Murein and pseudomurein cell wall binding domains of bacteria and archaea—a comparative view

The cell wall, a major barrier protecting cells from their environment, is an essential compartment of both bacteria and archaea. It protects the organism from internal turgor pressure and gives a defined shape to the cell. The cell wall serves also as an anchoring surface for various proteins and acts as an adhesion platform for bacteriophages. The walls of bacteria and archaea are mostly composed of murein and pseudomurein, respectively. Cell wall binding domains play a crucial role in the non-covalent attachment of proteins to cell walls. Here, we give an overview of the similarities and differences in the biochemical and functional properties of the two major murein and pseudomurein cell wall binding domains, i.e., the Lysin Motif (LysM) domain (Pfam PF01476) and the pseudomurein binding (PMB) domain (Pfam PF09373) of bacteria and archaea, respectively

Contribution of NFP LysM Domains to the Recognition of Nod Factors during the Medicago truncatula/Sinorhizobium meliloti Symbiosis

The root nodule nitrogen fixing symbiosis between legume plants and soil bacteria called rhizobia is of great agronomical and ecological interest since it provides the plant with fixed atmospheric nitrogen. The establishment of this symbiosis is mediated by the recognition by the host plant of lipo-chitooligosaccharides called Nod Factors (NFs), produced by the rhizobia. This recognition is highly specific, as precise NF structures are required depending on the host plant. Here, we study the importance of different LysM domains of a LysM-Receptor Like Kinase (LysM-RLK) from Medicago truncatula called Nod factor perception (NFP) in the recognition of different substitutions of NFs produced by its symbiont Sinorhizobium meliloti. These substitutions are a sulphate group at the reducing end, which is essential for host specificity, and a specific acyl chain at the non-reducing end, that is critical for the infection process. The NFP extracellular domain (ECD) contains 3 LysM domains that are predicted to bind NFs. By swapping the whole ECD or individual LysM domains of NFP for those of its orthologous gene from pea, SYM10 (a legume plant that interacts with another strain of rhizobium producing NFs with different substitutions), we showed that NFP is not directly responsible for specific recognition of the sulphate substitution of S. meliloti NFs, but probably interacts with the acyl substitution. Moreover, we have demonstrated the importance of the NFP LysM2 domain for rhizobial infection and we have pinpointed the importance of a single leucine residue of LysM2 in that step of the symbiosis. Together, our data put into new perspective the recognition of NFs in the different steps of symbiosis in M. truncatula, emphasising the probable existence of a missing component for early NF recognition and reinforcing the important role of NFP for NF recognition during rhizobial infection

Sequential Delivery of Host-Induced Virulence Effectors by Appressoria and Intracellular Hyphae of the Phytopathogen Colletotrichum higginsianum

Phytopathogens secrete effector proteins to manipulate their hosts for effective colonization. Hemibiotrophic fungi must maintain host viability during initial biotrophic growth and elicit host death for subsequent necrotrophic growth. To identify effectors mediating these opposing processes, we deeply sequenced the transcriptome of Colletotrichum higginsianum infecting Arabidopsis. Most effector genes are host-induced and expressed in consecutive waves associated with pathogenic transitions, indicating distinct effector suites are deployed at each stage. Using fluorescent protein tagging and transmission electron microscopy-immunogold labelling, we found effectors localised to stage-specific compartments at the host-pathogen interface. In particular, we show effectors are focally secreted from appressorial penetration pores before host invasion, revealing new levels of functional complexity for this fungal organ. Furthermore, we demonstrate that antagonistic effectors either induce or suppress plant cell death. Based on these results we conclude that hemibiotrophy in Colletotrichum is orchestrated through the coordinated expression of antagonistic effectors supporting either cell viability or cell death

FIRST ANALYSIS OF GENETIC VARIABILITY IN CARINTHIAN POPULATIONS OF THE WHITE-CLAWED CRAYFISH AUSTROPOTAMOBIUS PALLIPES

Several authors have speculated about the nativeness of the white-clawed crayfish (Austropotamobius pallipes) in the Austrian province of Carinthia, since this is the only occurrence of the species within the Danube river system. Phylogeographic analyses based on mitochondrial DNA sequences showed that Carinthian A. pallipes are closely related to specimens from Slovenia, Croatia and north-eastern Italy. These analyses additionally pointed to an absence of variability among populations in Carinthia. In the present study a larger number of individuals sampled from three different brooks in western Carinthia was investigated by analysing sequences of the mtDNA cytochrome c oxidase gene (COI), microsatellite DNA and microsatellite length variation in the nuclear ribosomal DNA internal transcribed spacer region (ITS1). Not only COI sequences revealed low degrees of genetic variability, but also microsatellite loci displayed low allelic diversity and low heterozygosity. Analysis of ITS1 microsatellite length variation in turn showed high levels of intragenomic variability, since single individuals manifested up to seven distinct fragments. Microsatellite data and ITS1 microsatellite length variation analyses also revealed significant differentiation among some population pairs. Since genetic divergence was mainly based on differences in allele frequencies and not on the occurrence of alternative alleles, we assume that Carinthian populations became isolated rather recently and that the occurrence of this species in this region is more likely to be a result of human introduction than of natural postglacial colonisation

