Hormetic doses of UV-C light decrease the susceptibility of tomato plants to Botrytis cinerea infection

Preharvest hormetic doses of UV-C radiation can decrease the susceptibility of tomato leaves to Botrytis cinerea L. infection. UV-C light treatments have been shown to be very effective for reducing disease development in several species, including tomato (Solanum lycopersicum L.). Treating cultivated tomato plants with UV-C light is of interest not only because of the disinfecting effects of UV-C light but also because of its ability to stimulate plant defences (SDP) against diseases, provided that the applied doses are high enough to be effective while low enough to prevent deleterious effects. In the present study, the effects of UV-C light on plants were evaluated by biochemical analyses, including analyses of the activities of antioxidant enzymes and phenylalanine lyase (PAL); the concentration of malondialdehyde (MDA), an indicator of membrane integrity; and chlorophyll fluorescence parameters, such as the maximum quantum efficiency of photosystem II (F_V/F_M) and the Strasser performance index (PI). In this work, treatments with single doses of 0.85 kJ/m² of UV-C light were found to significantly increase plant defences against B. cinerea, reducing the affected leaf area by 51% compared to the affected area of control plants. This decrease in susceptibility was associated with increased PAL activity and the amount of bound phenolics compared to levels in control plants (not treated with UV-C).     

Conservation and expansion of a necrosis-inducing small secreted protein family from host-variable phytopathogens of the Sclerotiniaceae

Fungal effector proteins facilitate host-plant colonization and have generally been characterized as small secreted proteins (SSPs). We classified and functionally tested SSPs from the secretomes of three closely related necrotrophic phytopathogens: Ciborinia camelliae, Botrytis cinerea, and Sclerotinia sclerotiorum. Alignment of predicted SSPs identified a large protein family that share greater than 41% amino acid identity and that have key characteristics of previously described microbe-associated molecular patterns (MAMPs). Strikingly, 73 of the 75 SSP family members were predicted within the secretome of the host-specialist C. camelliae with single-copy homologs identified in the secretomes of the host generalists S. sclerotiorum and B. cinerea. To explore the potential function of this family of SSPs, 10 of the 73 C. camelliae proteins, together with the single-copy homologs from S. sclerotiorum (SsSSP3) and B. cinerea (BcSSP2), were cloned and expressed as recombinant proteins. Infiltration of SsSSP3 and BcSSP2 into host tissue induced rapid necrosis. In contrast, only one of the 10 tested C. camelliae SSPs was able to induce a limited amount of necrosis. Analysis of chimeric proteins consisting of domains from both a necrosis-inducing and a non-necrosis-inducing SSP demonstrated that the C-terminus of the S. sclerotiorum SSP is essential for necrosis-inducing function. Deletion of the BcSSP2 homolog from B. cinerea did not affect growth or pathogenesis. Thus, this research uncovered a family of highly conserved SSPs present in diverse ascomycetes that exhibit contrasting necrosis-inducing functions.     

Rapid molecular technique for identification of a biological control agent Rhodosporidium diobovatum

The purpose of this study was to develop a rapid molecular technique for identification of the biological control agent, Rhodosporidium diobovatum. DNA from all yeast cultures described below was extracted, amplified by PCR using primers specific to septate fungi, and fixed to nylon membranes. Using sequence information obtained from the GenBank database, Rhodosporidium diobovatum-specific oligonucleotides were designed and, after labeling with digoxigenin-d-UTP, were used as probes in a dot-blot hybridization assay. After preliminary testing, two probes were selected for further study. For probe RD3, a positive reaction was obtained at 38, 42 and 48°C with R. diobovatum in pure culture. Other yeast isolates such as Rhodosporidium toruloides, R. fluviale, R. babjevae, R. sphaerocarpum, R. kratochvilovae, R. azoricum, Pichia anomala, and some common greenhouse pathogens tested gave a negative result. The other probe (RD1) reacted with two species, R. diobovatum and R. babjevae at 42°C. The present dot-blot assay can be used reliably to identify the biocontrol agent, Rhodosporidium diobovatum, from pure culture and plant tissue.     

