Symbiont-specific responses to environmental cues in a threesome lichen symbiosis.

Photosymbiodemes are a special case of lichen symbiosis where one lichenized fungus engages in symbiosis with two different photosynthetic partners, a cyanobacterium and a green alga, to develop two distinctly looking photomorphs. We compared gene expression of thallus sectors of the photosymbiodeme-forming lichen Peltigera britannica containing cyanobacterial photobionts with thallus sectors with both green algal and cyanobacterial photobionts and investigated differential gene expression at different temperatures representing mild and putatively stressful conditions. First, we quantified photobiont-mediated differences in fungal gene expression.

Large differences in carbohydrate degradation and transport potential among lichen fungal symbionts.

Lichen symbioses are thought to be stabilized by the transfer of fixed carbon from a photosynthesizing symbiont to a fungus. In other fungal symbioses, carbohydrate subsidies correlate with reductions in plant cell wall-degrading enzymes, but whether this is true of lichen fungal symbionts (LFSs) is unknown. Here, we predict genes encoding carbohydrate-active enzymes (CAZymes) and sugar transporters in 46 genomes from the Lecanoromycetes, the largest extant clade of LFSs.

Novel methods to characterise spatial distribution and enantiomeric composition of usnic acids in four Icelandic lichens.

Usnic acid is an antibiotic metabolite produced by a wide variety of lichenized fungal lineages. The enantiomers of usnic acid have been shown to display contrasting bioactivities, and hence it is important to determine their spatial distribution, amounts and enantiomeric ratios in lichens to understand their roles in nature and grasp their pharmaceutical potential. The overall aim of the study was to characterise the spatial distribution of the predominant usnic acid enantiomer in lichens by combining spatial imaging and chiral chromatography.

Faster nitrogen cycling and more fungal and root biomass in cold ecosystems under experimental warming: a meta-analysis.

Warming can alter the biogeochemistry and ecology of soils. These alterations can be particularly large in high northern latitude ecosystems, which are experiencing the most intense warming globally. In this meta-analysis, we investigated global trends in how experimental warming is altering the biogeochemistry of the most common limiting nutrient for biological processes in cold ecosystems of high northern latitudes (>50°): nitrogen (N).

The lichen symbiosis re-viewed through the genomes of Cladonia grayi and its algal partner Asterochloris glomerata.

Background: Lichens, encompassing 20,000 known species, are symbioses between specialized fungi (mycobionts), mostly ascomycetes, and unicellular green algae or cyanobacteria (photobionts). Here we describe the first parallel genomic analysis of the mycobiont Cladonia grayi and of its green algal photobiont Asterochloris glomerata. We focus on genes/predicted proteins of potential symbiotic significance, sought by surveying proteins differentially activated during early stages of mycobiont and photobiont interaction in coculture, expanded or contracted protein families, and proteins with differential rates of evolution.

Distinctive characters of Nostoc genomes in cyanolichens.

Background: Cyanobacteria of the genus Nostoc are capable of forming symbioses with a wide range of organism, including a diverse assemblage of cyanolichens. Only certain lineages of Nostoc appear to be able to form a close, stable symbiosis, raising the question whether symbiotic competence is determined by specific sets of genes and functionalities.

Results: We present the complete genome sequencing, annotation and analysis of two lichen Nostoc strains.

Fungal and cyanobacterial gene expression in a lichen symbiosis: Effect of temperature and location.

Organisms have evolved different cellular mechanisms to deal with environmental stress, primarily through complex molecular mechanisms including protein refolding and DNA repair. As mutualistic symbioses, lichens offer the possibility of analyzing molecular stress responses in a particularly tight interspecific relationship. We study the widespread cyanolichen Peltigera membranacea, a key player in carbon and nitrogen cycling in terrestrial ecosystems at northern latitudes.

Nutrient scavenging activity and antagonistic factors of non-photobiont lichen-associated bacteria: a review.

