Synergistic interaction of three ERECTA-family receptor-like kinases controls Arabidopsis organ growth and flower development by promoting cell proliferation

Growth of plant organs relies on coordinated cell proliferation followed by cell growth, but the nature of the cell-cell signal that specifies organ size remains elusive. The Arabidopsis receptor-like kinase (RLK) ERECTA regulates inflorescence architecture. Our previous study using a dominant-negative fragment of ERECTA revealed the presence of redundancy in the ERECTA-mediated signal transduction pathway. Here, we report that Arabidopsis ERL1 and ERL2, two functional paralogs of ERECTA, play redundant but unique roles in a part of the ERECTA signaling pathway, and that synergistic interaction of three ERECTA-family RLKs define aerial organ size. Although erl1 and erl2 mutations conferred no detectable phenotype, they enhanced erecta defects in a unique manner. Overlapping but distinct roles of ERL1 and ERL2 can be ascribed largely to their intricate expression patterns rather than their functions as receptor kinases. Loss of the entire ERECTA family genes led to striking dwarfism, reduced lateral organ size and abnormal flower development, including defects in petal polar expansion, carpel elongation, and anther and ovule differentiation. These defects are due to severely reduced cell proliferation. Our findings place ERECTA-family RLKs as redundant receptors that link cell proliferation to organ growth and patterning.     

Liquid chromatography-electrospray ionization ion trap mass spectrometry for analysis of mesocarb and its metabolites in human urine

A method is described for the determination of metabolites of mesocarb in human urine by combining gradient liquid chromatography and electrospray ionization (ESI)-ion trap mass spectrometry. Seven metabolites (two isomers of hydroxymesocarb, p-hydroxymesocarb, two isomers of dihydroxymesocarb and two isomers of trihydroxymesocarb) and parent drug were detected in human urine after the administration of a single oral dose 10 mg of mesocarb (Sydnocarb, two tablets of 5 mg). Various extraction techniques (free fraction, enzyme hydrolyses and acid hydrolyses) and their comparison were carried out for investigation of the metabolism of mesocarb. After extraction procedure the residue was dissolved in methanol and injected into the column HPLC (Zorbax SB-C18 (Narrow-Bore 2.1 x 150 mm i.d., 5 microm particles)) with mobile phase (0.2 ml/min) of methanol/0.2 mM ammonium acetate. Conformation of the results and identification of all metabolites are performed by LC-MS and LC-MS/MS. The major metabolites of mesocarb in urine of the human were p-hydroxylated derivative of the phenylcarbamoyl group of the parent drug (p-hydrohymesocarb) and dihydroxylated derivative of mesocarb (two isomers of dihydroxymesocarb). This analytical method for dihydrohymesocarb was very sensitive for discriminating the ingestion of mesocarb longer than the parent drug or other metabolites in human urine. The dihydroxymesocarb was detected in urine until 168-192 h after administration of the drug.     

A survey of unequal crossover systems and their mathematical properties

We present a model of gene duplication by means of unequal crossover (UCO) where the probability of any given pairing between homologous sequences scales as a penalty factor p ^z ≤ 1, with z the number of mismatches due to asymmetric sequence alignment. From this general representation, we derive several limiting case models of UCO, some of which have been treated elsewhere in the literature. One limiting case is random unequal crossover (RUCO), obtained by setting p = 1 (corresponding to equiprobable pairings at each site). Another limiting case scenario (the ‘Krueger-Vogel’ model) proposes an optimal ‘endpoint’ alignment which strongly penalizes both overhang and deviations from endpoint matching positions. For both of these scenarios, we make use of the symmetry properties of the transition operator (together with the more general UCO properties of copy number conservation and equal parent-offspring mean copy number) to derive the stationary distribution of gene copy number generated by UCO. For RUCO, the stationary distribution of genotypes is shown to be a negative binomial, or alternatively, a convolution of geometric distributions on ‘haplotype’ frequencies. A different type of model derived from the general representation only allows recombination without overhang (internal UCO or IntUCO). This process has the special property of converging to a single copy length or a distribution on a pair of copy lengths in the absence of any other evolutionary forces. For UCO systems in general, we also show that selection can readily act on gene copy number in all of the UCO systems we investigate due to the perfect heritability (h ² = 1) imposed by conservation of copy number. Finally, some preliminary work is presented which suggests that the more general models based on misalignment probabilities seem to also converge to stationary distributions, which are most likely functions of parameter value p. An erratum to this article is available at .     

