The Expanded mtDNA Phylogeny of the Franco-Cantabrian Region Upholds the Pre-Neolithic Genetic Substrate of Basques

The European genetic landscape has been shaped by several human migrations occurred since Paleolithic times. The accumulation of archaeological records and the concordance of different lines of genetic evidence during the last two decades have triggered an interesting debate concerning the role of ancient settlers from the Franco-Cantabrian region in the postglacial resettlement of Europe. Among the Franco-Cantabrian populations, Basques are regarded as one of the oldest and more intriguing human groups of Europe. Recent data on complete mitochondrial DNA genomes focused on macrohaplogroup R0 revealed that Basques harbor some autochthonous lineages, suggesting a genetic continuity since pre-Neolithic times. However, excluding haplogroup H, the most representative lineage of macrohaplogroup R0, the majority of maternal lineages of this area remains virtually unexplored, so that further refinement of the mtDNA phylogeny based on analyses at the highest level of resolution is crucial for a better understanding of the European prehistory. We thus explored the maternal ancestry of 548 autochthonous individuals from various Franco-Cantabrian populations and sequenced 76 mitogenomes of the most representative lineages. Interestingly, we identified three mtDNA haplogroups, U5b1f, J1c5c1 and V22, that proved to be representative of Franco-Cantabria, notably of the Basque population. The seclusion and diversity of these female genetic lineages support a local origin in the Franco-Cantabrian area during the Mesolithic of southwestern Europe, ∼10,000 years before present (YBP), with signals of expansions at ∼3,500 YBP. These findings provide robust evidence of a partial genetic continuity between contemporary autochthonous populations from the Franco-Cantabrian region, specifically the Basques, and Paleolithic/Mesolithic hunter-gatherer groups. Furthermore, our results raise the current proportion (≈15%) of the Franco-Cantabrian maternal gene pool with a putative pre-Neolithic origin to ≈35%, further supporting the notion of a predominant Paleolithic genetic substrate in extant European populations.     

Cyanide-resistant respiration in photosynthetic organs of freshwater aquatic plants

The rate and sensitivity to inhibitors (KCN and salicylhydroxamic acid[SHAM]) of respiratory oxygen uptake has been investigated in photosynthetic organs of several freshwater aquatic plant species: six angiosperms, two bryophytes, and an alga. The oxygen uptake rates on a dry weight basis of angiosperm leaves were generally higher than those of the corresponding stems. Leaves also had a higher chlorophyll content than stems. Respiration of leaves and stems of aquatic angiosperms was generally cyanide-resistant, the percentage of resistance being higher than 50% with very few exceptions. The cyanide resistance of respiration of whole shoots of two aquatic bryophytes and an alga was lower and ranged between 25 and 50%. These results suggested that the photosynthetic tissues of aquatic plants have a considerable alternative pathway capacity. The angiosperm leaves generally showed the largest alternative path capacity. In all cases, the respiration rate of the aquatic plants studied was inhibited by SHAM alone by about 13 to 31%. These results were used for calculating the actual activities of the cytochrome and alternative pathways. These activities were generally higher in the leaves of angiosperms. The basal oxygen uptake rate of Myriophyllum spicatum leaves was not stimulated by sucrose, malate or glycine in the absence of the uncoupler carbonylcyanide-m-chlorophenylhydrazone (CCCP), but was greatly increased by CCCP, either in the presence or in the absence of substrates. These results suggest that respiration was limited by the adenylate system, and not by substrate availability. The increase in the respiratory rate by CCCP was due to a large increase in the activities of both the cytochrome and alternative pathways. The respiration rate of M. spicatum leaves in the presence of substrates was little inhibited by SHAM alone, but the SHAM-resistant rate (that is, the cytochrome path) was greatly stimulated by the further addition of CCCP. Similarly, the cyanide-resistant rate of O₂ uptake was also increased by the uncoupler.     

Four Genes Responsible for a Position Effect on Expression from HML and HMR in Saccharomyces cerevisiae

Mating type interconversion in Saccharomyces cerevisiae occurs by transposition of copies of the a or alpha mating type cassettes from inactive loci, HML and HMR, to an active locus, MAT. The lack of expression of the a and alpha genes at the silent loci results from repression by trans-acting regulators encoded by SIR (Silent Information Regulator) genes. In this paper we present evidence for the existence of four SIR genes. Inactivation of any of these genes leads to expression of cassettes at both HML and HMR. Unusual complementation properties are observed for a number of sir mutations. Specifically, some recessive mutations in different genes fail to complement. The correspondence between SIR1, SIR2, SIR3, SIR4 and other genes with similar roles (MAR, CMT, STE8 and STE9) is presented.     

