Ocean acidification leads to counterproductive intestinal base loss in the gulf toadfish (opsanus Beta)

Abstract Oceanic CO(2) has increased from 280 to 380 μatm since preindustrial times and is expected to reach 1,900 μatm by 2300. In addition, regional upwelling zones exhibit levels up to 2,300 μatm, making exploration at future global projected CO(2) levels ecologically relevant today. Recent work has demonstrated that CO(2) exposure as low as 1,000 μatm induces acidosis in toadfish (Opansus beta), leading to metabolic compensation by retention of blood [Formula: see text] in an effort to defend pH. Since increased serosal [Formula: see text] translates to increased [Formula: see text] secretion rates in isolated intestinal tissue, we predicted that blood elevation of [Formula: see text] and Pco(2) during exposure to 1,900 μatm CO(2) would increase in vivo base secretion rates. Rectal fluid and CaCO(3) excretions were collected from toadfish exposed to 380 (control) and 1,900 μatm CO(2) for 72 h. Fluids were analyzed for pH, osmolality, ionic composition, and total CO(2). Precipitated CaCO(3) was analyzed for titratable alkalinity, Mg(2+), and Ca(2+) content. Fish exposed to 1,900 μatm CO(2) exhibited higher rectal base excretion rates, higher rectal fluid [Formula: see text] (mmol L(-1)), and lower fluid Cl(-) (mmol L(-1)) than controls, suggesting increased intestinal anion exchange as a result of the compensated respiratory acidosis. This study verifies that imminent projected CO(2) levels expected by the year 2300 lead to greater intestinal [Formula: see text] loss, a process that acts against compensation for a CO(2)-induced acidosis.     

Female, but not male, tropical sparrows respond more strongly to the local song dialect: implications for population divergence

In addition to the observed high diversity of species in the tropics, divergence among populations of the same species exists over short geographic distances in both phenotypic traits and neutral genetic markers. Divergence among populations suggests great potential for the evolution of reproductive isolation and eventual speciation. In birds, song can evolve quickly through cultural transmission and result in regional dialects, which can be a critical component of reproductive isolation through variation in female preference. We examined female and male behavioral responses to local and nonlocal dialects in two allopatric populations of rufous-collared sparrows (Zonotrichia capensis) in the Andes Mountains of Ecuador. Here we show that female sparrows prefer their natal song dialect to the dialect of an allopatric population that is just 25 km away and separated by an unsuitable higher-elevation habitat (pass of 4,200 m), thus providing evidence of prezygotic reproductive isolation among populations. Males showed similar territorial responses to all conspecific dialects with no consistent difference with respect to distance, making male territoriality uninformative for estimating reproductive isolation. This study provides novel evidence for culturally based prezygotic isolation over very short distances in a tropical bird.     

The Poisson Index: a new probabilistic model for protein ligand binding site similarity

MOTIVATION: The large-scale comparison of protein-ligand binding sites is problematic, in that measures of structural similarity are difficult to quantify and are not easily understood in terms of statistical similarity that can ultimately be related to structure and function. We present a binding site matching score the Poisson Index (PI) based upon a well-defined statistical model. PI requires only the number of matching atoms between two sites and the size of the two sites-the same information used by the Tanimoto Index (TI), a comparable and widely used measure for molecular similarity. We apply PI and TI to a previously automatically extracted set of binding sites to determine the robustness and usefulness of both scores. RESULTS: We found that PI outperforms TI; moreover, site similarity is poorly defined for TI at values around the 99.5% confidence level for which PI is well defined. A difference map at this confidence level shows that PI gives much more meaningful information than TI. We show individual examples where TI fails to distinguish either a false or a true site paring in contrast to PI, which performs much better. TI cannot handle large or small sites very well, or the comparison of large and small sites, in contrast to PI that is shown to be much more robust. Despite the difficulty of determining a biological 'ground truth' for binding site similarity we conclude that PI is a suitable measure of binding site similarity and could form the basis for a binding site classification scheme comparable to existing protein domain classification schema.     

Kinetic and stereochemical analysis of YwhB, a 4-oxalocrotonate tautomerase homologue in Bacillus subtilis: mechanistic implications for the YwhB- and 4-oxalocrotonate tautomerase-catalyzed reactions

