Insights into the Evolution of Multicellularity from the Sea Lettuce Genome.

We report here the 98.5 Mbp haploid genome (12,924 protein coding genes) of Ulva mutabilis, a ubiquitous and iconic representative of the Ulvophyceae or green seaweeds. Ulva's rapid and abundant growth makes it a key contributor to coastal biogeochemical cycles; its role in marine sulfur cycles is particularly important because it produces high levels of dimethylsulfoniopropionate (DMSP), the main precursor of volatile dimethyl sulfide (DMS).

A new flagellated dispersion stage in , a pathogen of .

The blastocladialean fungus Boussiba, Zarka and James is a devastating pathogen of the commercially valuable green microalga , a natural source of the carotenoid pigment astaxanthin. First identified in commercial cultivation facilities, is hypothesised to have a complex life cycle that switches between a vegetative and a resting phase depending on favourable or unfavourable growth conditions. Rather unusually for blastocladialean fungi, was described as lacking flagellated zoospores and only propagating via aplanosporic amoeboid cells.

Infection of the brown alga Ectocarpus siliculosus by the oomycete Eurychasma dicksonii induces oxidative stress and halogen metabolism.

Pathogens are increasingly being recognized as key evolutionary and ecological drivers in marine ecosystems. Defence mechanisms of seaweeds, however, have mostly been investigated by mimicking infection using elicitors. We have established an experimental pathosystem between the genome brown model seaweed Ectocarpus siliculosus and the oomycete Eurychasma dicksonii as a powerful new tool to investigate algal responses to infection.

Sexual dimorphism and the evolution of sex-biased gene expression in the brown alga ectocarpus.

Males and females often have marked phenotypic differences, and the expression of these dissimilarities invariably involves sex differences in gene expression. Sex-biased gene expression has been well characterized in animal species, where a high proportion of the genome may be differentially regulated in males and females during development. Male-biased genes tend to evolve more rapidly than female-biased genes, implying differences in the strength of the selective forces acting on the two sexes.

Attachment, penetration and early host defense mechanisms during the infection of filamentous brown algae by Eurychasma dicksonii.

Eurychasma dicksonii is one of the most common and widespread marine pathogens and attacks a broad spectrum of more than 45 brown algal species. The present study focuses on the mechanism used by the pathogen to attach on the host cell wall and force its way into algal cells. Ultrastructural examination revealed a needle-like structure which develops within the attached spore and extends along its main axis.

Filamentous brown algae infected by the marine, holocarpic oomycete Eurychasma dicksonii: first results on the organization and the role of cytoskeleton in both host and parasite.

The important role of the cytoskeletal scaffold is increasingly recognized in host-pathogen interactions. The cytoskeleton potentially functions as a weapon for both the plants defending themselves against fungal or oomycete parasites, and for the pathogens trying to overcome the resisting barrier of the plants. This concept, however, had not been investigated in marine algae so far.

Intracellular eukaryotic pathogens in brown macroalgae in the Eastern Mediterranean, including LSU rRNA data for the oomycete Eurychasma dicksonii .

For the Mediterranean Sea, and indeed most of the world's oceans, the biodiversity and biogeography of eukaryotic pathogens infecting marine macroalgae remains poorly known, yet their ecological impact is probably significant. Based on 2 sampling campaigns on the Greek island of Lesvos in 2009 and 1 in northern Greece in 2012, this study provides first records of 3 intracellular eukaryotic pathogens infecting filamentous brown algae at these locations: Eurychasma dicksonii, Anisolpidium sphacellarum, and A. ectocarpii.

Avirulence protein 3a (AVR3a) from the potato pathogen Phytophthora infestans forms homodimers through its predicted translocation region and does not specifically bind phospholipids.

The mechanism of translocation of RxLR effectors from plant pathogenic oomycetes into the cytoplasm of their host is currently the object of intense research activity and debate. Here, we report the biochemical and thermodynamic characterization of the Phytophthora infestans effector AVR3a in vitro. We show that the amino acids surrounding the RxLR leader mediate homodimerization of the protein.

Development and characteristics of an adhesion bioassay for ectocarpoid algae.

Species of filamentous brown algae in the family Ectocarpaceae are significant members of fouling communities. However, there are few systematic studies on the influence of surface physico-chemical properties on their adhesion. In the present paper the development of a novel, laboratory-based adhesion bioassay for ectocarpoid algae, at an appropriate scale for the screening of sets of experimental samples in well-replicated and controlled experiments is described.

Highly dynamic exon shuffling in candidate pathogen receptors ... what if brown algae were capable of adaptive immunity?

Pathogen recognition is the first step of immune reactions. In animals and plants, direct or indirect pathogen recognition is often mediated by a wealth of fast-evolving receptors, many of which contain ligand-binding and signal transduction domains, such as leucine-rich or tetratricopeptide repeat (LRR/TPR) and NB-ARC domains, respectively. In order to identify candidates potentially involved in algal defense, we mined the genome of the brown alga Ectocarpus siliculosus for homologues of these genes and assessed the evolutionary pressures acting upon them.

