Enzymatic component of antioxidative system in succulent plant Tacitus bellus as a response to hemibiotroph Fusarium verticillioides infection in vitro

Fungi and plants interact in different ways, creating a scale of associations. Hemibiotrophic fungi represent the most interesting group, as they use sequential biotrophic and necrotrophic infection strategies. The co-evolution of plant and fungal life-styles has not been well characterized. We present changes of enzymatic component of antioxidative system in succulent plant Tacitus bellus that specifically correspond to subsequent phases (spore germination, biotrophic phase, and necrotrophic phase) of hemibiotroph Fusarium verticillioides infection. T. bellus response to F. verticillioides spore germination was characterized by transient increase in catalase (CAT), but decrease in superoxide dismutase (SOD) and peroxidase (POD) activity. During biotrophic phase of F. verticillioides infection, when hyphae spread intercellularly in epidermal and mesophyll tissue, host antioxidative system was suppressed. The transition from biotrophic to necrotrophic phase (inter and intracellular colonization and sporulation) triggered the host plant cells to create a highly defensive environment: CAT, SOD and POD activities were significantly stimulated, slowing, or even currently arresting, colonization of T. bellus mesophyll cells. CAT, showing the most pronounced activity increase, could be suggested as the main enzyme responsible for slowing the progression of necrotrophic phase of F. verticillioides growth. However, contrary to host CAT and SOD which isoenzyme profile didn’t change, new highly acidic POD isoforms replaced the two mildly acidic isoforms, suggesting their specific role in slowing the progression of infection. Presented results add to knowledge of events and mechanisms related to hemibiotrophic fungi pathogenicity in succulent plants grown under high relative humidity, similar to conditions in greenhouse

Efekti selenita na metabolizam glutationa kod gljive Phycomyces blakesleeanus

Elementarni selen je najmanje biotoksičan oblik selena u prirodi, dok selen-oksianjoni mogu biti toksični zbog značajne pokretljivosti i rastvorljivosti u vodi. Mikrobiološka redukcija selena +4 (selenit) u elementarni selen je stoga od presudnog značaja za smanjenje bioraspoloživosti ovog elementa.1 Visoka reaktivnost selen-oksianjona sa tiolnim grupama, kao i formiranje kiseoničnih radikala u reakciji sa glutationom implicira da oksidativni stres doprinosi toksičnosti selena.2 Tokom biološke redukcije selenita se proizvodi velika količina peroksida čime se indukuje ekspresija gena koji kodiraju enzime antioksidativnog metabolizma, što uključuje i enzime metabolizma glutationa.1 Micelijum gljive Phycomyces blakesleeanus star 24 sata je tretiran 10 mM rastvorom selenita. Uzorci su nakon određenih vremenskih intervala (1, 5, 10, 30, 60 minuta, 24 i 96 sati) ispirani i homogenizovani, nakon čega je meren sadržaj glutationa i specifična aktivnost enzima: peroksidaza (POD), katalaza (CAT), superoksid dismutaza (SOD), glutation peroksidaze (GPx), glutation-S-transferaze (GST) i glutation reduktaze (GR). Nakon dodavanja selenita utvrđen je pad količine ukupnog glutationa u micelijumu. Aktivnost POD i SOD je rasla do 60 minuta, nakon čega je opadala. Aktivnost CAT opadala je odmah po dodatku selenita. Najizraženija je bila promena aktivnosti GPx gde je zabeležen značajan porast, dok su promene aktivnosti GST i GR bile manje izražen

SELENITE METABOLISM IN THE MYCELIUM OF THE FUNGUS PHYCOMYCES BLAKESLEEANUS

In this study, mycelium of fungus Phycomyces blakesleeanus was exposed to soluble toxic form of selenium, selenite (Se+4), with the aim of determining the flow and products of its biotransformation. Selenite is reduced to Se0 in the form selenium nanoparticles (SeNPs) and Se-2 in the form of methylated volatile selenides. Low concentrations of Se+4 in the mycelium form RSSeSR type compounds, which could be a step in the process of SeNPs formation, or incorporation of Se into metabolites such as Se-amino acids

PRODUCTION AND CHARACTERISATION OF SELENIUM NANOPARTICLES BY MYCELIUM OF FUNGUS PHYCOMYCES BLAKESLEEANUS

In this study, mycelium of fungus Phycomyces blakesleeanus was exposed to soluble toxic form of selenium, selenite (Se+4), to examine its ability to reduce it to nanoparticles. Red coloration appeared after only a few hours of incubation with 10 mM Se+4 indicating formation of selenium nanoparticles (SeNPs). SEM-EDS confirmed pure selenium NPs with an average diameter of 57 nm, which indicates to potentially very good medical, optical and photoelectric characteristics. Raman spectroscopy showed several structural forms of SeNPs formed in the extracellular space with a monoclinic Se8 chain as the most represented, and the other observed forms were trigonal Se polymer chain, Se8 ring and Se6 chain structures