Tramesan elicits durum wheat defense against the septoria disease complex

The Septoria Leaf Blotch Complex (SLBC), caused by the two ascomycetes Zymoseptoria tritici and Parastagonospora nodorum, can reduce wheat global yearly yield by up to 50%. In the last decade, SLBC incidence has increased in Italy; notably, durum wheat has proven to be more susceptible than common wheat. Field fungicide treatment can efficiently control these pathogens, but it leads to the emergence of resistant strains and adversely affects human and animal health and the environment. Our previous studies indicated that active compounds produced by Trametes versicolor can restrict the growth of mycotoxigenic fungi and the biosynthesis of their secondary metabolites (e.g., mycotoxins). Specifically, we identified Tramesan: a 23 kDa α-heteropolysaccharide secreted by T. versicolor that acts as a pro-antioxidant molecule in animal cells, fungi, and plants. Foliar-spray of Tramesan (3.3 μM) on SLBC-susceptible durum wheat cultivars, before inoculation of causal agents of Stagonospora Nodorum Blotch (SNB) and Septoria Tritici Blotch (STB), significantly decreased disease incidence both in controlled conditions (SNB: –99%, STB: –75%) and field assays (SNB: –25%, STB: –30%). We conducted these tests were conducted under controlled conditions as well as in field. We showed that Tramesan increased the levels of jasmonic acid (JA), a plant defense-related hormone. Tramesan also increased the early expression (24 hours after inoculation-hai) of plant defense genes such as PR4 for SNB infected plants, and RBOH, PR1, and PR9 for STB infected plants. These results suggest that Tramesan protects wheat by eliciting plant defenses, since it has no direct fungicidal activity. In field experiments, the yield of durum wheat plants treated with Tramesan was similar to that of healthy untreated plots. These results encourage the use of Tramesan to protect durum wheat against SLBC

Communication with plants

During plant-fungal interaction a wide range of molecules play crucial roles in signaling, development and stress response. Understand the fungal and plant cross-talk allows to define the typology of interaction or rather the lifestyle. According to this we can distinguish in biotrophs, necrotrophs or hemibiotrophs fungi. In any case, during the interaction the perception of signals activates signal transduction processes that induce changes in metabolism, cell organization and gene expression, here we review the concept of chemotropism, the ability to sense and grow towards a chemical gradient. When the host recognizes a pathogenic fungus, it can active the defense responses. However the pathogen can bypass them, by expressing or secreting molecules effectors that can modulate the plant immune system to their own advantage. Among the signals that the pathogenic fungus can produce, lipids represent a class of particular interest. In the article are reported several examples of lipids involved in the communication, in particular fatty acids, oxylipins (oxidized fatty acids) and sphingolipids. In addition, during fungus-host interaction, the fungus can influence its virulence by activating the production of mycotoxins, secondary metabolites that can influence the outcome of interaction. Our aim in this review is to describe the state of art of host-pathogen interaction, to better understand the communication during plant-fungus interaction, for that purpose some signal molecules will be brought to light involved in interactions

Use of the secreted proteome of Trametes versicolor for controlling the cereal pathogen Fusarium langsethiae

Fusarium langsethiae is amongst the most recently discovered pathogens of small grains cereals. F. langsethiae is the main producer, in Europe, of T2 and HT-toxins in small grain cereals, albeit often asymptomatic; this makes its control challenging. The European Union (EU) is pushing hard on the use of biocontrol agents to minimize the use of fungicides and pesticides, which are detrimental to the environment and responsible for serious pollution of the soil and superficial water. In line with EU directives (e.g., 128/2009), here we report the use of protein fractions, purified from the culture filtrate of the basidiomycete Trametes versicolor, for controlling F. langsethiae. T. versicolor, a so-called medicinal mushroom which is applied as a co-adjuvant in oncology and other pathologies as a producer of biological response modifiers. In this study, the exo-proteome of T. versicolor proved highly efficient in inhibiting the growth of F. langsethiae and the biosynthesis of the T2 toxin. Results are promising for its future use as a sustainable product to control F. langsethiae infection in cereals under field conditions

Light-stress response mediated by the transcription factor KlMga2 in the yeast Kluyveromyces lactis

In unicellular organisms like yeasts, which do not have specialized tissues for protection against environmental challenges, the presence of cellular mechanisms to respond and adapt to stress conditions is fundamental. In this work, we aimed to investigate the response to environmental light in Kluyveromyces lactis. Yeast lacks specialized light-sensing proteins; however, Saccharomyces cerevisiae has been reported to respond to light by increasing hydrogen peroxide level and triggering nuclear translocation of Msn2. This is a stress-sensitive transcription factor also present in K. lactis. To investigate light response in this yeast, we analyzed the different phenotypes generated by the deletion of the hypoxia responsive and lipid biosynthesis transcription factor KlMga2. Alterations in growth rate, mitochondrial functioning, ROS metabolism, and fatty acid biosynthesis provide evidence that light was a source of stress in K. lactis and that KlMga2 had a role in the light-stress response. The involvement of KlMsn2 and KlCrz1 in light stress was also explored, but the latter showed no function in this response

The Crz1 transcription factor regulates lipid metabolism and fumonisin production in Fusarium verticillioides

