The tomato saponin a-tomatine has been proposed to kill sensitive cells by binding to cell membranes followed by leakage of cell components. However, details of the modes of action of the compound on fungal cells are poorly understood. In the present study, mechanisms involved in a-tomatine-induced cell death of fungi were examined using a filamentous pathogenic fungus Fusarium oxysporum. a-Tomatine-induced cell death of F. oxysporum (TICDF) occurred only under aerobic conditions and was blocked by the mitochondrial F 0 F 1 -ATPase inhibitor oligomycin, the caspase inhibitor D-VAD-fmk, and protein synthesis inhibitor cycloheximide. Fungal cells exposed to a-tomatine showed TUNEL-positive nuclei, depolarization of transmembrane potential of mitochondria, and reactive oxygen species (ROS) accumulation. These results suggest that TICDF occurs through a programmed cell death process in which mitochondria play a pivotal role. Pharmacological studies using inhibitors suggest that a-tomatine activates phosphotyrosine kinase and monomeric G-protein signaling pathways leading to Ca 2+ elevation and ROS burst in F. oxysporum cells.

Trichoderma spp. are versatile opportunistic plant symbionts that can cause substantial changes in the metabolism of host plants, thereby increasing plant growth and activating plant defense to various diseases. Target metabolite profiling approach was selected to demonstrate that Trichoderma longibrachiatum isolated from desert soil can confer beneficial agronomic traits to onion and induce defense mechanism against Fusarium oxysporum f. sp. cepa (FOC), through triggering a number of primary and secondary metabolite pathways. Onion seeds primed with Trichoderma T1 strain displayed early seedling emergence and enhanced growth compared with Trichoderma T2-treatment and untreated control. Therefore, T1 was selected for further investigations under greenhouse conditions, which revealed remarkable improvement in the onion bulb growth parameters and resistance against FOC. The metabolite platform of T1-primed onion (T1) and T1-primed onion challenged with FOC (T1+FOC) displayed significant accumulation of 25 abiotic and biotic stress-responsive metabolites, representing carbohydrate, phenylpropanoid and sulfur assimilation metabolic pathways. In addition, T1- and T1+FOC-treated onion plants showed discrete antioxidant capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) compared with control. Our findings demonstrated the contribution of T. longibrachiatum to the accumulation of key metabolites, which subsequently leads to the improvement of onion growth, as well as its resistance to oxidative stress and FOC.

Phytochemical analysis of the methanolic and aqueous extracts of Faidherbia albida legumes indicated the presence of terpenes, cardiac glycosides, monosaccharides and carbohydrates type of compounds in both extracts. While alkaloids and saponins were found in aqueous extract only, flavonoids were found to be absent in both extracts. The aqueous and methanolic extracts exhibited a potent growth stimulation effect. Inhibition of both the rootlet and shoot showed a dose dependent response. Aqueous extract has a greater inhibitory effect on rootlet growth than shoot growth. The methanolic extract has a greater inhibitory effect than the aqueous extract. Both extracts and some fractions were tested against three pathogenic bacterial species; Staphylococcus aureus, Escherichia coli and Shigella dysenteriae, also tested against three pathogenic fungal species; Fusarium oxysporum, Alternaria alternate, and Aspergillus niger. Most of the plant extracts stimulate the studied fungal growth specially the aqueous extract. Meanwhile it shows interesting results by inhibiting the growth of the studied pathogenic bacterial species with most extracts and fractions

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