Beseli Aydin, Goulart da Silva Marilia, Daub Margaret E
Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA.
Phytopathology Department; Federal University of Lavras, Lavras, MG, 37200-000, Brazil.
FEMS Microbiol Lett. 2015 Jan;362(2):1-7. doi: 10.1093/femsle/fnu036. Epub 2014 Dec 4.
The photosynthetic bacterium Rhodobacter sphaeroides and plant pathogenic fungus Cercospora nicotianae have been used as models for understanding resistance to singlet oxygen ((1)O(2)), a highly toxic reactive oxygen species. In Rhodobacter and Cercospora, (1)O(2) is derived, respectively, from photosynthesis and from the (1)O(2)-generating toxin cercosporin which the fungus produces to parasitize plants. We identified common genes recovered in transcriptome studies of putative (1)O(2)-resistance genes in these two systems, suggesting common (1)O(2)-resistance mechanisms. To determine if the Cercospora homologs of R. sphaeroides (1)O(2)-resistance genes are involved in resistance to cercosporin, we expressed the genes in the cercosporin-sensitive fungus Neurospora crassa and assayed for increases in cercosporin resistance. Neurospora crassa transformants expressing genes encoding aldo/keto reductase, succinyl-CoA ligase, O-acetylhomoserine (thiol) lyase, peptide methionine sulphoxide reductase and glutathione S-transferase did not have elevated levels of cercosporin resistance. Several transformants expressing aldehyde dehydrogenase were significantly more resistant to cercosporin. Expression of the transgene and enzyme activity did not correlate with resistance, however. We conclude that although the genes tested in this study are important in (1)O(2) resistance in R. sphaeroides, their Cercospora homologs are not involved in resistance to (1)O(2) generated from cercosporin.
光合细菌球形红杆菌和植物致病真菌烟草尾孢菌已被用作理解对单线态氧（¹O₂）抗性的模型，单线态氧是一种剧毒的活性氧物质。在红杆菌和尾孢菌中，¹O₂分别来源于光合作用和真菌产生的用于寄生植物的产¹O₂毒素尾孢菌素。我们在这两个系统中推定的¹O₂抗性基因转录组研究中鉴定出了共同的基因，这表明存在共同的¹O₂抗性机制。为了确定球形红杆菌¹O₂抗性基因在尾孢菌中的同源物是否参与对尾孢菌素的抗性，我们在对尾孢菌素敏感的真菌粗糙脉孢菌中表达了这些基因，并检测尾孢菌素抗性是否增加。表达编码醛醇/酮还原酶、琥珀酰辅酶A连接酶、O-乙酰高丝氨酸（硫醇）裂解酶、肽甲硫氨酸亚砜还原酶和谷胱甘肽S-转移酶基因的粗糙脉孢菌转化体对尾孢菌素的抗性水平并未提高。几个表达醛脱氢酶的转化体对尾孢菌素的抗性显著增强。然而，转基因表达和酶活性与抗性并不相关。我们得出结论，尽管本研究中测试的基因在球形红杆菌对¹O₂的抗性中很重要，但其在尾孢菌中的同源物并不参与对尾孢菌素产生的¹O₂的抗性。
