Trichoderma asperellum Secreted 6-Pentyl-α-Pyrone to Control Magnaporthiopsis maydis, the Maize Late Wilt Disease Agent.

Late wilt disease (LWD) is a destructive vascular disease of maize (Zea mays L.) caused by the fungus Magnaporthiopsis maydis. Restricting the disease, which is a significant threat to commercial production in Israel, Egypt, Spain, India, and other countries, is an urgent need. In the past three years, we scanned nine Trichoderma spp. isolates as biological control candidates against M. maydis. Three of these isolates showed promising results. In vitro assays, seedlings pathogenicity trials, and field experiments all support the bio-control potential of these isolates (or their secretions). Here, a dedicated effort led to the isolation and identification of an active ingredient in the growth medium of Trichoderma asperellum (P1) with antifungal activity against M. maydis. This Trichoderma species is an endophyte isolated from LWD-susceptible maize seeds. From the chloroform extract of this fungal medium, we isolated a powerful (approx. 400 mg/L) active ingredient capable of fully inhibiting M. maydis growth. Additional purification using liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) separation steps enabled identifying the active ingredient as 6-Pentyl-α-pyrone. This compound is a potential fungicide with high efficiency against the LWD causal agent.

Galantamine Quantity and Alkaloid Profile in the Bulbs of Narcissus tazetta and daffodil cultivars (Amaryllidaceae) Grown in Israel.

Alkaloids produced by the bulbs of the Amaryllidaceae are a source of pharmaceutical compounds. The main alkaloid, galantamine, is a reversible acetylcholinesterase inhibitor and allosteric nicotinic receptor modulator, which slows cognitive and functional decline in mild to moderate dementia due to Alzheimer's disease. Having a complex stereochemistry, the organic synthesis of galantamine for pharmaceutical uses is highly challenging and not always economically viable, and it is therefore isolated from Amaryllidaceae bulbs. In the present study, galantamine was extracted and quantified in Narcissus bulbs from five cultivars (cvs.), Fortune, Carlton, Ice Follies, Galilee and Ziva, which were grown in Israel under various conditions. Results show that the cvs. Fortune, Carlton and Ice Follies bulbs contained 285 ± 47, 452 ± 73 and 69 ± 17 µg g-1 galantamine, respectively, while the Galilee and Ziva bulbs contained relatively low concentrations of galantamine (1-20 µg g-1). Irrigation levels and pruning conditions did not affect the galantamine contents. Additionally, the alkaloids profile of the five cvs. was analyzed and characterized using LC-MS/MS showing that galantamine-type alkaloids were mainly detected in the Fortune and Carlton bulbs, lycorine-type alkaloids were mainly detected at the Galilee and Ziva bulbs and vittatine-type alkaloids were mainly detected in the Ice Follies bulbs. The present research is the first to characterize the alkaloids profile in the Narcissus bulbs of Galilee and Ziva, indigenous cvs. grown in Israel. The antiviral and anticancer alkaloids lycorine and lycorinine were the main alkaloids detected in the bulbs of those cultivars.

Secretion-Based Modes of Action of Biocontrol Agents with a Focus on Pseudozyma aphidis.

Plant pathogens challenge our efforts to maximize crop production due to their ability to rapidly develop resistance to pesticides. Fungal biocontrol agents have become an important alternative to chemical fungicides, due to environmental concerns related to the latter. Here we review the complex modes of action of biocontrol agents in general and epiphytic yeasts belonging to the genus Pseudozyma specifically and P. aphidis in particular. Biocontrol agents act through multiple direct and indirect mechanisms, which are mainly based on their secretions. We discuss the direct modes of action, such as antibiosis, reactive oxygen species-producing, and cell wall-degrading enzyme secretions which can also play a role in mycoparasitism. In addition, we discuss indirect modes of action, such as hyperbiotrophy, induced resistance and growth promotion based on the secretion of effectors and elicitors from the biocontrol agent. Due to their unique characteristics, epiphytic yeasts hold great potential for use as biocontrol agents, which may be more environmentally friendly than conventional pesticides and provide a way to reduce our dependency on fungicides based on increasingly expensive fossil fuels. No less important, the complex mode of action of Pseudozyma-based biocontrol agents can also reduce the frequency of resistance developed by pathogens to these agents.

Pseudozyma aphidis activates reactive oxygen species production, programmed cell death and morphological alterations in the necrotrophic fungus Botrytis cinerea.

