Molecular evolution of Adh and LEAFY and the phylogenetic utility of their introns in Pyrus (Rosaceae)

<p>Abstract</p> <p>Background</p> <p>The genus <it>Pyrus </it>belongs to the tribe Pyreae (the former subfamily Maloideae) of the family Rosaceae, and includes one of the most important commercial fruit crops, pear. The phylogeny of <it>Pyrus </it>has not been definitively reconstructed. In our previous efforts, the internal transcribed spacer region (ITS) revealed a poorly resolved phylogeny due to non-concerted evolution of nrDNA arrays. Therefore, introns of low copy nuclear genes (LCNG) are explored here for improved resolution. However, paralogs and lineage sorting are still two challenges for applying LCNGs in phylogenetic studies, and at least two independent nuclear loci should be compared. In this work the second intron of <it>LEAFY </it>and the alcohol dehydrogenase gene (<it>Adh</it>) were selected to investigate their molecular evolution and phylogenetic utility.</p> <p>Results</p> <p>DNA sequence analyses revealed a complex ortholog and paralog structure of <it>Adh </it>genes in <it>Pyrus </it>and <it>Malus</it>, the pears and apples. Comparisons between sequences from RT-PCR and genomic PCR indicate that some <it>Adh </it>homologs are putatively nonfunctional. A partial region of <it>Adh1 </it>was sequenced for 18 <it>Pyrus </it>species and three subparalogs representing <it>Adh1-1 </it>were identified. These led to poorly resolved phylogenies due to low sequence divergence and the inclusion of putative recombinants. For the second intron of <it>LEAFY</it>, multiple inparalogs were discovered for both <it>LFY1int2 </it>and <it>LFY2int2</it>. <it>LFY1int2 </it>is inadequate for phylogenetic analysis due to lineage sorting of two inparalogs. <it>LFY2int2-N</it>, however, showed a relatively high sequence divergence and led to the best-resolved phylogeny. This study documents the coexistence of outparalogs and inparalogs, and lineage sorting of these paralogs and orthologous copies. It reveals putative recombinants that can lead to incorrect phylogenetic inferences, and presents an improved phylogenetic resolution of <it>Pyrus </it>using <it>LFY2int2-N</it>.</p> <p>Conclusions</p> <p>Our study represents the first phylogenetic analyses based on LCNGs in <it>Pyrus</it>. Ancient and recent duplications lead to a complex structure of <it>Adh </it>outparalogs and inparalogs in <it>Pyrus </it>and <it>Malus</it>, resulting in neofunctionalization, nonfunctionalization and possible subfunctionalization. Among all investigated orthologs, <it>LFY2int2-N </it>is the best nuclear marker for phylogenetic reconstruction of <it>Pyrus </it>due to suitable sequence divergence and the absence of lineage sorting.</p

The endocardium - Its possible role in myocardial function

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Effect of 1-phenylephrine on rat papillary muscle: influence of ageing

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Modification of excitation-contraction coupling in cat ventricular myocardium following endocardial damage

Damage to endocardial endothelium (denudation of the superficial tissue) by brief exposure to a 100-μL bolus of detergent (Triton X-100, 1% by volume stock) decreased the twitch force of papillary muscle (and trabeculae) by ~30% to a new but steady level without changes in resting tension. The decline in twitch force was evident immediately after the addition of Triton. Modification of the action potential measured from the contracting tissue appeared only later, when the change in contraction was already well established (i.e., after ~2 min). Action potential shortened in duration at 50% repolarization by ~100 ms and increased in plateau amplitude, although the latter increase was not always observed. A similar treatment procedure applied to strips of ventricular wall with the endocardium exposed to the superfusion solution resulted in a substantial decrease in action potential duration (~110 ms). In contrast, treatment of strips of epicardial layers of ventricular walls (with epicardial side facing the superfusion solution) did not produce a similar result. In β-stimulated (1 μM isoproterenol) and partially depolarized preparations (with 20 mM KCl), with intact endocardium, electrically evoked contractions were followed by aftercontractions, which were suppressed following Triton treatment. Action potentials in a depolarizing medium also shortened in duration (~50 ms), although following a delay (2-3 min). The decay to steady state of postextrasystolic potentiated beat was slower after endocardial damage than under control conditions. This suggested an increased Ca2+ recirculation through the sarcoplasmic reticulum between two consecutive beats (35% before Triton vs. 45% after Triton). Finally, in a medium containing 3 μM ryanodine, Triton treatment of the endocardial endothelium failed to induce any effect on either twitch force or action potential. Prolonged exposure to Triton X-100 (by a slow flow or high concentration) induced only deteriorating effects leading to substantial rise in the resting tension and generation of contractures and abbreviated action potentials with depressed plateau. These observations are consistent with the hypothesis that a modification in the sarcoplasmic reticulum function may, at least in part, be responsible for the observed changes in contractile function of the myocardium following endocardial damage with Triton treatment.link_to_subscribed_fulltex

Changes in prejunctional potency of B-HT 933 during aging in the rat vas deferens

1. Age-related changes in prejunctional α2-adrenoceptors were examined in the rat vas deferens using pharmacological techniques. 2. B-HT 933 (1x10-8-1x10-6 mol/L) caused a concentration-dependent inhibition of isometric contractions (tetrodotoxin-sensitive) induced by stimulation with single field-stimulus pulses, in both the epididymal and prostatic regions of rat vas deferens. The concentration-response curve to B-HT 933 was shifted to the right with age in the prostatic regions of the vas deferens. 3. In high concentrations (10-6-3x10-4 mol/L), B-HT 933 caused concentration-dependent enhancement of the contractile response to stimulation and evoked spontaneous contractile activity. No significant difference in this postjunctional activity occurred with age in either the prostatic or epididymal regions of the vas deferens. 4. Schild analysis revealed no significant differences in pA2 values for the antagonisms of the prejunctional inhibitory effect of B-HT 933 by rauwolscine in either the prostatic or epididymal regions of vas deferens between young and old rats. 5. These results could be interpreted as a decrease in α2-adrenoceptor number with age. The more marked decrease in the prejunctional inhibitory potency of B-HT 933 in prostatic regions of vas deferens with aging may be due to a smaller receptor reserve in this region of the vas deferens.link_to_subscribed_fulltex

Role of the endocardium in excitation - contraction coupling in isolated cat papillary muscle

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