Brown algae (Phaeophyceae) are complex photosynthetic organisms with a very different evolutionary history to green plants, to which they are only distantly related(1). These seaweeds are the dominant species in rocky coastal ecosystems and they exhibit many interesting adaptations to these, often harsh, environments. Brown algae are also one of only a small number of eukaryotic lineages that have evolved complex multicellularity (Fig. 1). We report the 214 million base pair (Mbp) genome sequence of the filamentous seaweed Ectocarpus siliculosus (Dillwyn) Lyngbye, a model organism for brown algae(2-5), closely related to the kelps(6,7) (Fig. 1). Genome features such as the presence of an extended set of light-harvesting and pigment biosynthesis genes and new metabolic processes such as halide metabolism help explain the ability of this organism to cope with the highly variable tidal environment. The evolution of multicellularity in this lineage is correlated with the presence of a rich array of signal transduction genes. Of particular interest is the presence of a family of receptor kinases, as the independent evolution of related molecules has been linked with the emergence of multicellularity in both the animal and green plant lineages. The Ectocarpus genome sequence represents an important step towards developing this organism as a model species, providing the possibility to combine genomic and genetic(2) approaches to explore these and other(4,5) aspects of brown algal biology further

Members and prospective members of the family Phycodnaviridae are large icosahedral, dsDNA (180 to 560 kb) viruses that infect eukaryotic algae. The genomes of two phycodnaviruses have been sequenced: the 331 kb genome of Paramecium bursaria chlorella virus (PBCV-1) and more recently, the 336 kb genome of the Ectocarpus siliculosus virus (EsV-1). EsV-1 has approximately 231 protein-encoding genes whereas, the slightly smaller PBCV-1 genome has 11 tRNA genes and approximately 375 protein-encoding genes. Surprisingly, the two viruses only have 33 genes in common, of which 17 have no counterparts in the databases. The low number of homologous genes between the two viruses can probably be attributed to their different life styles. PBCV-1 is a lytic virus that infects a unicellular, endosymbiotic freshwater green alga whereas, EsV-1 is a lysogenic virus that infects a free-living filamentous marine brown alga. Furthermore, accumulating evidence indicates that the phycodnaviruses and their genes are ancient, thus allowing significant differences to have evolved. This review briefly describes some of the biological properties of the phycodnaviruses, focusing on PBCV-1 and EsV-1, and then compares their genomes.

The Ectocarpus siliculosus Virus-1, EsV-1, is the type-species of a genus of Phycodnaviridae, the phaeoviruses, infecting marine filamentous brown algae. The EsV-1 genome of 335,593 bp contains tandem and dispersed repetitive elements in addition to a large number of open reading frames of which 231 are currently counted as genes. Many genes can be assigned to functional groups involved in DNA synthesis, DNA integration, transposition, and polysaccharide metabolism. Furthermore, EsV-1 contains components of a surprisingly complex signal transduction system with six different hybrid histidine protein kinases and four putative serine/threonine protein kinases. Several other genes encode polypeptides with protein-protein interaction domains. However, 50% of the predicted genes have no counterparts in data banks. Only 28 of the 231 identified genes have significant sequence similarities to genes of the Chlorella virus PBCV-1, another phycodnavirus. To our knowledge, the EsV-1 genome is the largest viral DNA sequenced to date.

K ؉ channels operate in the plasma membrane and in membranes of organelles including mitochondria. The mechanisms and topogenic information for their differential synthesis and targeting is unknown. This article describes 2 similar viral K ؉ channels that are differentially sorted; one protein (Kesv) is imported by the Tom complex into the mitochondria, the other (Kcv) to the plasma membrane. By creating chimeras we discovered that mitochondrial sorting of Kesv depends on a hierarchical combination of N-and C-terminal signals. Crucial is the length of the second transmembrane domain; extending its C terminus by >2 hydrophobic amino acids redirects Kesv from the mitochondrial to the plasma membrane. Activity of Kesv in the plasma membrane is detected electrically or by yeast rescue assays only after this shift in sorting. Hence only minor structural alterations in a transmembrane domain are sufficient to switch sorting of a K ؉ channel between the plasma membrane and mitochondria.algal viruses ͉ dual targeting ͉ Kϩ channel sorting ͉ PBCV-1 ͉ Esv-1

Summary Background The precise mapping of multiple antibody epitopes recognized by patients’ sera allows a more detailed and differentiated understanding of immunological diseases. It may lead to the development of novel therapies and diagnostic tools. Objective Mapping soy bean specific epitopes relevant for soy bean allergy patients and persons sensitized to soy bean, and analysis of their IgE/IgG binding spectrum. Methods Identification of epitopes using sera, applying an optimized peptide phage display library followed by next‐generation sequencing, specially designed in silico data analysis and subsequent peptide microarray analysis. Results We were able to identify more than 400 potential epitope motifs in soy bean proteins. More than 60% of them have not yet been described as potential epitopes. Eighty‐three peptides, representing the 42 most frequently found epitope candidates, were validated by microarray analysis using 50 sera from people who have been tested positive in skin prick test (SPT). Of these peptides, 56 were bound by antibodies, 55 by serum IgE, 43 by serum IgG and 30 by both. Person‐specific epitope patterns were found for each individual and protein. Conclusions For individuals with clinical symptoms, epitope resolved analyses reveal a high prevalence of IgE binding to a few soy bean specific epitopes. Evaluation of individual immune profiles of patients with soy bean sensitization allows the identification of peptides that do facilitate studying individual IgE/IgG epitope binding patterns. This enables discrimination of sensitization from disease, such assay test has the potential to replace SPT assays

