Kohut Gábor, Adám Attila L, Fazekas Béla, Hornok László
Agricultural Biotechnology Center, Mycology Group of the Hungarian Academy of Sciences, Institute of Plant Protection, Szent István University, H-2100 Gödöllo, Páter K. u.1., Hungary.
Int J Food Microbiol. 2009 Mar 15;130(1):65-9. doi: 10.1016/j.ijfoodmicro.2009.01.002. Epub 2009 Jan 9.
During cultivation of a wild type strain of Fusarium proliferatum on ammonium dihydrogen phosphate containing defined medium, expression levels of FUM1 and FUM8, members of the fumonisin biosynthesis gene cluster significantly increased when ammonium ion concentration of the culture medium decreased below 10 mM, indicating that N-depletion triggers the fumonisin biosynthesis genes. Deletion of Fphog1, a HOG-type MAP kinase gene resulted in further increases in FUM1 and FUM8 expression under nitrogen starvation (absence of any N-source) conditions. Fumonisin B1 (FB1) production paralleled with increased FUM gene expression: significant amounts of FB1 were measured in culture filtrates of the DeltaFphog1 deleted mutant after five days culturing, whereas only traces of FB1 could be detected in filtrates of the wild type and the restored strain (R1) complemented with the wild-type Fphog1-24 gene. N-starvation strongly retarded the growth of the DeltaFphog1 mutant in comparison to wild type. The up-regulation of fumonisin biosynthesis genes in the DeltaFphog1 mutant could be explained by the increased sensitivity of these strains to N-starvation stress that appears in the absence of an intact HOG-type MAPK pathway.
在用含磷酸二氢铵的限定培养基培养野生型层出镰刀菌菌株的过程中,当培养基中铵离子浓度降至10 mM以下时,伏马毒素生物合成基因簇成员FUM1和FUM8的表达水平显著增加,这表明氮耗竭会触发伏马毒素生物合成基因。缺失HOG型丝裂原活化蛋白激酶基因Fphog1会导致在氮饥饿(无任何氮源)条件下FUM1和FUM8的表达进一步增加。伏马毒素B1(FB1)的产生与FUM基因表达的增加平行:在缺失DeltaFphog1的突变体培养五天后的培养滤液中检测到大量的FB1,而在野生型和用野生型Fphog1 - 24基因互补的回复菌株(R1)的滤液中仅检测到痕量的FB1。与野生型相比,氮饥饿强烈抑制了DeltaFphog1突变体的生长。DeltaFphog1突变体中伏马毒素生物合成基因的上调可以通过这些菌株对氮饥饿胁迫的敏感性增加来解释,这种敏感性在缺乏完整的HOG型丝裂原活化蛋白激酶途径时出现。