Zhejiang Provincial Key Laboratory of Biometrology and Inspection & Quarantine, College of Life Sciences, China Jiliang University, Hangzhou, 310018, Zhejiang, China.
Jinhua Academy of Agricultural Sciences, Jinhua, Zhejiang, China.
BMC Microbiol. 2019 Sep 5;19(1):208. doi: 10.1186/s12866-019-1588-2.
Ustilago 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.
In 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.
Results 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.
稻黑粉菌是一种典型的二态真菌，可感染稻并诱导宿主茎部肿胀，形成在中国被称为茭白的可食用蔬菜。菌株分化，尤其是在交配能力和致病性方面，与田间形成的不同表型的茭白密切相关。二态转换是一种严格调控的过程，对于二态真菌的致病发育至关重要。在对外界环境线索的反应中，二态转换可以通过两条保守的细胞信号通路-PKA 和 MAPK 通路来激活。先前的研究表明，外源性精氨酸可以通过精氨酸酶水解在几种二态真菌中诱导菌丝形成，但抑制稻黑粉菌的二态转变。我们进行这项研究是为了揭示精氨酸对稻黑粉菌二态转变的功能。
在这项研究中，我们发现精氨酸而不是其代谢物可以按精氨酸浓度的比例减缓稻黑粉菌的二态转变。此外，预测编码稻黑粉菌中的精氨酸酶的 UeArginase 被克隆和表征。UeArginase 突变体实际上可以增加内源性精氨酸的含量，并在营养丰富或贫瘠的培养基上减缓二态转变。无论是添加外源性精氨酸还是 UeArginase 缺失，都会导致交配过程中 UePkaC、UePrf1、mfa1.2、mfa2.1、pra1 和 pra2 的表达下调，同时精氨酸含量增加。
这项研究的结果表明，精氨酸本身直接抑制稻黑粉菌的二态转变，而不依赖于其被 UeArginase 水解。
