Fulvia fulva and Dothistroma septosporum are closely related apoplastic pathogens with similar lifestyles but different hosts: F. fulva is a pathogen of tomato, whilst D. septosporum is a pathogen of ...pine trees. In 2012, the first genome sequences of these pathogens were published, with F. fulva and D. septosporum having highly fragmented and near‐complete assemblies, respectively. Since then, significant advances have been made in unravelling their genome architectures. For instance, the genome of F. fulva has now been assembled into 14 chromosomes, 13 of which have synteny with the 14 chromosomes of D. septosporum, suggesting these pathogens are even more closely related than originally thought. Considerable advances have also been made in the identification and functional characterization of virulence factors (e.g., effector proteins and secondary metabolites) from these pathogens, thereby providing new insights into how they promote host colonization or activate plant defence responses. For example, it has now been established that effector proteins from both F. fulva and D. septosporum interact with cell‐surface immune receptors and co‐receptors to activate the plant immune system. Progress has also been made in understanding how F. fulva and D. septosporum have evolved with their host plants, whilst intensive research into pandemics of Dothistroma needle blight in the Northern Hemisphere has shed light on the origins, migration, and genetic diversity of the global D. septosporum population. In this review, we specifically summarize advances made in our understanding of the F. fulva–tomato and D. septosporum–pine pathosystems over the last 10 years.
In this review we summarize advances from the last decade in understanding the molecular basis of how the closely related fungal pathogens Fulvia fulva and Dothistroma septosporum interact with their respective tomato and pine hosts.
The Bluetongue virus serotype 8 (BTV-8) strain, which emerged in Europe in 2006, had an unusually high ability to cause foetal infection in pregnant ruminants. Other serotypes of BTV had already been ...present in Europe for more than a decade, but transplacental transmission of these strains had never been demonstrated. To determine whether transplacental transmission is a unique feature of BTV-8 we compared the incidence and pathological consequences of transplacental transmission of BTV-8 to that of BTV-1. Nine pregnant ewes were infected with either BTV-8 or BTV-1. The BTV strains used for the infection were field strains isolated on embryonated chicken eggs and passaged twice on mammalian cells. Blood samples were taken to monitor the viraemia in the ewes. Four weeks after the infection, the foetuses were examined for pathological changes and for the presence of BTV. BTV-8 could be demonstrated in 12 foetuses (43%) from 5 ewes (56%). %). BTV-1 was detected in 14 foetuses (82%) from 6 ewes (67%). Pathological changes were mainly found in the central nervous system. In the BTV-8 group, lympho-histiocytic infiltrates, gliosis and slight vacuolation of the neuropil were found. BTV-1 infection induced a severe necrotizing encephalopathy and severe meningitis, with macroscopic hydranencephaly or porencephaly in 8 foetuses. In our experimental setting, using low passaged virus strains, BTV-1 was able to induce transplacental transmission to a higher incidence compared to BTV-8, causing more severe pathology.
Coeliac disease (CD) has an estimated prevalence of ∼1% in Europe with a significant gap between undiagnosed and diagnosed CD. Active case finding may help to bridge this gap yet the diagnostic yield ...of such active case finding in general practice by serological testing is unknown.
The aim of this study was to determine (1) the frequency of diagnosed CD in the general population, and (2) to investigate the yield of active case finding by general practitioners.
Electronic medical records of 207.200 patients registered in 49 general practices in The Netherlands in 2016 were analysed. An extensive search strategy, based on International Classification of Primary Care codes, free text and diagnostic test codes was performed to search CD- or gluten-related contacts.
The incidence of CD diagnosis in general practice in 2016 was 0.01%. The prevalence of diagnosed CD reported in the general practice in the Netherlands was 0.19%, and considerably higher than previously reported in the general population. During the one year course of the study 0.95% of the population had a gluten-related contact with their GP; most of them (72%) were prompted by gastrointestinal complaints. Serological testing was performed in 66% (n = 1296) of these patients and positive in only 1.6% (n = 21).
The number of diagnosed CD patients in the Netherlands is substantially higher than previously reported. This suggests that the gap between diagnosed and undiagnosed patients is lower than generally assumed. This may explain that despite a high frequency of gluten-related consultations in general practice the diagnostic yield of case finding by serological testing is low.
