Effect of Lincocin Treatment on the Greening Process in Bean (Phaseolus vulgaris) Leaves

The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –¹⁴CO₂ fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes.     

Lecithotrophic development and metamorphosis in the Indo-West Pacific brittle star Ophiomastix venosa (Echinodermata: Ophiuroidea)

Summary

The larval development of the ophiocomid ophiuroid Ophiomastix venosais described using SEM. The gastrula transforms into a uniformly ciliated early larva which progressively changes into a lecithotrophic late premetamorphic larva with a continuous bilateral ciliated band. This stage is short-lived and equivalent to a highly reduced ophiopluteus. Comparisons between O. venosa and other ophiuroid species whose development has been investigated suggest that, whatever the developmental mode (lecithotrophic or planktotrophic), a pluteus stage always occurs in ophiuroids with planktonic development. Two metamorphic stages were identified, the late metamorphic larva differing from the early one by the closure of the larval mouth. The appearance of the permanent mouth marks the end of the metamorphosis. The postlarva still possesses remnants of larval features. The transformation of the reduced ophiopluteus into a barrel-shaped metamorphic larva with transverse ciliated bands, a vitellaria larva, is followed. The possible occurrence of a unique type of metamorphic larva in non-brooding ophiuroids is discussed. Verification of this, however, needs further SEM investigations on metamorphic larva from species having “regular” planktotrophic development.     

Novel protein from larval sponge cells,ilborin, is related to energy turnover and calcium binding and is conserved among marine invertebrates

Sponges (phylum Porifera) are early-branching animals, whose outwardly simple body plan is underlain by a complex genetic repertoire. The transition from a mobile larva to an attached filter-feeding organism occurs by metamorphosis, a process accompanied by a radical change of the body plan and cell transdifferentiation. The continuity between larval cells and adult tissues is still obscure. In a previous study, we have produced polyclonal antibodies against the major protein of the flagellated cells covering the larva of the sponge Halisarca dujardini, used them to trace the fate of these cells and shown that the larval flagellated cells transdifferentiate into the choanocytes. In the present work, we identified the sequence of this novel protein, which we named ilborin. A search in the open databases showed that multiple orthologues of the newly identified protein are present in sponges, cnidarians, flatworms, ctenophores and echinoderms, but none of them has been described yet. Ilborin has two conserved domains: triosephosphate isomerase-barrel, which has enzymatic activity against macroergic compounds, and canonical EF-hand, which binds calcium. mRNA of ilborin is expressed in the larval flagellated cells. We suggest that the new protein is involved in the calcium-mediated regulation of energy metabolism, whose activation precedes metamorphosis.     

Mouse centromeric tandem repeats in silico and in situ

The search for all sequences containing centromeric (CEN) minor satellite (MiSat) or pericen-tromeric (periCEN) mouse major satellite (MaSat) was conducted in the whole genome shotgun (WGS) database. The sequences were checked for the presence of the known dispersed repeats using the Censor software. The presence of tandem repeats was tested using Tandem Repeat Finder (TRF). Monotonous MiSat and MaSat arrays and MaSat to MiSat array transitions were detected. Moreover, two other types of contacts were revealed: (1) MiSat transition to fragments of retroelements LINE and IAP (ERV family, intracisternal A-type particles), mainly to ORF2 and 5′-LTR containing elements; (2) MaSat transition to two tandem repeats with monomers 21 bp and 31 bp in size. The presence of the MiSat/IAP transition could be checked experimentally. The common DNA motif among the IAP fragments close to MiSat was isolated. IAP-specific primers were constructed and the fragments obtained in PCR with IAP and MiSat primers compiled the plasmid vector library. Clone n51 with the maximum length of the possible insertion (∼no. 800 bp) was selected from the library. FISH on extended chromatin fibers (fiberFISH) carried out on the n51 clone demonstrated that the main signal definitely belonged to CEN. However, the signals on the chromosome arms were also detected that could be due to the partial homology of n51 to the dispersed repeats. The duplicated fiberFISH with MiSat and n51 allowed to measure the distances between the fragments. The previously obtained MS3 sequence has some homology to IAP and CEN localization. Accordingly, the regular associations of MiSat with IAP retroelements were shown in silico and in situ. Together with the published data, the present findings suggest that retroelements or their fragments may be essential components of the normal centromere of higher eukaryotes.     

High-resolution organization of mouse centromeric and pericentromeric DNA

We studied the organization of mouse satellite 3 and 4 (MS3 and MS4) in comparison with major (MaSat) and minor (MiSat) DNA sequences, located in the centromeric and pericentromeric regions of mouse telocentric chromosomes by fiber-FISH. The centromeric region consists of a small block of MiSat and MS3 followed by a pericentromeric block of MaSat with MS4. Inside the block of the long-range cluster, MaSat repeats intermingle mostly with MS4, while MiSat intermingle with MS3. The distribution of GC-rich satellite DNA fragments is less strict than that of AT-rich fragments; it is possible to find MS3 fragments in the MaSat array and MS4 fragments in the MiSat array. The methylation pattern does not fully correspond to one of the four families of satellite DNA (satDNA). In each satDNA fragment only part of the DNA is methylated. MS3 and MS4 are heavily methylated being GC-rich. Pericentomeric satellite DNA fragments are more methylated than centromeric ones. Among the four families of satDNA MS4 is the most methylated while MiSat is methylated only to a minimal extent. Estimation of the average fragment length and average distance between fragments shows that the range of the probes used does not cover the whole centromeric region. The existence of unknown sequences in the mouse centromere is likely.     

A nuclear matrix protein related to intermediate filaments proteins is a member of the complex binding alphoid DNA in vitro

A complex of three proteins (of 80, 70, 58 kDa-p80, p70, and p58, respectively) with the ability to bind alphoid DNA (alpha-satDNA) was revealed by gel mobility shift assay (GMSA) in human nuclear matrix. The probes of the alpha-satDNA bound in the GMSA with the greatest specificity, but the complex was capable of binding human satellite 3 fragment. According to ion exchange and affinity chromatography, the complex includes two DNA-binding proteins, p70 and p80, and a non-DNA-binding one, p58, which enhances the specificity of binding to the alpha-satDNA. GMSA, SDS-PAGE and immunoblotting showed that the lamins, as well as constitutive centromeric proteins (CENP-A, CENP-B, CENP-C, CENP-G), were not incorporated into the complex. It was demonstrated by immunoprecipitation assay that p70 and, probably p58, share a common antigen determinant with the rod domain of intermediate filaments (IF) proteins. The results obtained indicate that the nuclear matrix contains at least one IF-related protein that is able to bind specifically to alpha-satDNA in vitro and that this protein is distinct from the lamins.     

Characterization of mariner transposon from the genome of Himasthla elongata fluke

A novel DNA-transposon Hemar1 has been identified and characterized in the genome of the flatworm Himasthla elongata. This transposon is a representative of the mariner family, which is widely spread in eukaryotes; it belongs to the capitata subfamily and is highly homologous to the mariner element of the freshwater turbellarian worm Dugesia tigrina. The Hemar1 transposon has been established as a dispersed repeat and accounts for about 0.01% of the H. elongata genome. The identified Hemar1 element is a convenient tool for the further study of the functioning of mobile elements in the H. elongata genome.