玉米萜类植保素代谢关键基因对小斑病侵染的防御响应分析

Gene Expression of Maize Terpenoid Phytoalexin Metabolism in Response to Southern Leaf Blight

该研究选用小斑病差异抗性的玉米自交系Mo17(较抗)、‘郑58’(中抗)和‘吉419’(感),分别于接种小斑病病原菌玉蜀黍平脐孺胞(Cochliobolus heterostrophus)0、6、12、24、36和48h时采集接种叶片为材料,采用半定量和实时荧光定量PCR技术,检测倍半萜植保素Zealexin生物合成关键基因(TPS6、TPS11)、二萜植保素Kauralexin代谢关键基因An2以及茉莉酸合成关键基因AOC的表达模式,为阐明不同抗性品种对玉米小斑病的差异防御机制提供理论依据。结果显示:接种小斑病病原菌后,抗病自交系Mo17中TPS6、TPS11基因表达诱导不显著,An2基因表达迅速增加,AOC基因于接种12h后表达明显上调。‘郑58’中TPS6、TPS11基因被快速诱导,在接种24h时表达量达到最大,An2基因表达逐渐增加但差异不显著,AOC基因表达量于接种6h后显著增加;感病自交系‘吉419’中TPS6、TPS11、An2基因在接种24h后才显著上调,明显比抗性自交系缓慢,AOC基因表达先呈现递减的趋势然后上升,在24h表达量最高并持续到48h。研究表明,两类植保素代谢在玉米小斑病防御中具有不同的时间应答模式,但都受到茉莉酸介导。感病自交系中植保素代谢防御响应较慢,而抗病自交系中响应较快,符合其抗性差异。

In this study,different disease-resistant inbred lines of maize,Mo17（high）,Zheng58（medium）,Ji419（low）,were inoculated with the pathogen spore of southern leaf blight,C.heterostrophus,for 0,6,12,24,36 and 48hours.Through semi-quantitative and real-time PCR technology,the expression patterns of some key genes were explored in response to pathogen infection,including TPS6 and TPS11for sesquiterpenoid phytoalexin Zealexin biosynthesis,An2 for diterpenoid phytoalexin Kauralexin biosynthesis,and AOC,the key gene of jasmonic acid（JA）metabolism.The results were followed：TPS6and TPS11 gene expression in Mo17 were not induced significantly while the gene accumulation of An2 increased rapidly after inoculation.In the mean time,AOCgene expression was significantly increased after inoculation for 12 h in Mo17.TPS6 and TPS11gene expression in Zheng58 increased rapidly,and reached the highest at 24 h.The An2 gene expression gradually increased,but the difference was not significant.The AOCgene expression increased significantly after inoculation for 6h.The TPS6,TPS11 and An2of Ji419 were upregulated in 24 h,slower than that in other two lines,and AOCgene expression showed a decreasing trend in the ear-ly phase and reached the highest levels at 24 hand 48h.These results indicated that two types of terpenoid phytoalexins exhibited different metabolic response temporally in response to C.heterostrophus inoculation,but both were mediated with JA signal.The defense response mediated by metabolism of terpenoid phytoalexin was faster in resistant inbred line than that in the susceptible one,which is consistent with their resistance difference.Investigation of the defense response for terpenes phytoalexin metabolic genes provided an important theoretical basis for clarifying the defense mechanisms of maize varieties with different resistance against southern leaf blight.