Is the initiation of macronuclear DNA synthesis in Euplotes dependent on micronuclear functions?

To determine whether the micronucleus makes essential contributions during asexual reproduction, observations were made on cells of Euplotes octocarinatus from which the micronucleus had been removed with a micropipette. Most cells underwent one postenucleation division, then became arrested in macronuclear G1, slowed down in food uptake, developed macronuclear deformations, and finally died. Such cells could be rescued if a micronucleus was reimplanted before macronuclear deformations had developed. When provided with a new micronucleus, cells initiated macronuclear DNA synthesis about 12-16 h later. The data suggest that the micronucleus is involved in the control of the cell's transition from macronuclear G1 to S, and a model is proposed which postulates that in Euplotes macronuclear DNA synthesis is initiated when a micronucleus-encoded "initiator protein" has accumulated to a critical amount.     

Experimentelle Untersuchungen anEuplotes crassus

Ohne ZusammenfassungMit 2 TextabbildungenDer Deutschen Forschungsgemeinschaft danke ich für die großzügige Unterstützung der Untersuchungen. Dank schulde ich auch Frl.B. Jaumann für sorgfältige Mitarbeit und HerrnH. Bauschert für das Zeichnen der Abbildungsvorlagen.     

Tracing paternal ancestry in mice, using the Y-linked, sex-determining locus, Sry

The molecular evolution of mammalian Y-linked DNA sequences is of special interest because of their unique mode of inheritance: most Y- linked sequences are clonally inherited from father to son. Here we investigate the use of Y-linked sequences for phylogenetic inference. We describe a comparative analysis of a 515-bp region from the male sex- determining locus, Sry, in 22 murine rodents (subfamily Murinae, family Muridae), including representatives from nine species of Mus, and from two additional murine genera--Mastomys and Hylomyscus. Percent sequence divergence was < 0.01% for comparisons between populations within a species and was 0.19%-8.16% for comparisons between species. Our phylogenetic analysis of 12 murine taxa resulted in a single most- parsimonius tree that is highly concordant with phylogenies based on mitochondrial DNA and allozymes. A total evidence tree based on the combined data from Sry, mitochondrial DNA, and allozymes supports (1) the monophyly of the subgenus Mus, (2) its division into a Palearctic group (M. musculus, M. domesticus, M. spicilegus, M. Macedonicus, and M. spretus) and an Oriental group (M. cookii++, M. cervicolor, and M. caroli), and (3) sister-group relationships between M. spicilegus and M. macedonicus and between M. cookii and M. cervicolor. We argue that Y- chromosome DNA sequences represent a valuable new source of characters for phylogenetic inference.      

Le ionophore A23187

The acrosomic status of spermatozoa prepared for IVF has been evaluated by means of immunofluorescence test from Fenichel and Hsi using calcium A 23187 ionophore as inductor of acrosome reaction (AR). The spontaneous AR remains slight, even after 6 hour-incubation in Menezo B2 (6,8+2,7%). The response to ionophore, moderate before (11,2+9%), frankly increases after a 6h-capacitation (28,9+8,3%) in a group of 25 IVF couples (tubal indication, normal semen, positive fertilization). Nevertheless, it remains slight or null in 4 cases of unexplained repeated failure of fertilization. The response to ionophore A 23187 allows to explore the kinetics of capacitation of spermatozoa and their ability to perform AR. Its significance in terms of fecondance remains to be precised.     

The holocentric species Luzula elegans shows interplay between centromere and large‐scale genome organization

In higher plants, the large‐scale structure of monocentric chromosomes consists of distinguishable eu‐ and heterochromatic regions, the proportions and organization of which depend on a species' genome size. To determine whether the same interplay is maintained for holocentric chromosomes, we investigated the distribution of repetitive sequences and epigenetic marks in the woodrush Luzula elegans (3.81 Gbp/1C). Sixty‐one per cent of the L. elegans genome is characterized by highly repetitive DNA, with over 30 distinct sequence families encoding an exceptionally high diversity of satellite repeats. Over 33% of the genome is composed of the Angela clade of Ty1/copia LTR retrotransposons, which are uniformly dispersed along the chromosomes, while the satellite repeats occur as bands whose distribution appears to be biased towards the chromosome termini. No satellite showed an almost chromosome‐wide distribution pattern as expected for a holocentric chromosome and no typical centromere‐associated LTR retrotransposons were found either. No distinguishable large‐scale patterns of eu‐ and heterochromatin‐typical epigenetic marks or early/late DNA replicating domains were found along mitotic chromosomes, although super‐high‐resolution light microscopy revealed distinguishable interspersed units of various chromatin types. Our data suggest a correlation between the centromere and overall genome organization in species with holocentric chromosomes.     