Lichens are defined as the specific symbiotic structure comprising a fungus and a green alga and/or cyanobacterium. Up until recently, non-photobiont endothallic bacteria, while known to be present in large numbers, have generally been dismissed as functionally irrelevant cohabitants of the lichen thallus, or even environmental contaminants. Recent analyses of lichen metagenomes and innovative co-culture experiments have uncovered a functionally complex community that appears to contribute to a healthy lichen thallus in several ways.

Two mutations in the vif gene of maedi-visna virus have different phenotypes, indicating more than one function of Vif.

Like most other lentiviruses, maedi-visna virus (MVV) requires Vif for replication in natural target cells and in vivo. Here, we show that Vif-deficient MVV accumulates G-A mutations in the sequence context characteristic of ovine APOBEC3, consistent with a role of MVV Vif in neutralizing APOBEC3. We studied two point mutations in the vif gene of MVV.

Analysis of the Peltigera membranacea metagenome indicates that lichen-associated bacteria are involved in phosphate solubilization.

Although lichens are generally described as mutualistic symbioses of fungi and photosynthetic partners, they also harbour a diverse non-phototrophic microbiota, which is now regarded as a significant part of the symbiosis. However, the role of the non-phototrophic microbiota within the lichen is still poorly known, although possible functions have been suggested, including phosphate solubilization and various lytic activities. In the present study we focus on the bacterial biota associated with the foliose lichen Peltigera membranacea.

Effects of abiotic stressors on lutein production in the green microalga Dunaliella salina.

Background: Recent years have witnessed a rising trend in exploring microalgae for valuable carotenoid products as the demand for lutein and many other carotenoids in global markets has increased significantly. In green microalgae lutein is a major carotenoid protecting cellular components from damage incurred by reactive oxygen species under stress conditions. In this study, we investigated the effects of abiotic stressors on lutein accumulation in a strain of the marine microalga D.

Metagenomic natural product discovery in lichen provides evidence for a family of biosynthetic pathways in diverse symbioses.

Bacteria are a major source of natural products that provide rich opportunities for both chemical and biological investigation. Although the vast majority of known bacterial metabolites derive from free-living organisms, increasing evidence supports the widespread existence of chemically prolific bacteria living in symbioses. A strategy based on bioinformatic prediction, symbiont cultivation, isotopic enrichment, and advanced analytics was used to characterize a unique polyketide, nosperin, from a lichen-associated Nostoc sp.

Studies on recombination processes in two Chlamydomonas reinhardtii endogenous genes, NIT1 and ARG7.

Integration of exogenous DNA in the unicellular green alga Chlamydomonas reinhardtii is principally carried out by mechanisms involving non-homologous recombination (NHR), rather than homologous recombination (HR). Homologous recombination is, however, the mechanism of choice when it comes to gene targeting. Unfortunately, attempts to establish this method in Chlamydomonas have had limited success.

LEC-2, a highly variable lectin in the lichen .

Lectins are a diverse group of carbohydrate binding proteins often involved in cellular interactions. A lectin gene, -, was identified in the mycobiont of the lichen . Sequencing of - open reading frames from 21 individual samples showed an unexpectedly high level of polymorphism in the deduced protein (LEC-2), which was sorted into nine haplotypes based on amino acid sequence.

Enhancement of carotenoid biosynthesis in the green microalga Dunaliella salina with light-emitting diodes and adaptive laboratory evolution.

There is a particularly high interest to derive carotenoids such as β-carotene and lutein from higher plants and algae for the global market. It is well known that β-carotene can be overproduced in the green microalga Dunaliella salina in response to stressful light conditions. However, little is known about the effects of light quality on carotenoid metabolism, e.

Mitochondrial genomes from the lichenized fungi Peltigera membranacea and Peltigera malacea: features and phylogeny.