Early metabolic effects and mechanism of ammonium transport in yeast

Studies were performed to define the effects and mechanism of NH+4 transport in yeast. The following results were obtained. Glucose was a better facilitator than ethanol-H2O2 for ammonium transport; low concentrations of uncouplers or respiratory inhibitors could inhibit the transport with ethanol as the substrate. With glucose, respiratory inhibitors showed only small inhibitory effects, and only high concentrations of azide or trifluoromethoxy carbonylcyanide phenylhydrazone could inhibit ammonium transport. Ammonium in the free state could be concentrated approximately 200-fold by the cells. Also, the addition of ammonium produced stimulation of both respiration and fermentation; an increased rate of H+ extrusion and an alkalinization of the interior of the cell; a decrease of the membrane potential, as monitored by fluorescent cyanine; an immediate decrease of the levels of ATP and an increase of ADP, which may account for the stimulation of both fermentation and respiration; and an increase of the levels of inorganic phosphate. Ammonium was found to inhibit 86Rb+ transport much less than K+. Also, while K+ produced a competitive type of inhibition, that produced by NH4+ was of the noncompetitive type. From the distribution ratio of ammonium and the pH gradient, an electrochemical potential gradient of around -180 mV was calculated. The results indicate that ammonium is transported in yeast by a mechanism similar to that of monovalent alkaline cations, driven by a membrane potential. The immediate metabolic effects of this cation seem to be due to an increased [H+]ATPase, to which its transport is coupled. However, the carriers seem to be different. The transport system studied in this work was that of low affinity.     

Effects of chronic allopurinol therapy on purine metabolism in Duchenne muscular dystrophy

Adenine, adenosine, inosine, hypoxanthine, xanthosine, xanthine, guanine and guanosine blood levels in 11 Duchenne muscular dystrophy patients treated with allopurinol, 10 untreated patients and 8 healthy controls, were determined by HPLC. Serum ADA, PNP and 5'-NT were also determined. Untreated patients showed lower adenine (p less than 0.001) and higher adenosine, xanthine, ADA and PNP levels (p less than 0.01) than controls. Treated patients had lower adenine and higher xanthine levels (p less than 0.001), but higher hypoxanthine, xanthosine and guanine levels (p less than 0.001), than controls, with normal ADA and PNP. The changes observed in ADA and PNP levels suggest an involvement of these enzymes in accelerated degradation of purines in Duchenne dystrophy.     

STE16, a New Gene Required for Pheromone Production by a Cells of Saccharomyces cerevisiae

Genes required for mating by a and alpha cells of Saccharomyces cerevisiae (STE, "sterile," genes) encode products such as peptide pheromones, pheromone receptors, and proteins responsible for pheromone processing. a-specific STE genes are those required for mating by a cells but not by alpha cells. To identify new a-specific STE genes, we have employed a novel strategy that enabled us to determine if a ste mutant defective in mating as a is also defective in mating as alpha without the need to do crosses. This technique involved a strain (K12-14b) of genotype mata1 HML alpha HMR alpha sir3ts, which mates as a at 25 degrees and as alpha at 34 degrees. We screened over 40,000 mutagenized colonies derived from K12-14b and obtained 28 a-specific ste mutants. These strains contained mutations in three known a-specific genes--STE2, STE6 and STE14--and in a new gene, STE16. ste16 mutants are defective in the production of the pheromone, a-factor, and exhibit slow growth. Based on the distribution of a-specific ste mutants described here, we infer that we have identified most if not all nonessential genes that can give rise to a-specific mating defects.     

Incorporation of ionic channels from yeast plasma membranes into black lipid membranes.

Recently, patch-clamping of yeast protoplasts has revealed the presence of plasma membrane K+ channels (Gustin, M. C., B. Martinac, Y. Saimi, M. R. Culberston, and C. Kung. 1986. Science (Wash. DC). 233:1195-1197). In this work we show that fusion of purified plasma membranes into planar bilayers allows the study of the yeast channels. The main cationic conductances detected were of 64 and 116 pS, however, larger and smaller conductances have been observed. The two main conductances were sensitive to the K+ channels blockers tetraethylammonium (TEA+) and Ba2+. Bionic experiments indicated that both conductances were K+ selective.