UPDATE OF THE MOLECULAR PHYLOGENY OF THE AUSTROPOTAMOBIUS PALLIPES SPECIES COMPLEX BY INCLUDING SPECIMENS FROM SOUTH TYROL (ITALY) AND CARINTHIA (AUSTRIA)

The phylogenetic relationships of the Austropotamobius pallipes species complex were assessed in several recent genetic studies by analysing sequences of the mitochondrial DNA. Although the Alpine region is known to harbour great extents of morphological and genetic diversity, none of the previous studies included populations from South Tyrol in Northern Italy and Carinthia in Southern Austria. In order to clarify their taxonomic status white-clawed crayfish were sampled from six populations in South Tyrol and three populations in Carinthia. Phylogenetic analyses are based on partial DNA sequences of the mitochondrial DNA 16S rRNA gene, which were supplemented with sequences deposited in GenBank. All surveyed individuals from the six populations in South Tyrol comprised a single haplotype that equalled the already described haplotype S3. This haplotype is distributed in Plansee (Austria) as well as several other localities in Italy and Switzerland, and belongs to the A. italicus carinthiacus clade. The investigated specimens from all three Carinthian populations also displayed one single haplotype. However, this haplotype clustered in the A. italicus carsicus clade and has not been published before. Our study clearly shows that neither Austrian crayfish populations from Plansee and Carinthia, nor populations from South Tyrol and Carinthia belong to the same phylogenetic lineage

A reality check for the applicability of comprehensive climate risk assessment and management: Experiences from Peru, India and Austria

Climate-related risks are a major threat to humanity, affecting the lives and livelihoods of communities globally. Even with adaptation, climate change is projected to increase the severity of risks, leading to impacts and residual risks, also termed losses and damages. Frameworks and approaches using Climate Risk Management (CRM), an integration of Disaster Risk Reduction, Climate Change Adaptation, and sustainable development, are being devised to support the comprehensive management of increasing climate-related risks. Here we discuss to what extent comprehensive CRM has been implemented in three specific cases – in Peru, India and Austria. The approach is conceptually represented and evaluated using a CRM framework. The cases deal with risks associated with glacial lake outburst floods, sea level rise, tropical cyclones, salinization, riverine floods and agricultural droughts. Ultimately, we synthesise policy and research recommendations to help understand what is feasible for CRM approaches applied in practice. We find that successful CRM implementation in practice benefits from being flexible, and participatory from beginning to end, whilst considering compounding risks, and the spectrum of (just and equitable) incremental to transformational adaptation measures necessary for attending to current and projected future increases in climate-related risks

A poly(A) ribonuclease controls the cellotriose-based interaction between Piriformospora indica and its host Arabidopsis

Piriformospora indica, an endophytic root-colonizing fungus, efficiently promotes plant growth and induces resistance to abiotic stress and biotic diseases. The fungal cell wall extract induces cytoplasmic calcium [Ca2+]cyt elevation in host plant roots. Here, we show that an elici-tor-active cell wall moiety, released by P. indica into the medium, is cellotriose (CT). CT in-duces a mild defense-like response including the production of reactive oxygen species, changes in membrane potentials and the expression of genes involved in growth regulation and root development. CT based [Ca2+]cyt elevation in Arabidopsis roots does not require BAK1 coreceptor, or the putative Ca2+ channels TPC1, GLR3.3, -2.4 and -2.5 and operates synergistically with the elicitor chitin. We identified an ethylmethane-sulfonate-induced mu-tant ([Ca2+]cyt elevation mutant, cycam) impaired in response to CT, cellooligomers (n = 2, 4-7), but not to chitooligomers (n = 4-8) in roots. The mutant contains a single nucleotide ex-change in the gene encoding for a poly(A) ribonuclease (AtPARN, At1g55870) which de-grades poly(A) tails of specific mRNAs. The wild-type PARN cDNA, expressed under the control of a 35S promoter, complements the mutant phenotype. Our finding of cellotriose as a novel chemical mediator might help to understand the complex P. indica-plant mutual rela-tionship in beneficial symbiosis

Towards improved adaptation action in Europe: Policy recommendations from the UNCHAIN project

Policymakers can make adaptation "smarter" by using the Impact Chain approach to analyse both conventional local climate risks and lesser well-known transboundary climate risks. • Policymakers should embrace uncertainties by applying a reflect-then-act rather than the predict-then-act approach; by including socioeconomic scenarios for a range of possible developments, from likely to unanticipated; and by ensuring transparency in communications. Below we summarize our policy-relevant insights and recommendations for the European Commission and EU member states