Key points
The diagnostic approach of GPs regarding CD and the diagnostic yield is largely unknown
Case finding in a primary health care practice has a low yield of 1.6%
CD testing was mostly prompted by consultation for gastrointestinal symptoms
There is a heterogeneity in types of serological test performed in primary care
Soybean rust, caused by the biotrophic fungus Phakopsora pachyrhizi, is the most important foliar disease of soybean (Glycine max) worldwide. Deployment of resistant soybean cultivars is the best ...option for managing this disease. Genes conferring resistance to P. pachyrhizi have been identified, but pathotypes of the rust fungus overcoming these resistance genes have also been found. To identify novel resistance genes, soybean genotypes from both local and international sources were screened at multiple locations in Tanzania and Uganda in 2016 and 2017. The results from this screening revealed that infection types, disease severities, and sporulation levels varied among the genotypes and locations. The majority of the genotypes had tan‐coloured (TAN) lesions and developed moderate sporulation, implying susceptibility, while only seven of the 71 lines had reddish‐brown (RB) lesions and showed low disease severities in all of the screening environments. We identified seven genotypes that were the most resistant to rust in the most locations over the two years. These genotypes will be useful for further studies and, ultimately, for rust management, as they show broad resistance to various pathotypes of the rust fungus.
Various soybean genotypes were screened for resistance against the rust fungus Phakopsora pachyrhizi in Tanzania and Uganda; seven highly resistant genotypes were identified that can be employed for rust management.
Receptor-like proteins (RLPs) and receptor-like kinases (RLKs) are cell-surface receptors that are essential for detecting invading pathogens and subsequent activation of plant defense responses. ...RLPs lack a cytoplasmic kinase domain to trigger downstream signaling leading to host resistance. The RLK SOBIR1 constitutively interacts with the tomato RLP Cf-4, thereby providing Cf-4 with a kinase domain. SOBIR1 is required for Cf-4-mediated resistance to strains of the fungal tomato pathogen Cladosporium fulvum that secrete the effector Avr4. Upon perception of this effector by the Cf-4/SOBIR1 complex, the central regulatory RLK SOMATIC EMBRYOGENESIS RECEPTOR KINASE 3a (SERK3a) is recruited to the complex and defense signaling is triggered. SOBIR1 is also required for RLP-mediated resistance to bacterial, fungal ,and oomycete pathogens, and we hypothesized that SOBIR1 is targeted by effectors of such pathogens to suppress host defense responses. In this study, we show that Pseudomonas syringae pv. tomato DC3000 effector AvrPto interacts with Arabidopsis SOBIR1 and its orthologs of tomato and Nicotiana benthamiana, independent of SOBIR1 kinase activity. Interestingly, AvrPto suppresses Arabidopsis SOBIR1-induced cell death in N. benthamiana. Furthermore, AvrPto compromises Avr4-triggered cell death in Cf-4-transgenic N. benthamiana, without affecting Cf-4/SOBIR1/SERK3a complex formation. Our study shows that the RLP coreceptor SOBIR1 is targeted by a bacterial effector, which results in compromised defense responses.
The variability of stress resistance and lag time of single cells can have a big impact on their growth and therefore on the probability of their detection in food. In this study, six strains of ...Cronobacter spp. were subjected to heat, acid and desiccation stress and single cell lag times were determined using optical density measurements. The duration of lag time was highest after acid stress and did not correlate to stress resistance. The effect that the inactivation caused by stress and an extended lag time had on the projected cfu level reached after enrichment was simulated in different scenarios. For most strains, an enrichment time of 18h was sufficient for stressed cells to reach the suggested minimum level of cell inoculum for the Cronobacter screening broth detection. Particular strains may require longer recovery periods. Further, probability calculations showed that the number of samples taken from a batch may have an important effect on detection probability, especially at low contamination rates. Therefore, in addition to increasing the recovery period, increasing the number of samples is a suitable strategy to improve detection.
•Lag time was calculated from time to detection values determined from OD data.•Acid stress caused the longest lag times and desiccation stress caused the greatest inactivation.•There was no correlation of lag time and inactivation caused by heat and acid stresses.•Simulations of growth after extended lag indicated that some strains might not reach the limit of detection.•Increasing the number of samples increases the probability of detecting Cronobacter spp. in food products.
