The origin and evolution of sex chromosomes, revealed by sequencing of the Silene latifolia female genome.

White campion (Silene latifolia, Caryophyllaceae) was the first vascular plant where sex chromosomes were discovered. This species is a classic model for studies on plant sex chromosomes due to presence of large, clearly distinguishable X and Y chromosomes that originated de novo about 11 million years ago (mya), but lack of genomic resources for this relatively large genome (∼2.8 Gb) remains a significant hurdle.

A High Frequency of Chromosomal Duplications in Unicellular Algae Is Compensated by Translational Regulation.

Although duplications have long been recognized as a fundamental process driving major evolutionary innovations, direct estimates of spontaneous chromosome duplication rates, leading to aneuploid karyotypes, are scarce. Here, from mutation accumulation (MA) experiments, we provide the first estimates of spontaneous chromosome duplication rates in six unicellular eukaryotic species, which range from 1 × 10-4 to 1 × 10-3 per genome per generation. Although this is ∼5 to ∼60 times less frequent than spontaneous point mutations per genome, chromosome duplication events can affect 1-7% of the total genome size.

A CLAVATA3-like Gene Acts as a Gynoecium Suppression Function in White Campion.

How do separate sexes originate and evolve? Plants provide many opportunities to address this question as they have diverse mating systems and separate sexes (dioecy) that evolved many times independently. The classic "two-factor" model for evolution of separate sexes proposes that males and females can evolve from hermaphrodites via the spread of male and female sterility mutations that turn hermaphrodites into females and males, respectively. This widely accepted model was inspired by early genetic work in dioecious white campion (Silene latifolia) that revealed the presence of two sex-determining factors on the Y-chromosome, though the actual genes remained unknown.

Features of the Opportunistic Behaviour of the Marine Bacterium in the Microalga Phycosphere.

Although interactions between microalgae and bacteria are observed in both natural environment and the laboratory, the modalities of coexistence of bacteria inside microalgae phycospheres in laboratory cultures are mostly unknown. Here, we focused on well-controlled cultures of the model green picoalga and the most abundant member of its phycosphere, . The prevalence of in cultures raises questions about how this bacterium maintains itself under laboratory conditions in the microalga culture.

The spontaneous mutation rate of Drosophila pseudoobscura.

The spontaneous mutation rate is a very variable trait that is subject to drift, selection and is sometimes highly plastic. Consequently, its variation between close species, or even between populations from the same species, can be very large. Here, I estimated the spontaneous mutation rate of Drosophila pseudoobscura and Drosophila persimilis crosses to explore the mutation rate variation within the Drosophila genus.

Evolution of Mutation Rate in Astronomically Large Phytoplankton Populations.

Genetic diversity is expected to be proportional to population size, yet, there is a well-known, but unexplained lack of genetic diversity in large populations-the "Lewontin's paradox." Larger populations are expected to evolve lower mutation rates, which may help to explain this paradox. Here, we test this conjecture by measuring the spontaneous mutation rate in a ubiquitous unicellular marine phytoplankton species Emiliania huxleyi (Haptophyta) that has modest genetic diversity despite an astronomically large population size.

The Location of the Pseudoautosomal Boundary in .

Y-chromosomes contain a non-recombining region (NRY), and in many organisms it was shown that the NRY expanded over time. How and why the NRY expands remains unclear. Young sex chromosomes, where NRY expansion occurred recently or is on-going, offer an opportunity to study the causes of this process.

Virus-host coexistence in phytoplankton through the genomic lens.

Virus-microbe interactions in the ocean are commonly described by "boom and bust" dynamics, whereby a numerically dominant microorganism is lysed and replaced by a virus-resistant one. Here, we isolated a microalga strain and its infective dsDNA virus whose dynamics are characterized instead by parallel growth of both the microalga and the virus. Experimental evolution of clonal lines revealed that this viral production originates from the lysis of a minority of virus-susceptible cells, which are regenerated from resistant cells.

Evolution of Codon Usage Bias in Diatoms.

Codon usage bias (CUB)-preferential use of one of the synonymous codons, has been described in a wide range of organisms from bacteria to mammals, but it has not yet been studied in marine phytoplankton. CUB is thought to be caused by weak selection for translational accuracy and efficiency. Weak selection can overpower genetic drift only in species with large effective population sizes, such as that has relatively strong CUB, while organisms with smaller population sizes (e.

Immediate Dosage Compensation Is Triggered by the Deletion of Y-Linked Genes in Silene latifolia.

The loss of functional genes from non-recombining sex-specific chromosomes [1, 2], such as the Y chromosomes in mammals [3] or W chromosomes in birds [4], should result in an imbalance of gene products for sex-linked genes [5]. Different chromosome-wide systems that rebalance gene expression are known to operate in organisms with relatively old sex chromosomes [6]; e.g.

First Estimation of the Spontaneous Mutation Rate in Diatoms.

Mutations are the origin of genetic diversity, and the mutation rate is a fundamental parameter to understand all aspects of molecular evolution. The combination of mutation-accumulation experiments and high-throughput sequencing enabled the estimation of mutation rates in most model organisms, but several major eukaryotic lineages remain unexplored. Here, we report the first estimation of the spontaneous mutation rate in a model unicellular eukaryote from the Stramenopile kingdom, the diatom Phaeodactylum tricornutum (strain RCC2967).

Genome Analyses of the Microalga Picochlorum Provide Insights into the Evolution of Thermotolerance in the Green Lineage.

While the molecular events involved in cell responses to heat stress have been extensively studied, our understanding of the genetic basis of basal thermotolerance, and particularly its evolution within the green lineage, remains limited. Here, we present the 13.3-Mb haploid genome and transcriptomes of a halotolerant and thermotolerant unicellular green alga, Picochlorum costavermella (Trebouxiophyceae) to investigate the evolution of the genomic basis of thermotolerance.

