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

Atrial electrophysiological characteristics of aging

Introduction: Advancing age is a known risk factor for developing atrial fibrillation (AF), yet it is unknown which electrophysiological changes contribute to this increased susceptibility. The goal of this study is to investigate conduction disturbances and unipolar voltages (UV) related to aging. Methods: We included 216 patients (182 male, age: 36–83 years) without a history of AF undergoing elective coronary artery bypass surgery. Five seconds of sinus rhythm were recorded intraoperatively at the right atrium (RA), Bachmann's bundle (BB), the left atrium and the pulmonary vein area (PVA). Conduction delay (CD), -block (CB), -velocity (CV), length of longest CB lines and UV were assessed in all regions. Results: With aging, increasing conduction disturbances were found, particularly at RA and BB (RA: longest CB line rs =.158, p =.021; BB: CB prevalence rs =.206, p =.003; CV rs = −.239, p <.0005). Prevalence of low UV areas (UV <5th percentile) increased with aging at the BB and PVA (BB: rs =.237, p <.0005 and PVA: rs =.228, p =.001). Conclusions: Aging is accompanied by an increase in conduction disturbances during sinus rhythm and a higher prevalence of low UV areas, particularly at BB and in the RA. These electrophysiological alterations could in part explain the increasing susceptibility to AF development associated with aging

Atrial electrophysiological characteristics of aging

Introduction: Advancing age is a known risk factor for developing atrial fibrillation (AF), yet it is unknown which electrophysiological changes contribute to this increased susceptibility. The goal of this study is to investigate conduction disturbances and unipolar voltages (UV) related to aging. Methods: We included 216 patients (182 male, age: 36–83 years) without a history of AF undergoing elective coronary artery bypass surgery. Five seconds of sinus rhythm were recorded intraoperatively at the right atrium (RA), Bachmann's bundle (BB), the left atrium and the pulmonary vein area (PVA). Conduction delay (CD), -block (CB), -velocity (CV), length of longest CB lines and UV were assessed in all regions. Results: With aging, increasing conduction disturbances were found, particularly at RA and BB (RA: longest CB line rs =.158, p =.021; BB: CB prevalence rs =.206, p =.003; CV rs = −.239, p <.0005). Prevalence of low UV areas (UV <5th percentile) increased with aging at the BB and PVA (BB: rs =.237, p <.0005 and PVA: rs =.228, p =.001). Conclusions: Aging is accompanied by an increase in conduction disturbances during sinus rhythm and a higher prevalence of low UV areas, particularly at BB and in the RA. These electrophysiological alterations could in part explain the increasing susceptibility to AF development associated with aging

EBR1 genomic expansion and its role in virulence of <em>Fusarium</em> species

International audienceGenome sequencing of Fusarium oxysporum revealed that pathogenic forms of this fungus harbour supernumerary chromosomes with a wide variety of genes, many of which likely encode traits required for pathogenicity or niche specialization. Specific transcription factor gene families are expanded on these chromosomes including the EBR1 family (Enhanced Branching). The significance of the EBR1 family expansion on supernumerary chromosomes and whether EBR1 paralogues are functional is currently unknown. EBR1 is found as a single copy in F. graminearum and other fungi but as multiple paralogues in pathogenic F. oxysporum strains. These paralogues exhibit sequence and copy number variation among different host-specific strains and even between more closely related strains. Relative expression of the EBR1 paralogues depends on growth conditions and on the presence of the single EBR1 gene in the core genome. Deletion of EBR1 in the core genome in different F. oxysporum strains resulted in impaired growth, reduced pathogenicity and slightly reduced biocontrol capacities. To identify genes regulated by EBR1, the transcriptomes of wild-type and Delta ebr1 strains were compared for both F. oxysporum and F. graminearum. These studies showed that in both species, EBR1 regulates genes involved in general metabolism as well as virulence