Calea dalyi (Compositae: Heliantheae), a new species from the Serranía de Santiago,Bolivia

A new species of Compositae, Calea dalyi (of section Meyeria), from eastern Bolivia is described and illustrated. Its closest congener is C. purpurea from westernmost Bahia, Brazil. A key to the members of the C. teucriifolia complex is provided.     

FLORAL INITIATION AND EARLY DEVELOPMENT IN ERIGERON PHILADELPHICUS (ASTERACEAE)

The order of floral initiation and subsequent organogeny of Erigeron philadelphicus L. (Asteraceae: Astereae) was found to deviate from the acropetal pattern generally reported for the Asteraceae. Light micrographs show periclinal divisions in the first, second, and deeper subsurface layers of cells on the flanks of the inflorescence apex as the earliest evidence of floral initiation. Scanning electron microscope micrographs indicate that the disk flowers appear first and arise as small protuberances approximately one-third of the way up the previously and undifferentiated highly convex inflorescence apex. A succession of disk flowers arises acropetally in a complex anthotaxy characterized by about 21 dextrorse and 12–15 sinistrorse parastichies (although this pattern is obscured at the apex). After one to three disk flowers have been initiated in each parastichy, the first ray flower initials can be seen to initiate in sites proximal to the oldest and largest disk flowers. Additional ray flowers then initiate basipetally following the dextrorse parastichies established by the disk flowers. Overall floral initiation on the inflorescence apex proceeds acropetally for the disk flowers and basipetally for the ray flowers until the available space is filled. Floral development adheres to the same plan—proceeding bidirectionally on the inflorescence meristem with the oldest and most complete flowers of both types located on the equator established at initiation.     

New species and combinations in Sabazia (Heliantheae,Galinoginae)

The genusSabazia is expanded to include the genusTricarpha, Calea palmeri, and several newly described taxa,S. tridacoides var.tridacoides and var.latifolia, S. palmeri var.lancifolia, andS. longiradiata. Comparative studies of several morphological features suggest thatSabazia is most clearly related toSelloa andGalinsoga. Karyological data reinforce this observation: inSelloa andGalinsoga x = 8 whereas inSabazia x = 4 andn = 4, 8, 16, or 24. Several species ofCalea are very similar toSabazia in floral features and may be of close phyletic affinity, but most species ofCalea differ conspicuously, suggesting more remote relationships. Other taxa in the Galinsoginae apparently fairly closely allied toSabazia includeOteiza andTridax.

     

Flavonol methyl ethers from Chrysothamnus viscidiflorus

Two new flavonols, 5,7,4′-trihydroxy-3,6,8,3′-tetramethoxyflavone and quercetagetin 3,5,6,3′-tetramethyl ether, were identified in leaves of Chrysothamnus viscidiflorus. Eight known methyl ethers based on kaempferol, quercetin or their 6-hydroxy derivatives were also detected.     

Systematic implicationsofflavonoid patterns in Haplopappus segregates

Complex flavonoid patterns are correlated with primitive woody taxa and high base chromosome numbers among Haplopappus segregates. Variability among flavonoid complements supports the polyphyletic interpretation of the genus.     

Endothelial Transient Receptor Potential Conical Channel (TRPC)-3 Activation Induces Vasogenic Edema Formation in the Rat Piriform Cortex Following Status Epilepticus

Transient receptor potential canonical channel (TRPC) is a nonselective cation channel permeable to Ca²⁺, which express in many cell types, including neurons. However the alterations in TRPC receptor expressions in response to status epilepticus (SE) have not been explored. Therefore, the present study was designated to elucidate the roles of TRPC3 in neuronal death and vasogenic edema within the rat piriform cortex (PC) following SE. In non-SE animals, TRPC3 immunoreactivity was abundantly detected in the PC. Following SE, TRPC3 immunoreactivity was increased in neurons. Furthermore, TRPC3 expression was detected in endothelial cells that did not contain it in non-SE animals. Loss of SMI-71 (a blood–brain barrier antigen) immunoreactivity was also observed in TRPC3 positive endothelial cells. In addition, FJB positive neurons and vasogenic edema were noticeably detected in the PC. To directly determine whether TRPC3 activation is correlated to SE-induced vasogenic edema formation and neuronal damages in the PC, the effect of Pyr-3 (a TRPC3 antagonist) on SE-induced insults were investigated. Pyr-3 infusion effectively attenuated vasogenic edema in the PC as compared to the vehicle. Therefore, our findings indicate that TRPC3 activation/overexpression induced by SE may involve BBB disruption and neuronal damages in the rat PC following SE. Therefore, the present study was TRPC3 may play an important role in SE-induced vasogenic edema formation through BBB disruptions in the rat PC.     

