Mirror‐symmetric microtubule assembly and cell interactions drive lumen formation in the zebrafish neural rod

By analysing the cellular and subcellular events that occur in the centre of the developing zebrafish neural rod, we have uncovered a novel mechanism of cell polarisation during lumen formation. Cells from each side of the neural rod interdigitate across the tissue midline. This is necessary for localisation of apical junctional proteins to the region where cells intersect the tissue midline. Cells assemble a mirror‐symmetric microtubule cytoskeleton around the tissue midline, which is necessary for the trafficking of proteins required for normal lumen formation, such as partitioning defective 3 and Rab11a to this point. This occurs in advance and is independent of the midline cell division that has been shown to have a powerful role in lumen organisation. To our knowledge, this is the first example of the initiation of apical polarisation part way along the length of a cell, rather than at a cell extremity. Although the midline division is not necessary for apical polarisation, it confers a morphogenetic advantage by efficiently eliminating cellular processes that would otherwise bridge the developing lumen.     

The gene for mitochondrial ribosomal protein S14 has been transferred to the nucleus in Arabidopsis thaliana

The transfer of genetic information from the mitochondrion to the nucleus is thought to be still underway in higher plants. The mitochondrial genome of Arabidopsis thaliana contains only one rps14 pseudogene. In this paper we show that the functional gene encoding mitochondrial ribosomal protein S14 has been translocated to the nucleus. This gene transfer is a recent evolutionary event, which occurred within Cruciferae, probably after the divergence of Arabidopsis and Brassica napus. A 5′ extension of the rps14 reading frame encodes a presequence which, in?vitro, targets the polypeptide to isolated mitochondria and is cleaved off during or after import. No intron was found at the junction of the targeting presequence with the mitochondrially derived sequence, which are directly connected. By contrast, a 90-bp intron, which is removed by splicing to give a mature poly(A)⁺mRNA of 0.9 kb, is located in the 3′ non-coding region. To our knowledge, this is the first report of an intron in such a position in a functional transferred gene in higher plants, and suggests that exon shuffling may have been involved in the acquisition of elements necessary for expression in the nucleus. Putative roles of this intron in polyadenylation and enhancement of gene expression are discussed.     

The -308 polymorphism in the promoter region of the tumor necrosis factor-alpha (TNF-alpha) gene and ex vivo lipopolysaccharide-induced TNF-alpha expression in patients with aggressive periodontitis and/or type 1 diabetes mellitus

Several single-nucleotide polymorphisms (SNPs) have been identified in the TNF-alpha gene promoter. The transition G-->A at position -308 generates the TNF-alpha1 (G/G) and TNF-alpha2 (G/A or A/A) alleles, where the polymorphic TNF-alpha2 allele is associated with a high, in vitro TNF-alpha expression and an increased susceptibility to diverse illnesses. Here we study the association of the -308 TNF-alpha SNP with the susceptibility for developing aggressive periodontitis (AP), AP combined with type 1 diabetes mellitus (DM) and DM. We also explore the TNF-alpha capability expression and the presence of the -308 polymorphism. For this purpose we recruited 27 individuals with AP (AP+ group), 27 individuals with AP combined with DM (AP+/DM+ group), and 27 individuals with DM without signs of periodontitis upon clinical examination (DM+ group). The control group was comprised of 30 subjects. Genotyping for TNF-alpha promoter was performed by PCR-RFLP analysis. For TNF-alpha expression we used a blood culture system.     

The Active and the Inactive Form of the hAT1 Receptor Have an Identical Ligand-Binding Environment: An MPA Study on a Constitutively Active Angiotensin II Receptor Mutant

Several models of activation mechanisms were proposed for G protein-coupled receptors (GPCRs), yet no direct methods exist for their elucidation. The availability of constitutively active mutants has given an opportunity to study active receptor conformations within acceptable limits using models such as the angiotensin II type 1 (AT₁)¹ receptor mutant N111G-hAT₁ which displays an important constitutive activity. Recently, by using methionine proximity assay, we showed for the hAT₁ receptor that TMD III, VI, and VII form the ligand-binding pocket of the C-terminal amino acid of an antagonistic AngII analogue. In the present contribution, we investigated whether the same residues would also constitute the ligand-binding contacts in constitutively activated mutant (CAM) receptors. For this purpose, the same Met mutagenesis strategy was carried out on the N111G double mutants. Analysis of 43 receptors mutants in the N111G-hAT₁ series, photolabeled and CNBr digested, showed that there were only subtle structural changes between the wt-receptor and its constitutively active form.     

Manipulation of light and CO2 environments of the primary leaves of bean (Phaseolus vulgaris L.) affects photosynthesis in both the primary and the first trifoliate leaves: involvement of systemic regulation.

Possible involvement of systemic regulation of the photosynthetic properties of young leaves by the local environments and/or photosynthate production of the mature leaves were examined using Phaseolus vulgaris plants. When primary leaves (PLs) were treated with air containing 150 microL CO2 L(-1) with the other plant parts in ambient air at a photosynthetic photon flux density (PPFD) of 300 micromol photon m(-2) s(-1), decreases in the photosynthetic rate measured at 360 microL CO2 L(-1) and a PPFD of 300 micromol photon m(-2) s(-1) (A360) were markedly retarded in both PLs and the first trifoliate leaves (TLs) as compared to plants treated with 400 microL CO2 L(-1). Conversely, when PLs were treated with 1000 microL CO2 L(-1), decreases in A360 were accelerated in both PLs and TLs. Shading of PLs accelerated the decrease in PL A360, and delayed the decrease in TLs. In the CO2 treatments, changes in A360 in TLs were mainly attributed to the changes in ribulose bisphosphate (RuBP) carboxylation rate, while the shading of PLs caused increases in both the RuBP carboxylation and regeneration rates in TLs. The ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) activity on chlorophyll basis, an indicator of sun/shade acclimation, differed both among PLs and among TLs in accordance with the redox state of photosystem II (PSII) in PLs. Although carbohydrate contents of TLs were not affected by any manipulation of PLs, changes in the photosynthetic capacities of TLs acted to compensate for changes in PL photosynthesis. These results clearly indicate that the CO2 and shade treatments of PLs not only affect photosynthetic properties of the PLs themselves, but also systemically affected the photosynthetic properties of TLs. Possible roles of the redox state and photosynthate concentration in PLs in regulation of photosynthesis in PLs and TLs are discussed.