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The brown alga Ectocarpus siliculosus frequently carries an endogenous virus, E. siliculosus virus (EsV-1), the genome of which is a circular, doublestranded DNA molecule of about 320 kbp. After infection, which occurs in the unicellular spores or gametes, the virus is present latently in all somatic cells of the host. Virus multiplication is restricted to cells of the reproductive organs. It has been an open question whether the latent viral DNA occurs as a free episome or becomes integrated into the host genome. PCR studies showed that viral DNA co-migrates with high molecular mass DNA in pulsed-field gel electrophoresis, which confirms that latent viral DNA is integrated into the host genome.Marine filamentous brown algae of the order Ectocarpales frequently carry endogenous viruses with large doublestranded DNA genomes (Mu$ ller et al., 1998). A well-studied example is Ectocarpus siliculosus virus-1 (EsV-1), the icosahedral capsid of which encloses a circular genome of about 320 kbp (Mu$ ller et al., 1990 ; Lanka et al., 1993). Like other brown-algal viruses, EsV-1 exclusively infects cell wall-free zoospores or gametes. Infected cells develop into mature thalli which can produce pathological symptoms in their sporangia or gametangia. These organs become densely packed with viral particles that are eventually released into the surrounding sea water (Fig. 1 a). It is not unusual, however, for infected algae to appear normal and to produce viable spores (Fig. 1 d ) containing the viral genome ( Fig. 1 e, lane 4). In fact, genetic studies and PCR analyses have shown that the latent viral genome is transmitted vertically through meiosis as a Mendelian trait Bra$ utigam et al., 1995).These earlier reports could not distinguish between an episomal free state of the EsV-1 DNA and integration into the Author for correspondence : Nicolas Delaroque.Fax j49 7531 88 2966. e-mail Nicolas.Delaroque!uni-konstanz.de host genome. We report here the results of experiments that were designed to distinguish between these possibilities. We prepared high molecular mass DNA from zoospores and gametes of infected and uninfected algae by using a modification of the protocol of Liu & Whittier (1994). The following clonal isolates of E. siliculosus were used : strain PAr 10n (Fig. 1 b), a healthy female gametophyte (Mu$ ller, 1979 ;Sengco et al., 1996) ; NZVicZ14 ( Fig. 1 a, c), which is infected by EsV-1 and produces virions as well as zoospores carrying a latent viral genome Sengco et al., 1996) ; and strain Nap R-B1 (Fig. 1 d ), which is a phenotypically normal male gametophyte that is latently infected by EsV-1 and does not produce virions . The cultures of PAr 10n and NZVicZ14 were axenic, Nap R-B1 was unialgal. EsV-1 DNA was prepared from virions released by strain NZVicZ14 as described by Lanka et al. (1993). Culture conditions were as described by Mu$ ller (1991 a, b). Mature algae were stored in the dark at 2 mC overnight. Mass release of reproductive cells within 20 min was induced by rapid transfer into a small volume of f...

BackgroundEctocarpus siliculosus virus-1 (EsV-1) is a lysogenic dsDNA virus belonging to the super family of nucleocytoplasmic large DNA viruses (NCLDV) that infect Ectocarpus siliculosus, a marine filamentous brown alga. Previous studies indicated that the viral genome is integrated into the host DNA. In order to find the integration sites of the viral genome, a genomic library from EsV-1-infected algae was screened using labelled EsV-1 DNA. Several fragments were isolated and some of them were sequenced and analyzed in detail.ResultsAnalysis revealed that the algal genome is split by a copy of viral sequences that have a high identity to EsV-1 DNA sequences. These fragments are interspersed with DNA repeats, pseudogenes and genes coding for products involved in DNA replication, integration and transposition. Some of these gene products are not encoded by EsV-1 but are present in the genome of other members of the NCLDV family. Further analysis suggests that the Ectocarpus algal genome contains traces of the integration of a large dsDNA viral genome; this genome could be the ancestor of the extant NCLDV genomes. Furthermore, several lines of evidence indicate that the EsV-1 genome might have originated in these viral DNA pieces, implying the existence of a complex integration and recombination system. A protein similar to a new class of tyrosine recombinases might be a key enzyme of this system.ConclusionOur results support the hypothesis that some dsDNA viruses are monophyletic and evolved principally through genome reduction. Moreover, we hypothesize that phaeoviruses have probably developed an original replication system.