Department of Genetics, Faculty of Biology, University of Seville, Seville, Spain.
Appl Environ Microbiol. 2012 Oct;78(20):7258-66. doi: 10.1128/AEM.01552-12. Epub 2012 Aug 3.
Fusarins are a class of mycotoxins of the polyketide family produced by different Fusarium species, including the gibberellin-producing fungus Fusarium fujikuroi. Based on sequence comparisons between polyketide synthase (PKS) enzymes for fusarin production in other Fusarium strains, we have identified the F. fujikuroi orthologue, called fusA. The participation of fusA in fusarin biosynthesis was demonstrated by targeted mutagenesis. Fusarin production is transiently stimulated by nitrogen availability in this fungus, a regulation paralleled by the fusA mRNA levels in the cell. Illumination of the cultures results in a reduction of the fusarin content, an effect partially explained by a high sensitivity of these compounds to light. Mutants of the fusA gene exhibit no external phenotypic alterations, including morphology and conidiation, except for a lack of the characteristic yellow and/or orange pigmentation of fusarins. Moreover, the fusA mutants are less efficient than the wild type at degrading cellophane on agar cultures, a trait associated with pathogenesis functions in Fusarium oxysporum. The fusA mutants, however, are not affected in their capacities to grow on plant tissues.
镰刀菌素是多酮家族的一类真菌毒素，由不同的镰刀菌属产生，包括产生赤霉素的镰刀菌属真菌 Fusarium fujikuroi。基于其他 Fusarium 菌株中用于镰刀菌素生产的聚酮合酶（PKS）酶之间的序列比较，我们已经鉴定出 F. fujikuroi 的同源物，称为 fusA。通过靶向诱变证明了 fusA 参与了镰刀菌素的生物合成。在这种真菌中，氮的可用性会短暂地刺激镰刀菌素的产生，这种调节与细胞中 fusA mRNA 水平平行。培养物的光照会导致镰刀菌素含量降低，这种效应部分可以解释为这些化合物对光的高度敏感。fusA 基因突变体除了缺乏镰刀菌素的特征性黄色和/或橙色色素沉着外，没有表现出任何外部表型改变，包括形态和分生孢子形成。此外，fusA 突变体在琼脂培养物上降解纤维素的效率低于野生型，这一特性与 Fusarium oxysporum 的致病功能有关。然而，fusA 突变体在其在植物组织上生长的能力方面不受影响。
