Fusarium graminearum produces trichothecene mycotoxins in infected grains and axenic liquid culture. A proposed regulatory model of trichothecene biosynthesis was examined in relation to nitrogen utilization. First, we showed that an important factor for the stimulation of trichothecene biosynthesis was not the occurrence of agmatine as a specific inducer molecule, but rather continuous acidification of the liquid culture medium arising from agmatine catabolism. When the pH of the l-Gln synthetic medium was frequently adjusted to the pH of the agmatine culture, trichothecene productivity of the l-Gln culture was equal to that of the agmatine culture. For efficient trichothecene biosynthesis, the culture pH should be lowered at an appropriate time point during the early growth stage. Second, we re-evaluated the role of the nitrogen regulatory GATA transcription factor AreA in trichothecene biosynthesis. Since Tri6 encodes a transcription factor indispensable for trichothecene biosynthesis, all fifteen AreA-binding consensus sequences in the Tri6 promoter were mutated. The mutant could catabolize l-Phe as the sole nitrogen source; furthermore, the pH profile of the synthetic l-Phe medium (initial pH 4.2) was the same as that of the wild-type (WT) strain. Under such conditions, the promoter mutant exhibited approximately 72% of the trichothecene productivity compared to the WT strain. Thus, F. graminearum AreA (FgAreAp) is dispensable for the functioning of the Tri6 promoter, but it contributes to the increased production of mycotoxin under mildly acidic conditions to some extent. Further investigations on the culture pH revealed that extremely low pH bypasses the function of FgAreAp.

禾谷镰刀菌（Fusarium graminearum）在受感染的谷物和未成熟的液体培养物中产生天花粉真菌毒素。拟议的天花粉生物合成的监管模型进行了审查与氮利用。首先，我们表明，刺激天花粉生物合成的重要因素不是胍丁胺作为特定诱导剂分子的出现，而是由于胍丁胺分解代谢引起的液体培养基的连续酸化。当的pH升-Gln合成培养基经常被调节至pH值的胍丁胺的文化，所述的单端孢生产率升-Gln培养与胍丁胺培养相等。为了有效地进行单端孢菌素生物合成，应在生长早期的适当时间点降低培养液的pH值。其次，我们重新评估了氮调节性GATA转录因子AreA在单端孢菌素生物合成中的作用。由于Tri6编码了单端孢菌素生物合成必不可少的转录因子，因此Tri6启动子中的所有十五个AreA结合共有序列都发生了突变。该突变体可以分解代谢1-苯丙氨酸作为唯一的氮源。此外，合成的pH分布升-Phe培养基（初始pH 4.2）与野生型（WT）菌株相同。在这种条件下，与WT菌株相比，启动子突变体表现出约72％的单端孢菌素产率。因此，禾谷镰刀菌AreA（FgAreAp）对于Tri6启动子的功能是必不可少的，但在中等酸性条件下，它有助于霉菌毒素的产生增加。对培养液pH值的进一步研究表明，极低的pH值会绕过FgAreAp的功能。