Haplotype diversity and phylogeny within Alternaria alternata and A. arborescens species complexes from tomatoes.

Tomato (Solanum lycopersicum L.) is an economically important vegetable susceptible to various fungal diseases, including leaf spot caused by Alternaria spp. from the section Alternaria.

Xanthone Inhibitors of Unfolded Protein Response Isolated from .

The unfolded protein response (UPR) is a key component of fungal virulence. The prenylated xanthone γ-mangostin isolated from (Clusiaceae) fruit pericarp, has recently been described to inhibit this fungal adaptative pathway. Considering that (Calophyllaceae) is known for its high prenylated xanthone content, its stem bark extract was fractionated using a bioassay-guided procedure based on the cell-based anti-UPR assay.

Natural Products Targeting the Fungal Unfolded Protein Response as an Alternative Crop Protection Strategy.

Discovering new solutions for crop protection is a major challenge for the next decades as a result of the ecotoxicological impact of classical fungicides, the emergence of fungicide resistances, and the consequence of climate change on pathogen distribution. Previous work on fungal mutants deficient in the unfolded protein response (UPR) supported that targeting this pathway is a promising plant disease control strategy. In particular, we showed that the UPR is involved in fungal virulence by altering cell protection against host defense compounds, such as phytoalexins and phytoanticipins.

In silico analysis of RNA interference components and miRNAs-like RNAs in the seed-borne necrotrophic fungus Alternariabrassicicola.

RNA interference is a mechanism of suppressing gene expression in plants, animals and fungi. This regulation mechanism involves three main enzymes, Dicers (Dcr), Argonautes (Ago) and RNA Dependent RNA Polymerases (Rdrp) allowing to produce smallRNAs. RNA interference and smallRNAs have a role in the plant-microorganisms interaction, either in a pathogenic or in a symbiotic relationships.

Characterization of New Small-Spored Species Isolated from in Algeria.

Although large-spored species of the section are considered to be the major agents responsible for leaf spot and blight of , small-spored species are also frequently isolated from symptomatic tissues. A survey of the north-western regions of Algeria during the 2017-2018 growing seasons revealed that amongst the 623 isolates from tomato, potato, pepper, eggplant and black nightshade, 8% could not be morphologically assigned to either section or section . In order to more precisely determine the taxonomic position of these isolates, detailed morphological characterizations and multi-locus phylogenetic analyses were performed.

Responses of the Necrotrophic Fungus to the Indolic Phytoalexin Brassinin.

causes black spot disease in . During host infection, this necrotrophic fungus is exposed to various antimicrobial compounds, such as the phytoalexin brassinin which is produced by many cultivated species. To investigate the cellular mechanisms by which this compound causes toxicity and the corresponding fungal adaptive strategies, we first analyzed fungal transcriptional responses to short-term exposure to brassinin and then used additional functional approaches.

Occurrence of Leaf Spot Disease Caused by (Sacc.) Rands on Jimson Weed and Potential Additional Host Plants in Algeria.

A leaf spot pathogen sp. was recovered from jimson weed, tomato, parsley, and coriander collected during surveys of blight diseases on and in Algeria. This species produced large conidial body generating long apical beaks that tapered gradually from a wide base to a narrow tip and short conidiophores originating directly from the agar surface.

Role of membrane compartment occupied by Can1 (MCC) and eisosome subdomains in plant pathogenicity of the necrotrophic fungus Alternaria brassicicola.

Background: MCC/eisosomes are membrane microdomains that have been proposed to participate in the plasma membrane function in particular by regulating the homeostasis of lipids, promoting the recruitment of specific proteins and acting as provider of membrane reservoirs.

Results: Here we showed that several potential MCC/eisosomal protein encoding genes in the necrotrophic fungus A. brassicicola were overexpressed when germinated spores were exposed to antimicrobial defence compounds, osmotic and hydric stresses, which are major constraints encountered by the fungus during the plant colonization process.