A molecular insight into algal-oomycete warfare: cDNA analysis of Ectocarpus siliculosus infected with the basal oomycete Eurychasma dicksonii.

Brown algae are the predominant primary producers in coastal habitats, and like land plants are subject to disease and parasitism. Eurychasma dicksonii is an abundant, and probably cosmopolitan, obligate biotrophic oomycete pathogen of marine brown algae. Oomycetes (or water moulds) are pathogenic or saprophytic non-photosynthetic Stramenopiles, mostly known for causing devastating agricultural and aquacultural diseases.

DNA barcoding of oomycetes with cytochrome c oxidase subunit I and internal transcribed spacer.

Oomycete species occupy many different environments and many ecological niches. The genera Phytophthora and Pythium for example, contain many plant pathogens which cause enormous damage to a wide range of plant species. Proper identification to the species level is a critical first step in any investigation of oomycetes, whether it is research driven or compelled by the need for rapid and accurate diagnostics during a pathogen outbreak.

Comparative immunofluorescence and ultrastructural analysis of microtubule organization in Uronema sp., Klebsormidium flaccidum, K. subtilissimum, Stichococcus bacillaris and S. chloranthus (Chlorophyta).

A detailed comparative examination of microtubule (MT) organization in interphase and dividing cells of Uronema sp., Klebsormidium flaccidum, K. subtilissimum, Stichococcus bacillaris and S.

Algal diseases: spotlight on a black box.

Like any other living organisms, algae are plagued by diseases caused by fungi, protists, bacteria or viruses. As aquaculture continues to rise worldwide, pathogens of nori or biofuel sources are becoming a significant economic burden. Parasites are also increasingly being considered of equal importance with predators for ecosystem functioning.

Genome sequence of the necrotrophic plant pathogen Pythium ultimum reveals original pathogenicity mechanisms and effector repertoire.

Background: Pythium ultimum is a ubiquitous oomycete plant pathogen responsible for a variety of diseases on a broad range of crop and ornamental species.

Results: The P. ultimum genome (42.

The Ectocarpus genome and the independent evolution of multicellularity in brown algae.

Brown algae (Phaeophyceae) are complex photosynthetic organisms with a very different evolutionary history to green plants, to which they are only distantly related. 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.

Detection of differential host susceptibility to the marine oomycete pathogen Eurychasma dicksonii by real-time PCR: not all algae are equal.

In the marine environment, a growing body of evidence points to parasites as key players in the control of population dynamics and overall ecosystem structure. However, their prevalence and impact on marine macroalgal communities remain virtually unknown. Indeed, infectious diseases of seaweeds are largely underdocumented, partly because of the expertise required to diagnose them with a microscope.

The development, ultrastructural cytology, and molecular phylogeny of the basal oomycete Eurychasma dicksonii, infecting the filamentous phaeophyte algae Ectocarpus siliculosus and Pylaiella littoralis.

The morphological development, ultrastructural cytology, and molecular phylogeny of Eurychasma dicksonii, a holocarpic oomycete endoparasite of phaeophyte algae, were investigated in laboratory cultures. Infection of the host algae by E. dicksonii is initiated by an adhesorium-like infection apparatus.

The Culture Collection of Algae and Protozoa (CCAP): a biological resource for protistan genomics.

CCAP, the largest European protistan culture collection, is based at the Scottish Association for Marine Science near Oban, Scotland (http://www.ccap.ac.

Pathogen-responsive expression of glycosyltransferase genes UGT73B3 and UGT73B5 is necessary for resistance to Pseudomonas syringae pv tomato in Arabidopsis.

The genome sequencing of Arabidopsis (Arabidopsis thaliana) has revealed that secondary metabolism plant glycosyltransferases (UGTs) are encoded by an unexpectedly large multigenic family of 120 members. Very little is known about their actual function in planta, in particular during plant pathogen interactions. Among them, members of the group D are of particular interest since they are related to UGTs involved in stress-inducible responses in other plant species.

Plant secondary metabolism glycosyltransferases: the emerging functional analysis.

Glycosylation is a widespread modification of plant secondary metabolites. It is involved in various functions, including the regulation of hormone homeostasis, the detoxification of xenobiotics and the biosynthesis and storage of secondary compounds. In plants, these reactions are controlled by a specific subclass of the ubiquitous glycosyltransferase family.

Transcriptional co-regulation of secondary metabolism enzymes in Arabidopsis: functional and evolutionary implications.

The combined knowledge of the Arabidopsis genome and transcriptome now allows to get an integrated view of the dynamics and evolution of metabolic pathways in plants. We used publicly available sets of microarray data obtained in a wide range of different stress and developmental conditions to investigate the co-expression of genes encoding enzymes of secondary metabolism pathways, in particular indoles, phenylpropanoids, and flavonoids. We performed hierarchical clustering of gene expression profiles and found that major enzymes of each pathway display a clear and robust co-expression throughout all the conditions studied.