Thiamine (Vitamin B_1) Plays a Critical Role on Sugar Utilization by the Phytopathogenic Fungus, Ustilago esculenta

摘要

Ustilago esculenta, inducing edible galls in its host Zizania latifolia, exhibits an obligate requirement for thiamine (vitamin B,) in axenic culture. The function of thiamine for growth in U. esculenta was investigated and compared with two closely related species, U. maydis (com smut) and U. scitaminea (sugarcane smut). Sucrose was readily broken into glucose and fructose, independent of thiamine, by all three fungal species tested. Growth of U. maydis and U. scitaminea was apparently not affected by thiamine when glucose or fructose was used as the sole carbon source. By contrast, U. esculenta was incapable of utilizing glucose and fructose in the absence of thiamine. Addition of thiamine into a synthetic medium drastically enhanced the growth of U. esculenta. In all cases, Ustilago species preferentially utilized glucose prior to fructose. Fmctose uptake in U. esculenta exhibited a saturated kinetic, indicative of carrier protein-mediated process. The uptake of fructose by U. esculenta was highly influenced by the amounts of glucose, and was likely via., a noncompetitive mode. Taken together, the results strongly indicate that thiamine plays a key role for glucose and fmctose metabolisms and energy production by U. esculenta.