Responses to Hydric Stress in the Seed-Borne Necrotrophic Fungus .

is a necrotrophic fungus causing black spot disease and is an economically important seed-borne pathogen of cultivated brassicas. Seed transmission is a crucial component of its parasitic cycle as it promotes long-term survival and dispersal. Recent studies, conducted with the pathosystem, showed that the level of susceptibility of the fungus to water stress strongly influenced its seed transmission ability.

Genome Sequence of the Necrotrophic Plant Pathogen Abra43.

causes dark spot (or black spot) disease, which is one of the most common and destructive fungal diseases of spp. worldwide. Here, we report the draft genome sequence of strain Abra43.

A flavoprotein supports cell wall properties in the necrotrophic fungus .

Background: Flavin-dependent monooxygenases are involved in key biological processes as they catalyze a wide variety of chemo-, regio- and enantioselective oxygenation reactions. Flavoprotein monooxygenases are frequently encountered in micro-organisms, most of which require further functional and biocatalytic assessment. Here we investigated the function of the gene, which encodes a group A flavin monooxygenase in the plant pathogenic fungus , by generating a deficient mutant and examining its phenotype.

Differences in stability of seed-associated microbial assemblages in response to invasion by phytopathogenic microorganisms.

Seeds are involved in the vertical transmission of microorganisms from one plant generation to another and consequently act as reservoirs for the plant microbiota. However, little is known about the structure of seed-associated microbial assemblages and the regulators of assemblage structure. In this work, we have assessed the response of seed-associated microbial assemblages of Raphanus sativus to invading phytopathogenic agents, the bacterial strain Xanthomonas campestris pv.

Glucosinolate-derived isothiocyanates impact mitochondrial function in fungal cells and elicit an oxidative stress response necessary for growth recovery.

Glucosinolates are brassicaceous secondary metabolites that have long been considered as chemical shields against pathogen invasion. Isothiocyanates (ITCs), are glucosinolate-breakdown products that have negative effects on the growth of various fungal species. We explored the mechanism by which ITCs could cause fungal cell death using Alternaria brassicicola, a specialist Brassica pathogens, as model organism.

Characterization of glutathione transferases involved in the pathogenicity of Alternaria brassicicola.

Background: Glutathione transferases (GSTs) represent an extended family of multifunctional proteins involved in detoxification processes and tolerance to oxidative stress. We thus anticipated that some GSTs could play an essential role in the protection of fungal necrotrophs against plant-derived toxic metabolites and reactive oxygen species that accumulate at the host-pathogen interface during infection.

Results: Mining the genome of the necrotrophic Brassica pathogen Alternaria brassicicola for glutathione transferase revealed 23 sequences, 17 of which could be clustered into the main classes previously defined for fungal GSTs and six were 'orphans'.

Emergence shapes the structure of the seed microbiota.

Seeds carry complex microbial communities, which may exert beneficial or deleterious effects on plant growth and plant health. To date, the composition of microbial communities associated with seeds has been explored mainly through culture-based diversity studies and therefore remains largely unknown. In this work, we analyzed the structures of the seed microbiotas of different plants from the family Brassicaceae and their dynamics during germination and emergence through sequencing of three molecular markers: the ITS1 region of the fungal internal transcribed spacer, the V4 region of 16S rRNA gene, and a species-specific bacterial marker based on a fragment of gyrB.

Partial resistance of carrot to Alternaria dauci correlates with in vitro cultured carrot cell resistance to fungal exudates.

Although different mechanisms have been proposed in the recent years, plant pathogen partial resistance is still poorly understood. Components of the chemical warfare, including the production of plant defense compounds and plant resistance to pathogen-produced toxins, are likely to play a role. Toxins are indeed recognized as important determinants of pathogenicity in necrotrophic fungi.

Phosphoproteome profiles of the phytopathogenic fungi Alternaria brassicicola and Botrytis cinerea during exponential growth in axenic cultures.

This study describes the gel-free phosphoproteomic analysis of the phytopathogenic fungi Alternaria brassicicola and Botrytis cinerea grown in vitro under nonlimiting conditions. Using a combination of strong cation exchange and IMAC prior to LC-MS, we identified over 1350 phosphopeptides per fungus representing over 800 phosphoproteins. The preferred phosphorylation sites were found on serine (>80%) and threonine (>15%), whereas phosphorylated tyrosine residues were found at less than 1% in A.