Two New Furanoeremophilanes from Senecio santelisis

From an Argentine collection of Senecio santelisis Phil ., the new furanoeremophilanoids, (10βH)‐6β‐acetoxy‐1α‐hydroxyfuranoeremophilan‐9‐one ( 1 ) and (10βH)‐1α‐hydroxy‐6β‐(propanoyloxy)furanoeremophilan‐9‐one ( 2 ), together with the known (10αH)‐6β‐acetoxy‐1α‐hydroxyfuranoeremophilan‐9‐one ( 3 ), (10αH)‐1α,6β‐diacetoxyfuranoeremophilan‐9‐one ( 4 ), and (10αH)‐1α‐hydroxy‐6β‐(propanoyloxy)furanoeremophilan‐9‐one ( 5 ) were isolated. Their structures and relative configurations were established on the basis of spectroscopic analysis. CHCl₃ Extract and pure compounds were evaluated for their antifungal activity. Compound 5 exhibited remarkable mycelial growth inhibition against B. cinerea with an IC₅₀ value of 21.4 μg/ml.     

2‐DE proteomic approach to the Botrytis cinerea secretome induced with different carbon sources and plant‐based elicitors

Botrytis cinerea is a phytopathogenic fungus infecting a number of crops (tomatoes, grapes and strawberries), which has been adopted as a model system in molecular phytopathology. B. cinerea uses a wide variety of infection strategies, which are mediated by a set of genes/proteins called pathogenicity/virulence factors. Many of these factors have been described as secreted proteins, and thus the study of this sub‐proteome, the secretome, under changing circumstances can help us to understand the roles of these factors, possibly revealing new loci for the fight against the pathogen. A 2‐DE, MALDI TOF/TOF‐based approach has been developed to establish the proteins secreted to culture media supplemented with different carbon sources and plant‐based elicitors (in this study: glucose, cellulose, starch, pectin and tomato cell walls). Secreted proteins were obtained from the culture media by deoxycholate‐trichloroacetic acid/phenol extraction, and 76 spots were identified, yielding 95 positive hits that correspond to 56 unique proteins, including several known virulence factors (i.e. pectin methyl esterases, xylanases and proteases). The observed increases in secretion of proteins with established virulence‐related functions indicate that this in vitro‐induction/proteome‐mining approach is a promising strategy for discovering new pathogenicity factors and dissecting infection mechanisms in a discrete fashion.     

Biological control of grey mould in strawberry fruits by halophilic bacteria

Aims:  Grey mould caused by Botrytis cinerea is an economically important disease of strawberries in Tunisia and worldwide. The aim of this study was to select effective halophilic bacteria from hypersaline ecosystems and evaluate the abilities of antifungal bacteria to secrete extracellular hydrolytic enzymes, anti- Botrytis metabolites and volatiles.
Methods and Results:  Grey mould was reduced in strawberry fruits treated with halophilic antagonists and artificially inoculated with B. cinerea . Thirty strains (20·2%) were active against the pathogen and reduced the percentage of fruits infected after 3 days of storage at 20°C, from 50% to 91·66%. The antagonists were characterized by phenotypic tests and 16S rDNA sequencing. They were identified as belonging to one of the species: Virgibacillus marismortui , B. subtilis , B. pumilus , B. licheniformis , Terribacillus halophilus , Halomonas elongata , Planococcus rifietoensis , Staphylococcus equorum and Staphylococcus sp. The effective isolates were tested for antifungal secondary metabolites.
Conclusions:  Moderately halophilic bacteria may be useful in biological control against this pathogen during postharvest storage of strawberries.
Significance and Impact of the study:  The use of such bacteria may constitute an important alternative to synthetic fungicides. These moderate halophiles can be exploited in commercial production and application of the effective strains under storage and greenhouse conditions.     

Chemical constituents of the fermented broth of the ascomycete Theissenia cinerea 89091602

One new betaenone, theissenoic acid (1), together with three new acetogenins, theissenolactones A-C (2-4, resp.), were isolated from the fermented broth of Theissenia cinerea 89091602 isolated in Taiwan. The structures of 1-4 were elucidated by spectroscopic methods. Biological tests revealed that 3 and 4 exhibited moderate growth-inhibitory activities against A549 lung cancer cell line with GI(50) values of 14.9 and 47.9 μM, respectively.