Osteoblast autophagy in glucocorticoid-induced osteoporosis

Administration of glucocorticoids is an effective strategy for treating many inflammatory and autoimmune diseases. However, glucocorticoid treatment can have adverse effects on bone, leading to glucocorticoid-induced osteoporosis (GIO), the most common form of secondary osteoporosis. Although the pathogenesis of GIO has been studied for decades, over the past ten years the autophagy machinery has been implicated as a novel mechanism. Autophagy in osteoblasts, osteocytes, and osteoclasts plays a critical role in the maintenance of bone homeostasis. Herein, we specifically discuss how osteoblast autophagy responds to glucocorticoids and its role in the development of GIO.     

Behavioural and chemical mechanisms behind a Mediterranean ant–ant association

1. Interspecific competition among ants is common, and so is competitive exclusion among dominant ant species. In contrast, specific associations between non‐parasitic ant species are rare, especially in the temperate zones. As an exception, the subordinate ant Camponotus lateralis frequently co‐occurs with the dominant Crematogaster scutellaris but rarely with other dominant ants. 2. This association is one of various associations between Camponotus and Crematogaster species across the world. However, the mechanisms behind these co‐occurences are largely unknown. 3. In the present study, we therefore investigated the association of Ca. lateralis and Cr. scutellaris. We studied the spatial association of the nests, interspecific aggression, both species' cuticular hydrocarbon profiles, and their propensity to follow the other species' pheromone trails. 4. Crematogaster scutellaris usually attacked and displaced the generally submissive Ca. lateralis, but was significantly less aggressive at jointly used trails. Camponotus nests were always in close proximity to Crematogaster nests. 5. The cuticular hydrocarbons of both species consisted of alkanes with chain lengths between C21 and C35. The two species had 25 hydrocarbons in common, including mono‐, di‐, and tetramethyl alkanes. Despite this qualitative similarity, however, the quantitative hydrocarbon composition differed between the two species. 6. Camponotus lateralis followed artificial trails containing trail pheromones of Cr. scutellaris, but the latter did not follow Ca. lateralis trail pheromones. Interspecific trail‐following by Camponotus, but not vice versa, has been observed in another Camponotus–Crematogaster association and may be a more general mechanism that facilitates associations between the two ant genera.     

赭纤虫RNA聚合酶Ⅰ基因片段的分析

赭纤虫被认为是一类进化过程中较为原始的纤毛虫。本研究以储纤虫基因组DNA为模板,利用锚定PCR技术,扩增出RNA聚合酶I第二大亚基基因片段,并对扩增出的基因片段进行了克隆和序列分析。结果表明：由该基因片段导出的氨基酸序列中共有10个半胱氨酸,均由通用密码子UGU、UGC编码,开放读框中不存在由UGA转译为半眈氨酸这一非通用密码的现象。     

Programmed translational frameshifting is likely required for expressions of genes encoding putative nuclear protein kinases of the ciliate Euplotes octocarinatus

Three macronuclear genes encoding putative nuclear protein kinases of the ciliate Euplotes octocarinatus syngen 1 were isolated and sequenced. All three deduced gene products share significant properties with a group of recently identified nuclear serine/threonine protein kinases named Ndr. The three predicted proteins contain the twelve conserved catalytic subdomains of protein kinases and 22 near universally-conserved amino acids residues that are characteristic of serine/threonine protein kinases. In addition, there is an approximately 30 amino acid-peptide insertion between subdomains VII and VIII that contains a potential nuclear localization signal. Sequence analysis suggests that expression of the Eondr2 gene requires a + 1 programmed translational frameshift for its translation. Comparison of the deduced EoNdr2 with other known Ndr protein kinases implies that a + 1 ribosomal frameshift occurs at the motif AAATAA.