Abstract
BackgroundUstilago esculenta, a typical dimorphic fungus could infect Zizania latifolia and induce host stem swollen to form an edible vegetable called Jiaobai in China. The strains differentiation especially in the mating ability and pathogenicity is closely related to different phenotypes of Jiaobai formed in the fields. Dimorphic switching, a tightly regulated processes, is essential for the pathogenetic development of dimorphic fungi. In responses to environment cues, dimorphic switching can be activated through two conserved cell signaling pathways-PKA and MAPK pathways. Previous study indicated that exogenous arginine could induce hyphal formation in several dimorphic fungi through hydrolysis by arginase, but inhibit the dimorphic transition of U. esculenta. We conducted this study to reveal the function of arginine on dimorphic transition of U. esculenta.ResultsIn this study, we found that arginine, but not its anabolites, could slow down the dimorphic transition of U. esculenta proportionally to the concentration of arginine. Besides, UeArginase, predicated coding arginase in U. esculenta was cloned and characterized. UeArginase mutants could actually increase the content of endogenous arginine, and slow down the dimorphic transition on either nutritious rich or poor medium. Either adding exogenous arginine or UeArginase deletion lead to down regulated expressions of UePkaC, UePrf1, mfa1.2, mfa2.1, pra1 and pra2, along with an increased content of arginine during mating process.ConclusionResults of this study indicated a direct role of arginine itself on the inhibition of dimorphic transition of U. esculenta, independent of its hydrolysis by UeArginase.
Highlights
Ustilago esculenta, a typical dimorphic fungus could infect Zizania latifolia and induce host stem swollen to form an edible vegetable called Jiaobai in China
We examined the dimorphic transition process after 10 mM arginine added under both nutrient-rich condition (YEPS medium) and nutrient-poor condition (BM medium)
After 10 mM arginine added, a small amount of conjugation tubes formed at 24 h under nutrient-rich condition or at 36 h under nutrient-poor condition (Table 1), indicating a ~ 12 h delay in dimorphic switching caused by 10 mM exogenous arginine
Summary
A typical dimorphic fungus could infect Zizania latifolia and induce host stem swollen to form an edible vegetable called Jiaobai in China. A tightly regulated processes, is essential for the pathogenetic development of dimorphic fungi. Known as a tightly regulated processes that switching between hyphal growth and yeastlike state, is essential for the pathogenesis of both animal and plant pathogenic dimorphic fungi [1]. In the typical smut fungus U. maydis, dimorphism is a particular irreversible growth form that switching from a haploid, unicellular phase to a dikaryotic filamentous stage [1]. It implies a critical role of mating (including cell fusion and hyphal growth in the life cycle) in pathogenetic development [10]. There is no report of arginine involved in dimorphism of U. maydis and other smut fungi
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