First Report of Umbel Browning and Stem Necrosis Caused by Diaporthe angelicae on Carrot in France.

In 2011, carrot (Daucus carota L.) seed production occurred on 2,900 ha, which accounts for approximately 25% of the area devoted to the production of vegetable fine seeds. Since 2007, symptoms of umbel browning have been regularly observed in carrot production areas located in the central region.

Impact of the UPR on the virulence of the plant fungal pathogen A. brassicicola.

The fungal genus Alternaria contains many destructive plant pathogens, including Alternaria brassicicola, which causes black spot disease on a wide range of Brassicaceae plants and which is routinely used as a model necrotrophic pathogen in studies with Arabidopsis thaliana. During host infection, many fungal proteins that are critical for disease progression are processed in the endoplasmic reticulum (ER)/Golgi system and secreted in planta. The unfolded protein response (UPR) is an essential part of ER protein quality control that ensures efficient maturation of secreted and membrane-bound proteins in eukaryotes.

Dehydrin-like proteins in the necrotrophic fungus Alternaria brassicicola have a role in plant pathogenesis and stress response.

In this study, the roles of fungal dehydrin-like proteins in pathogenicity and protection against environmental stresses were investigated in the necrotrophic seed-borne fungus Alternaria brassicicola. Three proteins (called AbDhn1, AbDhn2 and AbDhn3), harbouring the asparagine-proline-arginine (DPR) signature pattern and sharing the characteristic features of fungal dehydrin-like proteins, were identified in the A. brassicicola genome.

Role of mannitol metabolism in the pathogenicity of the necrotrophic fungus Alternaria brassicicola.

In this study, the physiological functions of fungal mannitol metabolism in the pathogenicity and protection against environmental stresses were investigated in the necrotrophic fungus Alternaria brassicicola. Mannitol metabolism was examined during infection of Brassica oleracea leaves by sequential HPLC quantification of the major soluble carbohydrates and expression analysis of genes encoding two proteins of mannitol metabolism, i.e.

The Arabidopsis thaliana-Alternaria brassicicola pathosystem: A model interaction for investigating seed transmission of necrotrophic fungi.

Background: Seed transmission constitutes a major component of the parasitic cycle for several fungal pathogens. However, very little is known concerning fungal or plant genetic factors that impact seed transmission and mechanisms underlying this key biological trait have yet to be clarified. Such lack of available data could be probably explained by the absence of suitable model pathosystem to study plant-fungus interactions during the plant reproductive phase.

Methods for investigating the UPR in filamentous fungi.

Filamentous fungi have a high-capacity secretory system and are therefore widely exploited for the industrial production of native and heterologous proteins. However, in most cases, the yields of nonfungal proteins are significantly lower than those obtained for fungal proteins. One well-studied bottleneck appears to be the result of slow or aberrant folding of heterologous proteins in the ER during the early stages of secretion within the endoplasmic reticulum, leading to stress responses in the host, including the unfolded protein response (UPR).

Impact of the unfolded protein response on the pathogenicity of the necrotrophic fungus Alternaria brassicicola.

The unfolded protein response (UPR) is an important stress signalling pathway involved in the cellular development and environmental adaptation of fungi. We investigated the importance of the UPR pathway in the pathogenicity of the plant necrotrophic fungus Alternaria brassicicola, which causes black spot disease on a wide range of Brassicaceae. We identified the AbHacA gene encoding the major UPR transcription regulator in A.

Cell wall integrity and high osmolarity glycerol pathways are required for adaptation of Alternaria brassicicola to cell wall stress caused by brassicaceous indolic phytoalexins.

Camalexin, the characteristic phytoalexin of Arabidopsis thaliana, inhibits growth of the fungal necrotroph Alternaria brassicicola. This plant metabolite probably exerts its antifungal toxicity by causing cell membrane damage. Here we observed that activation of a cellular response to this damage requires cell wall integrity (CWI) and the high osmolarity glycerol (HOG) pathways.