Prevalence of hyperthyroidism after exposure during childhood or adolescence to radioiodines from the chornobyl nuclear accident: dose-response results from the Ukrainian-American Cohort Study

Relatively few data are available on the prevalence of hyperthyroidism (TSH concentrations of <0.3 mIU/liter, with normal or elevated concentrations of free T4) in individuals exposed to radioiodines at low levels. The accident at the Chornobyl (Chernobyl) nuclear plant in Ukraine on April 26, 1986 exposed large numbers of residents to radioactive fallout, principally to iodine-131 ((131)I) (mean and median doses = 0.6 Gy and 0.2 Gy). We investigated the relationship between (131)I and prevalent hyperthyroidism among 11,853 individuals exposed as children or adolescents in Ukraine who underwent an in-depth, standardized thyroid gland screening examination 12-14 years later. Radioactivity measurements taken shortly after the accident were available for all subjects and were used to estimate individual thyroid doses. We identified 76 cases of hyperthyroidism (11 overt, 65 subclinical). Using logistic regression, we tested a variety of continuous risk models and conducted categorical analyses for all subjects combined and for females (53 cases, n = 5,767) and males (23 cases, n = 6,086) separately but found no convincing evidence of a dose-response relationship between (131)I and hyperthyroidism. There was some suggestion of elevated risk among females in an analysis based on a dichotomous dose model with a threshold of 0.5 Gy chosen empirically (OR = 1.86, P = 0.06), but the statistical significance level was reduced (P = 0.13) in a formal analysis with an estimated threshold. In summary, after a thorough exploration of the data, we found no statistically significant dose-response relationship between individual (131)I thyroid doses and prevalent hyperthyroidism.     

Advanced procedures for separation and analysis of low molecular weight inhibitor (NCXIF) of the cardiac sodium-calcium exchanger

A low molecular weight inhibitor (NCX(IF)) of the cardiac Na/Ca exchanger, isolated from the calf ventricle tissue, is capable of regulating the muscle strip's contractility and relaxation without involving the beta-activation pathway. The structural analysis of NCX(IF) requires highly purified preparations that fulfill the demanding requirements for mass spectra and NMR analyses. No such preparation is yet available. To this end, new HPLC procedures were developed by a combination of the reverse phase, normal phase, and HILIC (hydrophilic liquid chromatography) techniques. The specific activity of NCX(IF) is 10(5) times higher in the purified preparations (as compared to the crude extract) showing a 2-5% yield of total inhibitory activity and 20-100 microg content of final material. The purification yield reveals that 1 kg ventricle muscle contains 0.1-0.2 mg NCX(IF), meaning that the tissue concentrations of NCX(IF) may reach 10(-7)-10(-6) M. The diode-array scanning of purified preparations of NCX(IF) shows a homogeneous 3D peak with a maximal absorption at 202 nm. These spectral properties may represent a five-membered ring (e.g., proline, histidine) and/or simple chemical groups (like amine, carbonyl, ester, etc.), but not an aromatic ring or complex conjugates (alkyne, alkene, aldehyde, etc.). NCX(IF) does not respond to phenol/sulfur reagent, suggesting that it lacks reducing (aldo) sugar. NCX(IF) shows a faint response to fluorescamine, meaning that it may contain an amino group (or its derivative). It is believed that a combination of presently developed procedures with LC/MS and LC/MS/MS may provide a useful tool for structural analysis of NCX(IF).     