The Mutation Rate and the Age of the Sex Chromosomes in Silene latifolia.

Many aspects of sex chromosome evolution are common to both plants and animals [1], but the process of Y chromosome degeneration, where genes on the Y become non-functional over time, may be much slower in plants due to purifying selection against deleterious mutations in the haploid gametophyte [2, 3]. Testing for differences in Y degeneration between the kingdoms has been hindered by the absence of accurate age estimates for plant sex chromosomes. Here, we used genome resequencing to estimate the spontaneous mutation rate and the age of the sex chromosomes in white campion (Silene latifolia).

A Comparison of Selective Pressures in Plant X-Linked and Autosomal Genes.

Selection is expected to work differently in autosomal and X-linked genes because of their ploidy difference and the exposure of recessive X-linked mutations to haploid selection in males. However, it is not clear whether these expectations apply to recently evolved sex chromosomes, where many genes retain functional X- and Y-linked gametologs. We took advantage of the recently evolved sex chromosomes in the plant and its closely related species to compare the selective pressures between hemizygous and non-hemizygous X-linked genes as well as between X-linked genes and autosomal genes.

Spontaneous Mutation Rate in the Smallest Photosynthetic Eukaryotes.

Mutation is the ultimate source of genetic variation, and knowledge of mutation rates is fundamental for our understanding of all evolutionary processes. High throughput sequencing of mutation accumulation lines has provided genome wide spontaneous mutation rates in a dozen model species, but estimates from nonmodel organisms from much of the diversity of life are very limited. Here, we report mutation rates in four haploid marine bacterial-sized photosynthetic eukaryotic algae; Bathycoccus prasinos, Ostreococcus tauri, Ostreococcus mediterraneus, and Micromonas pusilla.

Marinobacter Dominates the Bacterial Community of the Ostreococcus tauri Phycosphere in Culture.

Microalgal-bacterial interactions are commonly found in marine environments and are well known in diatom cultures maintained in laboratory. These interactions also exert strong effects on bacterial and algal diversity in the oceans. Small green eukaryote algae of the class Mamiellophyceae (Chlorophyta) are ubiquitous and some species, such as Ostreococcus spp.

Fitness Effects of Spontaneous Mutations in Picoeukaryotic Marine Green Algae.

Estimates of the fitness effects of spontaneous mutations are important for understanding the adaptive potential of species. Here, we present the results of mutation accumulation experiments over 265-512 sequential generations in four species of marine unicellular green algae, Ostreococcus tauri RCC4221, Ostreococcus mediterraneus RCC2590, Micromonas pusilla RCC299, and Bathycoccus prasinos RCC1105. Cell division rates, taken as a proxy for fitness, systematically decline over the course of the experiment in O.

Oil removal and effects of spilled oil on active microbial communities in close to salt-saturation brines.

Abiotic and biotic processes associated with the degradation of a light petroleum in brines close to the salt-saturation (~31 %) and the effect of labile organic matter (LOM) supply (casaminoacids/citrate; 0.2 and 0.1 % w/v, respectively) were followed during an incubation of 30 days.

Serum cysteine proteases and their inhibitors in rheumatoid arthritis: relation to disease activity and radiographic progression.

This study aims to investigate the serum levels of cysteine proteases cathepsins B and H and their inhibitors stefin A, stefin B, and cystatin C, as well as traditional inflammatory markers such as C-reactive protein in patients with rheumatoid arthritis and to correlate these markers with scores of disease activity and radiographic progression. Seventy-two patients with rheumatoid arthritis were included from two previously described cohorts of patients with chronic polyarthritis. At inclusion, disease activity was assessed by a 28-joint count, patient global assessment, and serum C-reactive protein.

Cathepsins B, L and cystatin C in cyst fluid of ovarian tumors.

Introduction: In cancer, an extracellular and membrane bound localization of cathepsins contribute to the invasion of tumor cells at the basement membrane.

Methods: This is the first study that explored levels of cathepsins B (CatB), L (CatL) and their inhibitor cystatin C (CysC) in the cystic fluid (CF) of ovarian tumors (n = 110).

Results: CF contained considerable amounts of CatB, CatL and CysC.

MIB-1 immunostaining on cytological samples: a protocol without antigen retrieval.

The aim of the study was to evaluate the effect of fixation procedures on MIB-1 immunostaining on microwave-treated Papanicolaou-stained slides and to establish protocol for MIB-1 immunostaining on cytological samples without microwave pre-treatment. Cytospins for immunostaining and nuclear suspension for DNA measurement were prepared from human breast cancer cell line (MCF-7). Following fixation, the cytospins were either stained by Papanicolaou, stored in methanol or air-dried.

Circadian and concentration profile of cathepsin S in sera from healthy subjects and asthmatic patients.

Cathepsin S (CS) has been proposed to be associated with asthma pathogenesis but its exact role is not established. In order to understand this proposed association our objective was to follow the 24-h concentration pattern of CS in sera from apparently healthy subjects and from steroid-independent and steroid-dependent asthmatics before and after one weeks' treatment with methylprednisolone (MP) and cyclosporin A (CsA), respectively. Blood samples were collected every 4 h over a 24-h period.

Cathepsin B/cystatin C complex levels in sera from patients with lung and colorectal cancer.

A sandwich-type ELISA has been developed for quantification of the complex between the cysteine proteinase cathepsin B (CB) and its reversible tight-binding inhibitor cystatin C (CC) in normal and pathological sera. The assay is based on a combination of catching Ab (3E1), raised against CB, and a horseradish peroxidase-labelled detection Ab (1A2), raised against CC. Only the CB/CC complex is able to evoke a signal in this assay.