P-glycoprotein catalytic mechanism: studies of the ADP-vanadate inhibited state

Kinetics of inhibition of ATPase activity of pure mouse Mdr3 P-glycoprotein upon incubation with MgADP and vanadate were studied along with the trapping of [14C]ADP in presence of vanadate. The presence of verapamil strongly magnified both effects. Inhibition of ATPase was also increased by several other drugs known to bind to drug-binding sites. Inhibition by ADP-vanadate was slow and depended cooperatively on nucleotide binding. Stoichiometry of [14C]ADP trapping by vanadate was 1 mol/mol P-glycoprotein at full inhibition. Catalytic site mutants prevented [14C]ADP trapping, whereas interdomain signal communication mutants reduced it in approximate correlation with their effects upon drug stimulation of ATPase. In explanation of the results, we propose that a "closed conformation" involving dimerization and interdigitation of the two nucleotide-binding domains is necessary to allow inhibition by ADP-vanadate. The results suggest that such a conformation occurs naturally during ATP hydrolysis. It is proposed that in order for the catalytic transition state to form, the two nucleotide-binding domains dimerize to form an integrated single entity containing two bound ATP with just one of the two ATP being hydrolyzed per dimerization event.     

Conserved walker A Ser residues in the catalytic sites of P-glycoprotein are critical for catalysis and involved primarily at the transition state step

P-glycoprotein mutants S430A/T and S1073A/T, affecting conserved Walker A Ser residues, were characterized to elucidate molecular roles of the Ser and functioning of the two P-glycoprotein catalytic sites. Results showed the Ser-OH is critical for MgATPase activity and formation of the normal transition state, although not for initial MgATP binding. Mutation to Ala in either catalytic site abolished MgATPase and transition state formation in both sites, whereas Thr mutants had similar MgATPase to wild-type. Trapping of 1 mol of MgADP/mol of P-glycoprotein by vanadate, shown here with pure protein, yielded full inhibition of ATPase. Thus, congruent with previous work, both sites must be intact and must interact for catalysis. Equivalent mutations (Ala or Thr) in the two catalytic sites had identical effects on a wide range of activities, emphasizing that the two catalytic sites function symmetrically. The role of the Ser-OH is to coordinate Mg(2+) in MgATP, but only at the stage of the transition state are its effects tangible. Initial substrate binding is apparently to an "open" catalytic site conformation, where the Ser-OH is dispensable. This changes to a "closed" conformation required to attain the transition state, in which the Ser-OH is a critical ligand. Formation of the latter conformation requires both sites; both sites may provide direct ligands to the transition state.     

Horizontal Transfer of Archaeal Genes into the Deinococcaceae: Detection by Molecular and Computer-Based Approaches

Members of the Deinococcaceae (e.g., Thermus, Meiothermus, Deinococcus) contain A/V-ATPases typically found in Archaea or Eukaryotes which were probably acquired by horizontal gene transfer. Two methods were used to quantify the extent to which archaeal or eukaryotic genes have been acquired by this lineage. Screening of a Meiothermus ruber library with probes made against Thermoplasma acidophilum DNA yielded a number of clones which hybridized more strongly than background. One of these contained the prolyl tRNA synthetase (RS) gene. Phylogenetic analysis shows the M. ruber and D. radiodurans prolyl RS to be more closely related to archaeal and eukaryal forms of this gene than to the typical bacterial type. Using a bioinformatics approach, putative open reading frames (ORFs) from the prerelease version of the D. radiodurans genome were screened for genes more closely related to archaeal or eukaryotic genes. Putative ORFs were searched against representative genomes from each of the three domains using automated BLAST. ORFs showing the highest matches against archaeal and eukaryotic genes were collected and ranked. Among the top-ranked hits were the A/V-ATPase catalytic and noncatalytic subunits and the prolyl RS genes. Using phylogenetic methods, ORFs were analyzed and trees assessed for evidence of horizontal gene transfer. Of the 45 genes examined, 20 showed topologies in which D. radiodurans homologues clearly group with eukaryotic or archaeal homologues, and 17 additional trees were found to show probable evidence of horizontal gene transfer. Compared to the total number of ORFs in the genome, those that can be identified as having been acquired from Archaea or Eukaryotes are relatively few (approximately 1%), suggesting that interdomain transfer is rare.     

Phylogenetic insights into New World Cyperus (Cyperaceae) using nuclear ITS sequences

We analyzed nuclear ITS sequences of 95 samples representing 85 taxa of Cyperus sensu lato under maximum likelihood and Bayesian frameworks. This work is exploratory in nature with the objectives of gaining insight into relationships among New World Cyperus and targeting problematic clades for future research. In our resulting phylogenetic hypothesis, the genera Cyperus, Kyllinga, Oxycaryum, Pycreus, and Queenslandiella were intermixed, confirming the paraphyletic nature of Cyperus as reported by other researchers. We recovered a strongly-supported clade whose members possess C₄ photosynthesis. The C₃/C₄ split has also been previously reported based on research employing different methods of phylogenetic estimation and different molecular markers. We provide preliminary evidence that Cyperus sections Haspani, Laxiglumi, Strigosi, Thunbergiani, and Umbellati are not monophyletic. Cyperus subgenus Diclidium, which is characterized by a unique mode of spikelet shattering, is monophyletic and highly derived in our analysis, but additional taxa are needed for a more robust assessment. We discuss hypothesized relationships and taxonomic implications for several other species and species complexes.