Department of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, St. Paul, MN 55108, USA.
Fungal Genet Biol. 2011 Sep;48(9):874-85. doi: 10.1016/j.fgb.2011.06.006. Epub 2011 Jun 15.
The goal of this research was to determine mechanisms of interaction between endophytic strains of Fusarium verticillioides (Sacc.) Nirenberg and the pathogen, Ustilago maydis (DC) (Corda). Endophytic strains of the fungus F. verticillioides are commonly found in association with maize (Zea mays) and when co-inoculated with U. maydis, often lead to decreased disease severity caused by the pathogen. Here, we developed methods (liquid chromatography-mass spectrometry) to evaluate changes in relative concentration of metabolites produced during in vitro interactions between the endophyte and pathogen. Fungi were grown on two different media, in single and in confronted cultures. We used real-time PCR (qPCR) assays to measure relative changes in fungal biomass, that occurred in confronted cultures compared to single cultures. The results showed that most secondary metabolites are constitutively produced by each species. Metabolite profiles are complex for U. maydis (twenty chromatographic peaks detected) while relatively fewer compounds were detected for F. verticillioides (six chromatographic peaks). In confronted cultures, metabolite ratio (metabolite concentration/biomass) generally increases for U. maydis metabolites while no significant changes were observed for most F. verticillioides metabolites. The results show that F. verticillioides is a strong antagonist of U. maydis as its presence leads to large reductions in U. maydis biomass. We infer that few U. maydis metabolites likely serve antibiotic functions against F. verticillioides. The methods described here are sufficiently sensitive to detect small changes in biomass and metabolite concentration associated with differing genotypes of the interacting species.
本研究旨在确定内生尖孢镰刀菌（Sacc.）Nirenberg 菌株与病原菌玉米黑粉菌（DC）（Corda）之间相互作用的机制。内生真菌尖孢镰刀菌通常与玉米（Zea mays）相关联，当与玉米黑粉菌共同接种时，通常会导致病原菌引起的疾病严重程度降低。在这里，我们开发了方法（液相色谱-质谱法）来评估内生菌和病原菌之间体外相互作用过程中产生的代谢物相对浓度的变化。真菌在两种不同的培养基上生长，在单独和对峙培养中生长。我们使用实时 PCR（qPCR）测定来测量对峙培养中与单独培养相比真菌生物量的相对变化。结果表明，大多数次生代谢物是由每个物种组成型产生的。玉米黑粉菌的代谢物图谱复杂（检测到二十个色谱峰），而尖孢镰刀菌检测到的化合物相对较少（六个色谱峰）。在对峙培养中，玉米黑粉菌代谢物的代谢物比率（代谢物浓度/生物量）通常增加，而尖孢镰刀菌代谢物则没有观察到显著变化。结果表明，尖孢镰刀菌是玉米黑粉菌的强烈拮抗剂，因为其存在导致玉米黑粉菌生物量大量减少。我们推断，很少有玉米黑粉菌代谢物可能对尖孢镰刀菌具有抗生素功能。这里描述的方法足够灵敏，可以检测与相互作用物种不同基因型相关的生物量和代谢物浓度的微小变化。
