Nitrogen Nutrition Modulates the Response to Infection via Metabolic Modifications in Seedlings.

Little is known about the effect of nitrogen nutrition on seedling susceptibility to seed-borne pathogens. We have previously shown that seedlings grown under high nitrate (5 mM) conditions are less susceptible than those grown under low nitrate (0.1 mM) and ammonium (5 mM) in the Arabidopsis- pathosystem.

It is buzziness time: rearing, mating, and overwintering Bombus vosnesenskii (Hymenoptera: Apidae).

Bombus vosnesenskii Radowszkowski, 1862 is one of three bumble bee species commercially available for pollination services in North America; however, little is documented about B. vosnesenskii colony life cycle or the establishment of ex situ rearing, mating, and overwintering practices. In this study, we documented nest success, colony size, and gyne production; recorded the duration of mating events; assessed overwintering survival of mated gynes; and evaluated second-generation nest success for colonies established from low- and high-elevation wild-caught B.

Sperm can't take the heat: Short-term temperature exposures compromise fertility of male bumble bees (Bombus impatiens).

Bumble bee (genus Bombus) populations are increasingly under threat from habitat fragmentation, pesticides, pathogens, and climate change. Climate change is likely a prime driver of bumble bee declines but the mechanisms by which changing climates alter local abundance, leading to shifts in geographic range are unclear. Heat tolerance is quite high in worker bumble bees (CT ∼ 48-55 °C), making it unlikely for them to experience these high temperatures, even with climate warming.

A new in vitro monitoring system reveals a specific influence of Arabidopsis nitrogen nutrition on its susceptibility to Alternaria brassicicola at the seedling stage.

Background: Seedling growth is an early phase of plant development highly susceptible to environmental factors such as soil nitrogen (N) availability or presence of seed-borne pathogens. Whereas N plays a central role in plant-pathogen interactions, its role has never been studied during this early phase for the interaction between Arabidopsis thaliana and Alternaria brassicicola, a seed-transmitted necrotrophic fungus. The aim of the present work was to develop an in vitro monitoring system allowing to study the impact of the fungus on A.

Seed Transmission of Pathogens: Non-Canonical Immune Response in Germinating Seeds Compared to Early Seedlings against the Necrotrophic Fungus .

The transmission of seed-borne pathogens by the germinating seed is responsible for major crop diseases. The immune responses of the seed facing biotic invaders are poorly documented so far. The / patho-system was used to describe at the transcription level the responses of germinating seeds and young seedling stages to infection by the necrotrophic fungus.

Development of a quantification method for routine analysis of glucosinolates and camalexin in brassicaceous small-sized samples by simultaneous extraction prior to liquid chromatography determination.

Glucosinolates and camalexin are secondary metabolites that, as phytoanticipins and phytoalexins, play a crucial role in plant defence. The present work proposes an improved analytical method for routine analysis and quantification of glucosinolates and camalexin in brassicaceous small-sized samples by using the very specific desulfation process of glucosinolates analysis and the specificity of fluorescence detection for camalexin analysis. The approach is based on a simultaneous ultrasound-assisted extraction followed by a purification on an anion-exchange column.

Nitrogen nutrition modifies the susceptibility of Arabidopsis thaliana to the necrotrophic fungus, Alternaria brassicicola.

The impact of the form of nitrogen (N) source (nitrate versus ammonium) on the susceptibility to Alternaria brassicicola, a necrotrophic fungus, has been examined in Arabidopsis thaliana at the rosette stage. Nitrate nutrition was found to increase fungal lesions considerably. There was a similar induction of defence gene expression following infection under both N nutritions, except for the phytoalexin deficient 3 gene, which was overexpressed with nitrate.

Cryopreservation of seminal vesicle derived spermatozoa from Bombus impatiens and Apis mellifera - Implications for artificial insemination of bumble bees.

This study evaluates the efficacy of a cryopreservation protocol for spermatozoa derived from the accessory testis of male Bombus impatiens. It is also the first report of successful cryopreservation of bumble bee spermatozoa. The spermatozoa viability was compared with the similarly treated honey bee spermatozoa derived from its accessory testis.

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.

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.

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.

Phenoplant: a web resource for the exploration of large chlorophyll fluorescence image datasets.

Background: Image analysis is increasingly used in plant phenotyping. Among the various imaging techniques that can be used in plant phenotyping, chlorophyll fluorescence imaging allows imaging of the impact of biotic or abiotic stresses on leaves. Numerous chlorophyll fluorescence parameters may be measured or calculated, but only a few can produce a contrast in a given condition.

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.

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.

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.

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.

The group III two-component histidine kinase of filamentous fungi is involved in the fungicidal activity of the bacterial polyketide ambruticin.

We have shown that the plant pathogen Alternaria brassicicola exhibited very high susceptibility to ambruticin VS4 and to a lesser extent to the phenylpyrrole fungicide fludioxonil. These compounds are both derived from natural bacterial metabolites with antifungal properties and are thought to exert their toxicity by interfering with osmoregulation in filamentous fungi. Disruption of the osmosensor group III histidine kinase gene AbNIK1 (for A.

Characterization of AgMaT2, a plasma membrane mannitol transporter from celery, expressed in phloem cells, including phloem parenchyma cells.

A second mannitol transporter, AgMaT2, was identified in celery (Apium graveolens L. var. dulce), a species that synthesizes and transports mannitol.

Ha-DEF1, a sunflower defensin, induces cell death in Orobanche parasitic plants.

Plant defensins are small basic peptides of 5-10 kDa and most of them exhibit antifungal activity. In a sunflower resistant to broomrape, among the three defensin encoding cDNA identified, SF18, SD2 and HaDef1, only HaDef1 presented a preferential root expression pattern and was induced upon infection by the root parasitic plant Orobanche cumana. The amino acid sequence deduced from HaDef1 coding sequence was composed of an endoplasmic reticulum signal sequence of 28 amino acids, a standard defensin domain of 50 amino-acid residues and an unusual C-terminal domain of 30 amino acids with a net positive charge.