Plastid DNA sequencing and nuclear SNP genotyping help resolve the puzzle of central American Platanus

Background and Aims

Recent research on the history of Platanus reveals that hybridization phenomena occurred in the central American species. This study has two goals: to help resolve the evolutive puzzle of central American Platanus, and to test the potential of real-time polymerase chain reaction (PCR) for detecting ancient hybridization.

Methods

Sequencing of a uniparental plastid DNA marker [psbA-trnH^(GUG) intergenic spacer] and qualitative and quantitative single nucleotide polymorphism (SNP) genotyping of biparental nuclear ribosomal DNA (nrDNA) markers [LEAFY intron 2 (LFY-i2) and internal transcribed spacer 2 (ITS2)] were used.

Key Results

Based on the SNP genotyping results, several Platanus accessions show the presence of hybridization/introgression, including some accessions of P. rzedowskii and of P. mexicana var. interior and one of P. mexicana var. mexicana from Oaxaca (= P. oaxacana). Based on haplotype analyses of the psbA-trnH spacer, five haplotypes were detected. The most common of these is present in taxa belonging to P. orientalis, P. racemosa sensu lato, some accessions of P. occidentalis sensu stricto (s.s.) from Texas, P. occidentalis var. palmeri, P. mexicana s.s. and P. rzedowskii. This is highly relevant to genetic relationships with the haplotypes present in P. occidentalis s.s. and P. mexicana var. interior.

Conclusions

Hybridization and introgression events between lineages ancestral to modern central and eastern North American Platanus species occurred. Plastid haplotypes and qualitative and quantitative SNP genotyping provide information critical for understanding the complex history of Mexican Platanus. Compared with the usual molecular techniques of sub-cloning, sequencing and genotyping, real-time PCR assay is a quick and sensitive technique for analysing complex evolutionary patterns.     

GABAA Receptors of Cerebellar Granule Cells in Culture: Interaction with Benzodiazepines

GABA_A receptor mediated inhibition plays an important role in modulating the input/output dynamics of cerebellum. A characteristic of cerebellar GABA_A receptors is the presence in cerebellar granule cells of subunits such as α6 and δ which give insensitivity to classical benzodiazepines. In fact, cerebellar GABA_A receptors have generally been considered a poor model for testing drugs which potentially are active at the benzodiazepine site. In this overview we show how rat cerebellar granule cells in culture may be a useful model for studying new benzodiazepine site agonists. This is based on the pharmacological separation of diazepam-sensitive α1 β2/3 γ2 receptors from those which are diazepam-insensitive and contain the α6 subunit. This is achieved by utilizing furosemide/Zn²⁺ which block α6 containing and incomplete receptors.     

The 2-arachidonoylglycerol effect on myosin light chain phosphorylation in human platelets

In human platelets the endocannabinoid 2-arachidonoylglycerol (2-AG) stimulates some important pathways leading to thromboxane B₂ formation, calcium intracellular elevation, ATP secretion and actin polymerisation. The aim of the present study was to examine the 2-AG effect on myosin light chain (MLC) phosphorylation and to investigate the mechanisms involved. We demonstrated that 2-AG induced a rapid MLC phosphorylation, stimulating both the RhoA kinase (ROCK) and MLC kinase (MLCK) in a dose and time-dependent manner. In addition MLC phosphorylation was strengthened through the MLC phosphatase inhibition. MLC phosphatase inhibition was accomplished through the RhoA/ROCK and protein kinase C mediated phosphorylation of MLC phosphatase inhibiting subunits MYPT1 and CPI-17. The presence of CB1 receptor in human platelets and the involvement of CB1 receptor in MLC phosphorylation and MLC phosphatase inhibition was shown.     

Contribution of genetic and epigenetic mechanisms to Wnt pathway activity in prevalent skeletal disorders

We reported previously that the expression of Wnt-related genes is lower in osteoporotic hip fractures than in osteoarthritis. We aimed to confirm those results by analyzing β-catenin levels and explored potential genetic and epigenetic mechanisms involved.     

A fossil stemmiulid millipede (Diplopoda: Stemmiulida) from the Miocene amber of Simojovel,Chiapas, México

A fossil millipede representative of the order Stemmiulida is described on the basis of a well-preserved adult female trapped in amber from the Miocene of Simojovel, Chiapas, south-eastern México. The fossil specimen is named as Parastemmiulus elektron, a new genus and species. As observed in extant stemmiulids, this fossil shows a reduced number of ocelli, the distal larger than the proximal, as well as a total of 46 trunk segments including 2 apodous segments in front of the telson. The head of this ancient stemmiulid has three ocelli and a Tömösváry organ, characteristics not reported before in Stemmiulida, requiring the diagnosis of the order to be emended.http://zoobank.org/urn:lsid:zoobank.org:pub:361400A8-37D4-421F-B4FD-A0AE63BE538C     

CXCL12-Mediated Murine Neural Progenitor Cell Movement Requires PI3Kβ Activation

The migratory route of neural progenitor/precursor cells (NPC) has a central role in central nervous system development. Although the role of the chemokine CXCL12 in NPC migration has been described, the intracellular signaling cascade involved remains largely unclear. Here we studied the molecular mechanisms that promote murine NPC migration in response to CXCL12, in vitro and ex vivo. Migration was highly dependent on signaling by the CXCL12 receptor, CXCR4. Although the JAK/STAT pathway was activated following CXCL12 stimulation of NPC, JAK activity was not necessary for NPC migration in vitro. Whereas CXCL12 activated the PI3K catalytic subunits p110α and p110β in NPC, only p110β participated in CXCL12-mediated NPC migration. Ex vivo experiments using organotypic slice cultures showed that p110β blockade impaired NPC exit from the medial ganglionic eminence. In vivo experiments using in utero electroporation nonetheless showed that p110β is dispensable for radial migration of pyramidal neurons. We conclude that PI3K p110β is activated in NPC in response to CXCL12, and its activity is necessary for immature interneuron migration to the cerebral cortex.     

3 Origins and evolution of the translation machinery

The protein synthesis machinery largely evolved prior to the last common ancestor and hence its study can provide insight to early events in the origin of life, including the transition from the hypothetical RNA world to living systems as we know them. By utilizing information from primary sequences, atomic resolution structures, and functional properties of the various components, it is possible to identify timing relationships (Hsiao et al., 2009; Fox, 2010). Taken together, these timing events are used to develop a preliminary time line for major evolutionary events leading to the modern protein synthesis machinery. It has been argued that a key initial event was the hybridization of two or more RNAs that created the peptidyl transferase center, (PTC), of the ribosome (Agmon et al. 2005). The PTC, left side of figure, contains a characteristic cavity/pore that serves as the entrance to the exit tunnel and is thought to be essential to the catalysis (Fox et al., 2012). This cavity is distinct from typical RNA pores (right side of figure) in that the nitrogenous bases face towards the lumen of the pore and thus are available for hydrogen bonding interactions. In typical RNA pores, the bases carefully avoid the lumen region. In support of Agmon et al. 2005), it is argued that this key difference reflects the fact the pore was created by an early hybridization event rather than normal RNA folding.