A STRUCTURED COALESCENT PROCESS FOR SEASONALLY FLUCTUATING POPULATIONS

Many short‐lived organisms pass through several generations during favorable growing seasons, separated by inhospitable periods during which only small hibernating or estivating refugia remain. This induces pronounced seasonal fluctuations in population size and metapopulation structure. The first generations in the growing season will be characterized by small, relatively isolated demes whereas the later generations will experience larger deme sizes with more extensive gene flow. Fluctuations of this sort can induce changes in the amount of genetic variation in early season samples compared to late season samples, a classical example being the observations of seasonal variation in allelism in New England Drosophila populations by P.T. Ives. In this article, we study the properties of a structured coalescent process under seasonal fluctuations using numerical analysis of exact state equations, analytical approximations that rely on a separation of timescales between intrademic versus interdemic processes, and individual‐based simulations. We show that although an increase in genetic variation during each favorable growing season is observed, it is not as pronounced as in the empirical observations. This suggests that some of the temporal patterns of variation seen by Ives may be due to selection against deleterious lethals rather than neutral processes.     

The phylogeny and evolution of deoxyribonuclease II: an enzyme essential for lysosomal DNA degradation

Deoxyribonuclease II (DNase II) is an endonuclease with optimal activity at low pH, localized within the lysosomes of higher eukaryotes. The origin of this enzyme remains in dispute, and its phylogenetic distribution leaves many questions about its subsequent evolutionary history open. Earlier studies have documented its presence in various metazoans, as well as in Dictyostelium, Trichomonas and, anomalously, a single genus of bacteria (Burkholderia). This study makes use of searches of the genomes of various organisms against known DNase II query sequences, in order to determine the likely point of origin of this enzyme among cellular life forms. Its complete absence from any other bacteria makes prokaryotic origin unlikely. Convincing evidence exists for DNase II homologs in Alveolates such as Paramecium, Heterokonts such as diatoms and water molds, and even tentative matches in green algae. Apparent absences include red algae, plants, fungi, and a number of parasitic organisms. Based on this phylogenetic distribution and hypotheses of eukaryotic relationships, the most probable explanation is that DNase II has been subject to multiple losses. The point of origin is debatable, though its presence in Trichomonas and perhaps in other evolutionarily basal "Excavate" protists such as Reclinomonas, strongly support the hypothesis that DNase II arose as a plesiomorphic trait in eukaryotes. It probably evolved together with phagocytosis, specifically to facilitate DNA degradation and bacteriotrophy. The various absences in many eukaryotic lineages are accounted for by loss of phagotrophic function in intracellular parasites, in obligate autotrophs, and in saprophytes.     

Gene structure,transcripts and calciotropic effects of the PTH family of peptides in <Emphasis Type="Italic">Xenopus</Emphasis> and chicken

Background  

Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) belong to a family of endocrine factors that share a highly conserved N-terminal region (amino acids 1-34) and play key roles in calcium homeostasis, bone formation and skeletal development. Recently, PTH-like peptide (PTH-L) was identified in teleost fish raising questions about the evolution of these proteins. Although PTH and PTHrP have been intensively studied in mammals their function in other vertebrates is poorly documented. Amphibians and birds occupy unique phylogenetic positions, the former at the transition of aquatic to terrestrial life and the latter at the transition to homeothermy. Moreover, both organisms have characteristics indicative of a complex system in calcium regulation. This study investigated PTH family evolution in vertebrates with special emphasis on Xenopus and chicken.     

The Origin and Evolution of Vertebrate Glycine Transporters

In the vertebrate central nervous system, glycinergic neurotransmission is regulated by the action of the glycine transporters 1 and 2 (GlyT1 and GlyT2)—members of the solute carrier family 6 (SLC6). Several invertebrate deuterostomes have two paralogous glycine carrier genes, with one gene in the pair having greater sequence identity and higher alignment scores with respect to GlyT1 and the other paralog showing greater similarity to GlyT2. In phylogenetic trees, GlyT2-like sequences from invertebrate deuterostomes form a monophyletic subclade with vertebrate GlyT2, while invertebrate GlyT1-like proteins constitute an outgroup to both the GlyT2-like proteins and to vertebrate GlyT1 sequences. These results are consistent with the hypothesis that vertebrate GlyT1 and GlyT2 are, respectively, derived from GlyT1- and GlyT2-like genes in invertebrate deuterostomes. This implies that the gene duplication which gave rise to these paralogs occurred prior to the origin of vertebrates. GlyT2 subsequently diverged significantly from its invertebrate orthologs (i.e., through the acquisition of a unique N-terminus) as a consequence of functional specialization, being expressed principally in the lower CNS; while GlyT1 has activity in both the lower CNS and several regions of the forebrain.