YwhB, a 4-oxalocrotonate tautomerase (4-OT) homologue in Bacillus subtilis, has no known biological role, and the gene has no apparent genomic context. The kinetic and stereochemical properties of YwhB have been examined using available enol and dienol compounds. The kinetic analysis shows that YwhB has a relatively nonspecific 1,3- and 1,5-keto-enol tautomerase activity, with the former activity prevailing. Replacement of Pro-1 or Arg-11 with an alanine significantly reduces or abolishes these activities, implicating both residues as critical ones for the activities. In D2O, ketonization of two monoacid substrates (2-hydroxy-2,4-pentadienoate and phenylenolpyruvate) produces a mixture of stereoisomers {2-keto-3-[2H]-4-pentenoate and 3-[2H]-phenylpyruvate}, where the (3R)-isomers predominate. Ketonization of 2-hydroxy-2,4-hexadienedioate, a diacid, in D2O affords mostly the opposite enantiomer, (3S)-2-oxo-[3-2H]-4-hexenedioate. The mono- and diacids apparently bind in different orientations in the active site of YwhB, but the highly stereoselective nature of the YwhB reaction using a diacid suggests that the biological substrate for YwhB may be a diacid. Moreover, of the three dienols examined, 1,3- and 1,5-keto-enol tautomerization reactions are only observed for 2-hydroxy-2,4-hexadienedioate, indicating that the C-3 and C-5 positions are accessible for protonation in this compound. Incubation of 4-OT with 2-hydroxy-2,4-hexadienedioate in D2O results in a racemic mixture of 2-oxo-[3-2H]-4-hexenedioate, suggesting that 4-OT may not catalyze a 1,3-keto-enol tautomerization reaction using this dienol. It has previously been shown that 4-OT catalyzes the near stereospecific conversion of 2-hydroxy-2,4-hexadienedioate to (5S)-[5-2H]-2-oxo-3-hexenedioate in D2O. Taken together, these observations suggest that 4-OT might function as a 1,5-keto-enol tautomerase using 2-hydroxy-2,4-hexadienedioate.     

Insight into the mechanism of dopamine D1-like receptor activation. Evidence for a molecular interplay between the third extracellular loop and the cytoplasmic tail

A chimeric D1A dopaminergic receptor harboring the cytoplasmic tail (CT) of the D1B subtype (D1A-CTB) has been used previously to show that CT imparts high dopamine (DA) affinity and constitutive activity to the D1B receptors. However, the D1A-CTB chimera, unlike the D1B subtype, exhibits a significantly lower DA potency for stimulating adenylyl cyclase and a drastically lower maximal binding capacity (Bmax). Here, using a functional complementation of chimeric D1-like receptors, we have identified the human D1B receptor regions regulating the intramolecular relationships that lead to an increased DA potency and contribute to Bmax. We demonstrate that the addition of variant residues of the third extracellular loop (EL3) of the human D1B receptor into D1A-CTB chimera leads to a constitutively active mutant receptor displaying an increased DA affinity, potency, and Bmax. These results strongly suggest that constitutively active D1-like receptors can adopt multiple active conformations, notably one that confers increased DA affinity with decreased DA potency and Bmax and another that imparts increased DA affinity with a strikingly increased DA potency and Bmax. Overall, we show that a novel molecular interplay between EL3 and CT regulates multiple active conformations of D1-like receptors and may have potential implications for other G protein-coupled receptor classes.     

The prevalence of androstenone anosmia

It has been estimated that approximately 30% of the population is unable to detect the odor of androstenone. These estimates, however, were made using tests and criteria optimized for identifying detection. Such criteria favor Type II over Type I errors--that is, they are excellent at identifying true detectors at the cost of erroneously labeling some detectors as non-detectors. Because these criteria were used to identify non-detectors, it is possible that the rate of non-detection may have been overestimated. To test this we screened 55 subjects for non-detection employing previously used methods. This screen yielded nine putative non-detectors, a 16.3% putative non-detection rate. We then retested these putative non-detectors using a forced choice (yes-no) paradigm to obtain a precise measure of their sensitivity. We found that this group of putative non-detectors was significantly above chance at detecting androstenone (P < 0.001), despite very low self-confidence in their performance. Based on the results of the signal detection analysis in this sample, we estimate the rate of actual androstenone non-detection in young healthy adults is between 1.8 and 5.96%, which is significantly lower than previously estimated. This finding is significant considering the implications of specific anosmias on the understanding of odor discrimination.     

Mapping of QTLs prolonging the latent period of Puccinia triticina infection in wheat

Slow rusting is considered a crucial component of durable resistance to wheat leaf rust caused by Puccinia triticina and is often expressed in the form of a prolonged latent period. Selection for a longer latent period is considered an effective approach to developing wheat cultivars with improved durable resistance to leaf rust. A recombinant inbred line (RIL) population derived from CI 13227 (long latent period) × Suwon 92 (short latent period) was phenotyped for latent period in two greenhouse experiments in separate years, and amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers were analyzed in the same population. Among the RILs, the frequency distribution for latent period was continuous, and latent period was highly correlated between years (r=0.94, P<0.0001). A quantitative trait locus (QTL) prolonging the latent period of P. triticina, designated as QLrlp.osu-2DS, explained 42.8% and 54.5% of the phenotypic and genetic variance in the two experiments, respectively. QLrlp.osu-2DS was mapped on the distal region of chromosome 2DS. Two other QTLs for latent period, QLrlp.osu-2B and QLrlp.osu-7BL, were localized on chromosome 2B and the long arm of chromosome 7B, respectively. Multiple regression analysis showed that these three QTLs collectively explained 58.0% and 73.8% of the phenotypic and genetic variance over two experiments, respectively. Fourteen RILs that carried all three alleles for long latent period at three AFLP loci flanking QLrlp.osu-2DS, QLrlp.osu-2B, and QLrlp.osu-7BL had a mean latent period of 12.5 days, whereas 13 RILs without any long-latent-period alleles at the corresponding loci had a mean latent period of 7.4 days. Three SSR markers closely linked to these QTLs have potential to be applied in marker-assisted selection for prolonged latent period in wheat.