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- Evolution of the Fucaceae (Phaeophyceae) inferred from nrDNA-ITSPublication . Serrão, Ester; Alice, L. A.; Brawley, S. H.Sequences of the internal transcribed spacer region (ITS-1, 5.8S, and ITS-2) of nuclear ribosomal DNA were obtained from 16 species representing all six genera of Fucaceae (Ascophyllum, Fucus, Hesperophycus, Pelvetia, Pelvetiopsis, and Xiphophora) plus one outgroup (Hormosira). Parsimony analysis indicated that the family Fucaceae is monophyletic and that the northern hemisphere taxa are highly divergent from the only southern hemisphere genus, Xiphophora. The genus Pelvetia is not monophyletic because the European P. canaliculata is more closely related to Fucus, Hesperophycus, and Pelvetiopsis than to other Pelvetia species. We establish Silvetia, gen. nov. and transfer the 3 Pacific species of Pelvetia to the new genus. Fucus is monophyletic and not ancestral in the Fucaceae. The ITS sequences identified two strongly supported lineages within Fucus, one with F. serratus sister to the clade containing F. gardneri, F. distichus, and F. evanescens and a second including F. vesiculosus, F. spiralis, F. ceranoides, and F. virsoides. The ITS was not useful for resolving relationships within each of these clusters and between populations of F. vesiculosus. Within-individual variation in ITS sequences is high in Fucus, a derived genus, compared to Ascophyllum, a more ancestral genus. Mapping of the two characters that form the basis of Powell’s model for speciation in the Fucaceae showed that 1) number of eggs per oogonium has not followed a gradual reduction and that 2) monoecy/dioecy has changed several times during evolution of this family.
- U and Th isotope constraints on the duration of Heinrich events H0-H4 in the southeastern Labrador SeaPublication . C. Veiga-Pires, C.; Hillaire-Marcel, C.The duration and sequence of events recorded in Heinrich layers at sites near the Hudson Strait source area fbr ice-rafted material are still poorly constrained, notably because of the limit and uncertainties of the C-14 chronology. Here we use high-resolution Th-230-excess measurements, in a 6 m sequence raised from Orphan Knoll (southern Labrador Sea), to constrain the duration of the deposition of the five most recent Heinrich (H) layers. On the basis of maximum/minimum estimates for the mean glacial Th-230-excess flux at the studied site a minimum/maximum duration of 1.0/0.6, 1.4/0.8, 1.3/0.8, 1.5/0.9, and 2.1/1.3 kyr is obtained for H0 (similar to Younger Dryas), H1, H2, H3, and H4, respectively. Thorium-230-excess inventories and other sedimentological features indicate a reduced but still significant lateral sedimentary supply by the Western Boundary Undercurrent during the glacial interval. U and Th series systematics also provide insights into source rocks of H layer sediments (i.e., into distal Irminger Basin/local Labrador Sea supplies).
- Molecular and functional study of AQY1 from Saccharomyces cerevisiae: role of the C-terminal domainPublication . Laizé, Vincent; Gobin, R.; Rousselet, G.; Badier, C.; Hohmann, S.; Ripoche, P.; Tacnet, F.The yeast YPR192w gene, which encodes a protein (Aqy1p) with strong homology to aquaporins (AQPs), was cloned from nine S. cerevisiae strains. The osmotic water permeability coefficient (Pf) of X. laevis oocytes expressing the gene cloned from the S1278b strain (AQY1-1) was 5.7 times higher than the Pf of oocytes expressing the gene cloned from other strains (AQY1-2). Aqy1-1p, initially cloned without its C-terminus (Aqy1-1DCp), mediated an ;3 times higher water permeability than the full-length protein. This corresponds to a 3-fold higher protein density in the oocyte plasma membrane, as shown by freeze-fracture electron microscopy. Pf measurements in yeast spheroplasts confirmed the presence of functional water channels in S1278b and a pharmacological study indicated that this strain contains at least a second functional aquaporin.
- Influence of the mudflat surface shape on the green macroalgae and its associated macroepifaunaPublication . Aníbal, J.; Sprung, MartinAlthough the mudflats are relatively plain, a closer observation will show that they are a succession of mud ripples, composed by consecutive convex and concave sections. The aim of this study was to determine the influence of those sections on the dynamics of the macroalgae ulvales (Chlorophyta) and its associated macroepifauna in the Ria Formosa (a tidal lagoon on the southern coast of Portugal).