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Information on the ecology of invertebrate communities populating Macrocystis pyrifera forests in the Falkland Islands is scarce. Indeed, the factors influencing diversity, distribution and community structure have never been studied here. Benthic photoquadrats were collected along three permanent 20 m transects at three depth strata (shallow 5–10 m; middle 10–15 m; deep 15–20 m) off the coast of Kidney Island, Falkland Islands from Austral summer 2009 to Austral spring 2010. 146 taxa comprising 10 phyla and 21 classes were recorded during the surveys, with the most abundant sessile and vagile taxa being Spirorbinid worms and the hermit crab Pagurus comptus, respectively. Community structure was influenced by depth, with highest species richness in the middle depth stratum, and strong contrasts between the communities in the shallow and deep depth strata. Influence of season on community structure was evident, though not as strong a factor as depth. Spring and summer months were most species rich, demonstrating a difference between the shallow subtidal regions of Patagonia where species richness was reported to be highest in Austral autumn and winter. The effect of substrate and depth was also investigated for the abundance of individual taxa. This study provides the first description of the fauna and flora of shallow rocky reefs in the Falkland Islands, describing how these communities change over small spatial and temporal scales. The outcomes of this investigation contribute to better understanding ecological patterns of the Falklands shallow benthic environments and adds knowledge to the biogeography of the South Atlantic. [ABSTRACT FROM AUTHOR]

The animal-pathogenic oomycete Saprolegnia parasitica causes serious losses in aquaculture by infecting and killing freshwater fish. Like plant-pathogenic oomycetes, S. parasitica employs similar infection structures and secretes effector proteins that translocate into host cells to manipulate the host. Here, we show that the host-targeting protein SpHtp3 enters fish cells in a pathogen-independent manner. This uptake process is guided by a gp96-like receptor and can be inhibited by supramolecular tweezers. The C-terminus of SpHtp3 (containing the amino acid sequence YKARK), and not the N-terminal RxLR motif, is responsible for the uptake into host cells. Following translocation, SpHtp3 is released from vesicles into the cytoplasm by another host-targeting protein where it degrades nucleic acids. The effector translocation mechanism described here, is potentially also relevant for other pathogen--host interactions as gp96 is found in both animals and plants. [ABSTRACT FROM AUTHOR]

Bacterial, oomycete and fungal plant pathogens establish disease by translocation of effector proteins into host cells, where they may directly manipulate host innate immunity. In bacteria, translocation is through the type III secretion system, but analogous processes for effector delivery are uncharacterized in fungi and oomycetes. Here we report functional analyses of two motifs, RXLR and EER, present in translocated oomycete effectors. We use the Phytophthora infestans RXLR-EER-containing protein Avr3a as a reporter for translocation because it triggers RXLR-EER-independent hypersensitive cell death following recognition within plant cells that contain the R3a resistance protein. We show that Avr3a, with or without RXLR-EER motifs, is secreted from P. infestans biotrophic structures called haustoria, demonstrating that these motifs are not required for targeting to haustoria or for secretion. However, following replacement of Avr3a RXLR-EER motifs with alanine residues, singly or in combination, or with residues KMIK-DDK—representing a change that conserves physicochemical properties of the protein—P. infestans fails to deliver Avr3a or an Avr3a–GUS fusion protein into plant cells, demonstrating that these motifs are required for translocation. We show that RXLR-EER-encoding genes are transcriptionally upregulated during infection. Bioinformatic analysis identifies 425 potential genes encoding secreted RXLR-EER class proteins in the P. infestans genome. Identification of this class of proteins provides unparalleled opportunities to determine how oomycetes manipulate hosts to establish infection. [ABSTRACT FROM AUTHOR]

From a set of Phytophthora infestans cDNA clones that were randomly selected from a potato- P. infestans interaction cDNA library, a relatively high proportion (5 out of 22) appeared to be derived from the same gene. The gene was designated ric1. P. infestans contains two copies of ric1 which share 98% homology at the nucleotide-sequence level and 100% at the amino-acid level. The nucleotide sequence predicts an open reading frame of 171 bp encoding a 57 amino-acid hydrophobic-peptide with two potential membrane-spanning domains. The predicted peptide shows high homology to a peptide encoded by plant genes whose expression is specifically induced during stress conditions. Southern-blot analysis of genomic DNA of several Phytophthora species indicated that most species contain ric1 homologues. During the life cycle of P. infestans, ric1 was expressed in all developmental stages but the level of expression varied. Sporangia and germinating cysts appeared to contain only very little ric1 mRNA whereas in the mycelium and during in planta growth higher levels were detected. Subjecting the mycelium to osmotic stress or to a high pH resulted in increased ric1 expression. [ABSTRACT FROM AUTHOR]

A transgenic Phytophthora infestans strain that constitutively produces and secretes β-glucuronidase (GUS) was used in detached leaf assays to quantify the levels of resistance to late blight in potato cultivars Surprise, Irene, Pimpernel, Alpha and Bintje. Four days after inoculation levels of GUS activity were determined in infected leaves. Significant differences between the various cultivars were observed. Discrimination between resistant and susceptible cultivars was possible based solely on levels of GUS activity. Regression analysis revealed a positive correlation between in planta GUS levels and field resistance expressed as Area under Disease Progress Curve (ADPC). [ABSTRACT FROM AUTHOR]

Aphanomyces invadans, the causative agent of epizootic ulcerative syndrome, is one of the most destructive pathogens of freshwater fishes. To date, the disease has been reported from over 160 fish species in 20 countries and notably, this is the first non-salmonid disease that has resulted in major impacts globally. In particular, Indian major carps (IMCs) are highly susceptible to this disease. To increase our knowledge particularly with regards to host immune response against A. invadans infection in a susceptible host, the gene expression profile in head kidney of A. invadans-infected and control rohu, Labeo rohita was investigated using RNA sequencing. Time course analysis of RNA-Seq data revealed 5608 differentially expressed genes, involved among others in Antigen processing and presentation, Leukocyte transendothelial migration, IL-17 signaling, Chemokine signaling, C-type lectin receptor signaling and Toll-like receptor signaling pathways. In the affected pathways, a number of immune genes were found to be downregulated, suggesting an immune evasion strategy of A. invadans in establishing the infection. The information generated in this study offers first systematic mechanistic understanding of the host–pathogen interaction that might underpin the development of new management strategies for this economically devastating fish-pathogenic oomycete A. invadans. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

Animals and plants are increasingly suffering from diseases caused by fungi and oomycetes. These emerging pathogens are now recognized as a global threat to biodiversity and food security. Among oomycetes, Saprolegnia species cause significant declines in fish and amphibian populations. Fish eggs have an immature adaptive immune system and depend on nonspecific innate defences to ward off pathogens. Here, meta-taxonomic analyses revealed that Atlantic salmon eggs are home to diverse fungal, oomycete and bacterial communities. Although virulent Saprolegnia isolates were found in all salmon egg samples, a low incidence of Saprolegniosis was strongly correlated with a high richness and abundance of specific commensal Actinobacteria, with the genus Frondihabitans (Microbacteriaceae) effectively inhibiting attachment of Saprolegniato salmon eggs. These results highlight that fundamental insights into microbial landscapes of fish eggs may provide new sustainable means to mitigate emerging diseases. [ABSTRACT FROM AUTHOR]