Calcineurin, a key player in calcium-dependent signal transduction pathways of eukaryotes, modulates colony growth, stress response and pathogenicity in fungi (Thewes, 2014). Here we investigated the role of the fungal protein Crz1, a downstream transcription factor of the calcineurin pathway, in the fumonisin-producing fungus Fusarium verticillioides. Previous studies have shown that the production of fumonisins in Fusarium is related to the presence in the growth medium of some specific fatty acids (FAs) and oxylipins (i.e. oxidized FAs) which are released by both the plant and the fungus, and that play pivotal functions in the crosstalk between host and pathogens (Dall'Asta et al., 2012; Scala et al., 2014). In this study, we report the involvement of Crz1 in the regulation of both lipid metabolism and fumonisin production during the F. verticillioides-maize interaction. F. verticillioides crz1Δ strains showed higher membrane permeability and susceptibility to ionic stress when compared to the wild type or the crz1Δ+crz1 complemented strains. Through a mass spectrometry approach, we also found that the deletion of crz1 was consistently associated with an overall reduction in oxylipin, FA and mycotoxin content during maize infection. We postulate that Crz1 is required for the proper generation of signalling lipid molecules (e.g. FAs or oxylipins) which in turn activate fumonisin biosynthesis in F. verticillioides

Volatilome and proteome responses to Colletotrichum lindemuthianum infection in a moderately resistant and a susceptible bean genotype

We analyzed the changes in the volatilome, proteome, stomatal conductance, salicylic and jasmonic acid contents of a susceptible and a moderately resistant genotype of common bean, Phaseoulus vulgaris L., challenged with Colletotrichum lindemuthianum, the causal agent of fungal anthracnose. Our results indicate differences at both proteome and volatilome levels between the two genotypes, before and after the infection, and different defense strategies. The moderately resistant genotype hindered pathogen infection, invasion, and replication mainly by maintaining epidermal and cell wall structure. The susceptible genotype was not able to limit the early stages of pathogen infection. Rather, stomatal conductance increased in the infected susceptible genotype, and enhanced synthesis of Green Leaf Volatiles and salicylic acid was observed, together with a strong hypersensitive response. Proteomic investigation provided a general framework for physiological changes, whereas observed variations in the volatilome suggested that volatile organic compounds may principally represent stress markers rather than defensive compounds per se

The effect of Fusarium verticillioides fumonisins on fatty acids, sphingolipids, and oxylipins in maize germlings

Fusarium verticillioides causes multiple diseases of Zea mays (maize) including ear and seedling rots, contaminates seeds and seed products worldwide with toxic chemicals called fumonisins. The role of fumonisins in disease is unclear because, although they are not required for ear rot, they are required for seedling diseases. Disease symptoms may be due to the ability of fumonisins to inhibit ceramide synthase activity, the expected cause of lipids (fatty acids, oxylipins, and sphin-golipids) alteration in infected plants. In this study, we explored the impact of fumonisins on fatty acid, oxylipin, and sphingolipid levels in planta and how these changes affect F. verticillioides growth in maize. The identity and levels of principal fatty acids, oxylipins, and over 50 sphingolipids were evaluated by chromatography followed by mass spectrometry in maize infected with an F. verticillioides fumonisin-producing wild-type strain and a fumonisin-deficient mutant, after different periods of growth. Plant hormones associated with defense responses, i.e., salicylic and jasmonic acid, were also evaluated. We suggest that fumonisins produced by F. verticillioides alter maize lipid metabolism, which help switch fungal growth from a relatively harmless endophyte to a destructive necrotroph

Analysis of the expression of genes related to oxylipin biosynthesis in Fusarium verticillioides and maize kernels during their interaction

Fusarium verticillioides is a pathogen that can cause ear and stalk rot in maize. Under suitable environmental conditions, this fungus produces large amount of fumonisins, a potential carcinogenic to humans and animals classified as IARC2B. Recent studies have shown that pathogen and host exchange an oxylipin-based cross talk during their interaction. This study was aimed at investigating whether environmental conditions, namely water activity (a(w)) at 0.90 and 20 degrees C, which are the thresholds for F. verticillioides development, affect the maize/fungal oxylipin gene expression profile. Fungal Fvlds1-3, Fvlox, Zmlox3 and the maize defense-related ZmPR1 genes significantly changed their expression after infection at 0.90 a(w) and 20 degrees C. Moreover, the expression of maize genes peaked after that of fungal genes, indicating that, under these experimental conditions, plant and pathogen coordinate the oxylipin gene expression reciprocally. This kind of modulation of fungal and plant gene expression is suggestive of the "zig zag model" proposed for other plant-pathogen interaction systems

A multi-species bunch of VIM-1 Carbapenemase producing enterobacterales linked by a novel, highly conjugative and broad-host range IncA plasmid, menaces the re-emergence of VIM-1

In this study we investigated VIM-1-producing Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Citrobacter freundii, and Enterobacter cloacae strains, isolated in 2019 during a period of active surveillance of carbapenem resistant Enterobacterales in a large university hospital in Italy. VIM-1-producing strains colonized the gut of patients, with up to three different VIM-1-positive bacterial species isolated from a single rectal swab, but also caused bloodstream infection to one colonized patient. In the multi-species cluster the bla VIM-1 was identified in a 5-gene cassette class 1 integron, associated with several genetic determinants, including the bla SHV-12, qnrS1 and mph(A) genes, located on a highly conjugative and broad-host range IncA plasmid. Characteristics and origin of this IncA plasmid were studied