Drosera rotundifolia is a perennial insectivorous herb which occupies open, wet, oligotrophic habitats such as acidic bogs and poor fens, and specifically grows in Sphagnum-dominated communities. ...Since mediaeval times the species has been collected from natural habitats and used as a remedy for coughs and pulmonary diseases. Due to the substantial decline of Drosera habitat, the plant has been protected in most European countries since the 1980s, which means that wild D. rotundifolia has become unavailable to the pharmaceutical industry. The persistent demand has stimulated research into the cultivation of Drosera in several European countries. These studies have shown that Drosera cultivation is time-consuming and not (yet) cost-effective, and there is a need for the development of cultivation methods. This article reviews the morphology, distribution, ecology and reproduction of Drosera rotundifolia; outlines its commercial use and nature conservation requirements; and describes previous research on its propagation and cultivation.
Sphagnum farming allows sustainable and climate-friendly land use on bogs while producing a renewable substitute for peat in horticultural growing media. We studied Sphagnum productivity on an ...experimental Sphagnum culture established on a cut-over bog in Germany with strongly humified peat at the surface. Preparation of the site included levelling of the peat surface, construction of an irrigation system, spreading of Sphagnum papillosum fragments, covering them with straw, and finally rewetting. Provided there was an adequate (95 %) initial cover of Sphagnum fragments, the most relevant variables for Sphagnum productivity were found to be water supply and regular mowing of vascular plants. As long as sufficient water was supplied, the dry biomass accumulation of the established Sphagnum lawn remained high, reaching 3.7 t ha-1 yr-1 between 2007 and 2011. Annual dry Sphagnum biomass productivity over the period 2010–2011 was up to 6.9 t ha-1. During periods when high water table could not be maintained, substantial decomposition of the previously accumulated biomass occurred. After nine years the net accumulated dry mass per hectare was on average 19.5 t of pure Sphagnum and 0.7 t of subsurface vascular-plant biomass. Nitrogen deposition in the study region is apparently sufficient to support fast Sphagnum growth, whereas phosphorus and potassium may be limiting.
Summary
The Cf‐2 gene of tomato confers resistance to strains of the biotrophic pathogenic fungus Cladosporium fulvum carrying avirulence gene Avr2. To allow dissection of the biochemical mechanism ...of perception of AVR2 by Cf‐2, we set out to clone the Avr2 gene. Here, we report the functional cloning of Avr2 cDNA, based on the induction of a hypersensitive response (HR) by the encoded AVR2 protein in Cf2 tomato plants. Analysis of strains of C. fulvum that are virulent on Cf2 tomato lines revealed various independent frameshift mutations in the Avr2 open reading frame (ORF) and a point mutation resulting in a premature stop codon. All modifications result in the production of truncated AVR2 proteins. Interestingly, an additional modification involves the insertion of a LINE‐like element, Cfl1, in the Avr2 ORF. Cfl1 is the first LINE‐like element identified in C. fulvum and provides the first example of loss of avirulence of a plant pathogen caused by insertion of a retrotransposable element in an Avr gene. Rcr3 represents an additional plant protein that is specifically required for Cf‐2‐mediated resistance. Analysis of two different rcr3 mutant Cf2 tomato plants revealed that their ability to respond to AVR2 with a HR correlates with their degree of resistance to AVR2‐producing strains of C. fulvum. These data support a role for Rcr3 in the perception of AVR2 by Cf‐2.
The dictionary ‘On the meaning of words’ was written by the Roman grammarian Marcus Verrius Flaccus (ca. 55 BCE – 20 CE) but has not been preserved. A summary (“epitome”) by Sextus Pompeius Festus ...(2nd century CE), which did survive in a heavily damaged state, was in turn further epitomised by Paul the Deacon (Paulus Diaconus, 8th century CE). The work contains the intriguing peatland related phrase “famicosam terram palustrem vocabant” (‘they called marshy soils famicose’). The meaning of “famicosus” has been lost, and no other texts are known that contain the word. Grammatically, “famicosus” originates from the noun “famex” that denotes a collection of swellings of ungulate hooves. In moist and wet settings hooves tend to soften - which was well known by ancient Romans - and become prone to bacterial infections. Especially Fusobacterium necrophorum, which occurs under anaerobic conditions in wet/moist locations, causes hoof and claw diseases like interdigital dermatitis (sheep), thrush (horses) or bush rot (pigs). In combination with other bacteria like Dichelobacter nodosus or Treponema spp. even more severe hoof diseases like scald, foot rot or contagious digital dermatitis may occur (ovine/bovine). It is likely that the Romans called mires and marshes “famicose” because animals frequently developed infectious hoof diseases in these landscapes.
PDF