Many types of yeast have been studied in the last few years as potential biocontrol agents against different phytopathogenic fungi. Their ability to control plant diseases is mainly through combined modes of action. Among them, antibiosis, competition for nutrients and niches, induction of systemic resistance in plants and mycoparasitism have been the most studied. In previous work, we have established that the epiphytic yeast Pseudozyma aphidis inhibits Botrytis cinerea through induced resistance and antibiosis. Here, we demonstrate that P. aphidis adheres to B. cinerea hyphae and competes with them for nutrients. We further show that the secreted antifungal compounds activate the production of reactive oxygen species and programmed cell death in B. cinerea mycelium. Finally, P. aphidis and its secreted compounds negatively affect B. cinerea hyphae, leading to morphological alterations, including hyphal curliness, vacuolization and branching, which presumably affects the colonization ability and infectivity of B. cinerea. This study demonstrates additional modes of action for P. aphidis and its antifungal compounds against the plant pathogen B. cinerea.

Biological control of the cucurbit powdery mildew pathogen Podosphaera xanthii by means of the epiphytic fungus Pseudozyma aphidis and parasitism as a mode of action.

Epiphytic yeasts, which colonize plant surfaces, may possess activity that can be harnessed to help plants defend themselves against various pathogens. Due to their unique characteristics, epiphytic yeasts belonging to the genus Pseudozyma hold great potential for use as biocontrol agents. We identified a unique, biologically active isolate of the epiphytic yeast Pseudozyma aphidis that is capable of inhibiting Botrytis cinerea via a dual mode of action, namely induced resistance and antibiosis. Here, we show that strain L12 of P. aphidis can reduce the severity of powdery mildew caused by Podosphaera xanthii on cucumber plants with an efficacy of 75%. Confocal and scanning electron microscopy analyses demonstrated P. aphidis proliferation on infected tissue and its production of long hyphae that parasitize the powdery mildew hyphae and spores as an ectoparasite. We also show that crude extract of P. aphidis metabolites can inhibit P. xanthii spore germination in planta. Our results suggest that in addition to its antibiosis as mode of action, P. aphidis may also act as an ectoparasite on P. xanthii. These results indicate that P. aphidis strain L12 has the potential to control powdery mildew.

Coffee polyphenols protect human plasma from postprandial carbonyl modifications.

The antioxidant capability of coffee polyphenols to inhibit red-meat lipid peroxidation in stomach medium and absorption into blood of malondialdehyde (MDA) in humans was studied. Roasted-ground coffee polyphenols that were found to inhibit lipid peroxidation in stomach medium are 2- to 5-fold more efficient antioxidant than those found in instant coffee. Human plasma from ten volunteers analyzed after a meal of red-meat cutlets (250 g) revealed a rapid accumulation of MDA. The accumulation of MDA in human plasma modified low-density lipoprotein is known to trigger atherogenesis. Consumption of 200 mL roasted coffee by ten volunteers during a meal of red-meat cutlets, resulted after 2 and 4 h in the inhibition by 80 and 50%, respectively, of postprandial plasma MDA absorption. The results obtained in vitro simulated stomach model on MDA accumulation were predictive for the amount of MDA absorbed into circulating human plasma, in vivo. Timing the consumption of coffee during the meals may make it a very active functional food.

Hydrogen peroxide photocycling in the Gulf of Aqaba, Red Sea.

The dynamics of hydrogen peroxide (H(2)O(2)) was investigated from December 2007 to October 2008 in the Gulf of Aqaba, which in the absence of H(2)O(2) contribution from biological production, rain and runoff, turned out to be a unique natural photochemical laboratory. A distinct seasonal pattern emerged, with highest midday surface H(2)O(2) concentrations in spring-summer (30-90 nM) as compared to winter (10-30 nM). Similarly, irradiation normalized net H(2)O(2) formation rates obtained in concurrent ship-board experiments were faster in spring-summer than in winter. These seasonal patterns were attributed to changes in water characteristics, namely elevated spring-summer chromophoric dissolved organic matter (CDOM). The role of trace elements in H(2)O(2) photoformation was studied by simultaneously measuring superoxide (O(2)(-)), Fe(II), and H(2)O(2) formation and loss in ambient seawater and in the presence of superoxide dismutase, iron and copper. O(2)(-) was found to decay fast in the Gulf water, with a half-life of 15-28 s, primarily due to catalytic reactions with trace metals (predominantly copper). Hence, H(2)O(2) formation in the Gulf involves metal-catalyzed O(2)(-) disproptionation. Added iron moderately lowered net H(2)O(2) photoformation, probably due to its participation in Fe(II) oxidation, a process that may also modify H(2)O(2) formation in situ.