingly demonstrate the very close affinity of the two genera. The sister pair differs in so many features from other Psychotrieae, that Gaertnera and Pagamea should constitute at least a subtribe Gaertnerinae, formally recognized here. The general lack of profound studies on the affinities within the very large tribe Psychotrieae makes further comments on the taxonomic relationships of the Gaertnerinae difficult.     

Partial resistance to late blight (Phytophthora infestans) in hybrid progenies of four South American Solanum species crossed with diploid S. tuberosum

Resistant genotypes of the diploid tuber-bearing South American species Solarium arnezii x hondelmannii, S. berthaultii, S. leptophyes and S. microdontum were crossed with three diploid genotypes of S. tuberosum that varied in resistance and maturity type. The progenies were field tested for 2 years for resistance to a complex race of Phytophthora infestans. A wealth of genetic variation for resistance was found in most of the progenies. At least two susceptibility groups could be distinguished in some progenies of S. microdontum. This could be explained by the presence of several major resistance genes in the wild parent and, unexpectedly, in the susceptible parent SH 82-44-111. In most of the wild parents and in the susceptible parent SH 77-114-2988 there appeared to be minor resistance genes. General combining ability effects were predominant; small specific combining ability effects were detected in some crosses of S. microdontum. Gene action appeared dominant in some crosses.     

Sperm motility in the presence of boundaries

The fluid dynamics of sperm motility near both rigid and elastic walls is studied using the immersed boundary method. Simulations of both single and interacting organisms are presented. In particular, we find that nearby organisms originally undulating with a 90° phase shift may adjust their relative swimming velocities and phase-lock. Comparisons with previous analytical results are also discussed. The tendency of a near-wall to attract organisms is demonstrated.     

Susceptibility of brown trout to Gyrodactylus salaris (Monogenea) under experimental conditions

Brown trout ( Salmo trutta ) from anadromous River Lierelva, resident Lake Tunhovd, and resident Nordmarka stocks were exposed to Gyrodactylus salaris -infected salmon parr. The brown trout were fed pellets before the experiments, except for one group of the Nordmarka stock which was starved for 19 days before the experiments. The mean number of parasites declined directly and rapidly post infection for all groups of trout. There were no pronounced differences in resistance between the anadromous and the resident stocks. G. salaris infections tended to persist longer on starved than on fed trout of the Nordmarka stock. The maximum parasite persistence on trout was 50 days, and as parasite numbers increased on some fish parasite reproduction must have occurred on those trout. However, the limited susceptibility and marked innate resistance of trout to G. salaris establishment, development and reproduction, suggest parasite metapopulations will not survive on this species. Nevertheless, trout may still play a role in the dispersal of G. salaris within and between rivers.     

Regulation of insulin-like growth factor (IGF) binding protein-2 synthesis and degradation by platelet-derived growth factor and the IGFs is enhanced by serum deprivation in vascular smooth muscle cells

Growth factors such as platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF-1) stimulate proliferation and migration of vascular smooth muscle cells (SMC). IGF-l bioactivity is modulated by high-affinity binding proteins (IGFBP) which are important regulators of these processes. Procine vascular SMC synthesize IGFBP-2 and IGFBP-4 in vitro. In the present study, levels of IGFBP-2 in conditioned media (CM) were increased approximately 1.6 to 2.2-fold when cells were exposed to PDGF (20 ng.ml) or insulin (5 μg/ml) for 24 hr following a 24 hr incubation in serum-free media, or following a 72 hr exposure to either growth factor. Similar increases in IGFBP-2 mRNA levels were observed. Exposure of cells to PDGF for 24 hr without prior serum deprivation resulted in smaller (47 ± 11%) increases in IGFBP-2 protein levels but failed to alter mRNA levels. IGF-1, FGF-b? and EGF failed to increase IGFBP-2 using either experimental paradigm. In contrast, IGFBP-2 protein levels were consistently decreased (75 ± 14%) after 72 hr of exposure to IGF-II without corresponding decreases in IGFBP-2 mRNA levels. Immunoprecipitation of [³⁵S] methionine-labeled IGFBP-2 indicated that this decrease was not due to a decrease in synthesis of IGFBP-2. Immunoblot analysis of CM from cells treated with IGF-II indicated that the decrease in intact protein corresponded with an increase in two non-IGF binding IGFBP-2 fragments of 22 and 14 kD. Increased abundance of these fragements was also observed following IGF-I exposure, although corresponding decreases in intact IGFBP-2 were not usually observed. The relative abundance of these fragments did not appear to be affected by treatment with PDGF or insulin. In contrast to IGFBP-2, regulation of the levels of IGFBP-4 in CM did not appear to be altered by serum deprivation. Insulin consistently increased IGFBP-4 mRNA and protein levels under all situations. PDGF tended to increase IGFBP-4 protein levels, although this effect was less consistent and not as great as the increase observe with insulin. Treatment with IGF-I or -ll consistently decreased IGFBP-4 levels in CM but tended to increase their mRNA levels under all situations. These data indicate that insulin, PDGF, and the IGFs regulate both IGFBP-2 and IGFBP-4. While PDGF and insulin stimulate IGFBP-2 and 4 synthesis, the IGFs appear to activate protease(s) which regulate IGFBP-2 and -4 levels post-translationally. The regulation of IGFBP-2 levels by each of these mechanisms appears to be amplified by serum deprivation, but this is not observed with IGFBP-4. © 1995 Wiley-Liss, Inc.