Teichert Sabine, Wottawa Marieke, Schönig Birgit, Tudzynski Bettina
Westfälische Wilhelms-Universität Münster, Institut für Botanik, Schlossgarten 3, D-48149 Münster, Germany.
Eukaryot Cell. 2006 Oct;5(10):1807-19. doi: 10.1128/EC.00039-06.
In Fusarium fujikuroi, the biosynthesis of gibberellins (GAs) and bikaverin is under control of AreA-mediated nitrogen metabolite repression. Thus far, the signaling components acting upstream of AreA and regulating its nuclear translocation are unknown. In Saccharomyces cerevisiae, the target of rapamycin (TOR) proteins, Tor1p and Tor2p, are key players of nutrient-mediated signal transduction to control cell growth. In filamentous fungi, probably only one TOR kinase-encoding gene exists. However, nothing is known about its function. Therefore, we investigated the role of TOR in the GA-producing fungus F. fujikuroi in order to determine whether TOR plays a role in nitrogen regulation, especially in the regulation of GA and bikaverin biosynthesis. We cloned and characterized the F. fujikuroi tor gene. However, we were not able to create knockout mutants, suggesting that TOR is essential for viability. Inhibition of TOR by rapamycin affected the expression of AreA-controlled secondary metabolite genes for GA and bikaverin biosynthesis, as well as genes involved in transcriptional and translational regulation, ribosome biogenesis, and autophagy. Deletion of fpr1 encoding the FKBP12-homologue confirmed that the effects of rapamycin are due to the specific inhibition of TOR. Interestingly, the expression of most of the TOR target genes has been previously shown to be also affected in the glutamine synthetase mutant, although in the opposite way. We demonstrate here for the first time in a filamentous fungus that the TOR kinase is involved in nitrogen regulation of secondary metabolism and that rapamycin affects also the expression of genes involved in translation control, ribosome biogenesis, carbon metabolism, and autophagy.
在藤仓镰孢菌中,赤霉素(GAs)和比卡维林的生物合成受AreA介导的氮代谢物阻遏调控。迄今为止,作用于AreA上游并调节其核转位的信号成分尚不清楚。在酿酒酵母中,雷帕霉素靶蛋白(TOR)Tor1p和Tor2p是营养介导的信号转导控制细胞生长的关键因子。在丝状真菌中,可能仅存在一个编码TOR激酶的基因。然而,其功能尚无定论。因此,我们研究了TOR在产GA的藤仓镰孢菌中的作用,以确定TOR是否在氮调节中发挥作用,特别是在GA和比卡维林生物合成的调节中。我们克隆并鉴定了藤仓镰孢菌的tor基因。然而,我们无法创建基因敲除突变体,这表明TOR对细胞活力至关重要。雷帕霉素抑制TOR会影响AreA控制的GA和比卡维林生物合成的次生代谢物基因的表达,以及参与转录和翻译调控、核糖体生物合成和自噬的基因的表达。缺失编码FKBP12同源物的fpr1证实了雷帕霉素的作用是由于对TOR的特异性抑制。有趣的是,大多数TOR靶基因的表达先前已被证明在谷氨酰胺合成酶突变体中也受到影响,尽管方式相反。我们首次在丝状真菌中证明,TOR激酶参与次生代谢的氮调节,并且雷帕霉素还影响参与翻译控制、核糖体生物合成、碳代谢和自噬的基因的表达。