Mitochondrial genomes from the fungal partners of two terricolous foliose lichen symbioses, Peltigera membranacea and Peltigera malacea, have been determined using metagenomic approaches, including RNA-seq. The roughly 63 kb genomes show all the major features found in other Pezizomycotina, such as unidirectional transcription, 14 conserved protein genes, genes for the two subunit rRNAs and for a set of 26 tRNAs used in translating the 62 amino acid codons. In one of the tRNAs a CAU anticodon is proposed to be modified, via the action of the nuclear-encoded enzyme, tRNA Ile lysidine synthase, so that it recognizes the codon AUA (Ile) instead of AUG (Met).

Cloning and heterologous transcription of a polyketide synthase gene from the lichen Solorina crocea.

Lichens and most ascomycete fungi produce polyketide secondary metabolites often with valuable biological activities. Their biosynthesis is primarily governed by large iterative multifunctional type I polyketide synthases. Although there has been good progress studying filamentous non-lichenized fungi, there is limited information on polyketide biosynthesis in lichens and their mycobionts, due to their slow growth, difficulties in establishing pure cultures, and the absence of methods for direct genetic manipulation.

Mutational analysis of a principal neutralization domain of visna/maedi virus envelope glycoprotein.

We have shown previously that a type-specific neutralization domain is located within a 39 aa sequence in the fourth variable domain of gp135 in visna/maedi virus. We now show that neutralizing antibodies detected early in infection are directed to this epitope, suggesting an immunodominant nature of this domain. Ten antigenic variants were previously analysed for mutations in this region, and all but one were found to be mutated.

Duplicated sequence motif in the long terminal repeat of maedi-visna virus extends cell tropism and is associated with neurovirulence.

Maedi-visna virus (MVV) is a lentivirus of sheep causing chronic inflammatory disease of the lungs (maedi) and the nervous system (visna). We have previously shown that a duplicated sequence in the long terminal repeat (LTR) of MVV is a determinant of cell tropism. Here, we demonstrate that deletion of a CAAAT sequence from either one of the repeats resulted in poor virus growth in sheep choroid plexus cells.

Optimization of heterologous production of the polyketide 6-MSA in Saccharomyces cerevisiae.

Polyketides are a group of natural products that have gained much interest due to their use as antibiotics, cholesterol lowering agents, immunosuppressors, and as other drugs. Many organisms that naturally produce polyketides are difficult to cultivate and only produce these metabolites in small amounts. It is therefore of general interest to transfer polyketide synthase (PKS) genes from their natural sources into heterologous hosts that can over-produce the corresponding polyketides.

Simultaneous mutations in CA and Vif of Maedi-Visna virus cause attenuated replication in macrophages and reduced infectivity in vivo.

Maedi-visna virus (MVV) is a lentivirus of sheep sharing several key features with the primate lentiviruses. The virus causes slowly progressive diseases, mainly in the lungs and the central nervous system of sheep. Here, we investigate the molecular basis for the differential growth phenotypes of two MVV isolates.

Mucosal vaccination with an attenuated maedi-visna virus clone.

Four sheep were infected intratracheally with an attenuated molecular clone of maedi-visna virus (MVV). All four became infected. Ten months later these sheep were challenged intratracheally with a genetically similar but pathogenic clone of MVV.

The vif gene of maedi-visna virus is essential for infectivity in vivo and in vitro.

We have investigated the role of vif in maedi-visna virus (MVV), a lentivirus of sheep, by studying in vitro replication of vif-deleted MVV in several cell types, and the effects of vif deletion on in vivo infection. By measuring RT activity, we found that in comparison to wild-type MVV, growth of vif-deleted MVV was similar in fetal ovine synovial (FOS) cells, highly attenuated in sheep choroid plexus (SCP) cells, and not detectable in macrophages, natural target cells of MVV. Productive infection by vif-deleted MVV could not be demonstrated in sheep.

The long terminal repeat is a determinant of cell tropism of maedi-visna virus.

Maedi-visna virus (MVV) is a lentivirus of sheep, mainly affecting the lungs and the central nervous system. Long terminal repeat (LTR) sequence variability is common in tissue culture-derived isolates of MVV as well as those of other lentiviruses. The role of this sequence variation in MVV replication has not been explored.