Crop varieties exhibited phenotype variations during domestication and breeding. Such phenotype variations include secondary metabolism differentiation; however, the underlying mechanisms remain to be clarified. Here, two elite maize inbred lines Mo17 and HZ4 were analyzed to determine constitutive phytoalexin accumulation including zealexins and kauralexins. Both inbred lines produced phytoalexins in above- and belowground tissues in sterile culture. HZ4 accumulated much more kauralexin A3 than Mo17, which was consistent with higher gene expression of kauralexin biosynthesis in HZ4. Promoter cloning and sequence analysis disclosed a number of sequence variations including fragment insertion/deletion and nucleotide substitution in promoter regions of both inbred lines. Further analysis showed that one key biosynthetic gene ( KSL5 ) of maize phytoalexins exhibited higher promoter activity in HZ4 than in Mo17. The underlying mechanism was explored and promoter mutation in both inbred lines accounted for such promoter activity difference. Specifically, one W-box element with a positive effect in KSL5 promoter from HZ4 was identified; meanwhile, a 413-bp fragment in KSL5 promoter from Mo17 played a negative role in gene expression. Both inbred lines accumulated these sequence mutations in promoters during breeding, which resulted in different gene expression and phytoalexin production, potentially contributing to basic resistance.

中文翻译：

---

两个玉米自交系植物抗毒素差异积累的启动子变异结果

作物品种在驯化和育种过程中表现出表型变异。这种表型变异包括次级代谢分化；然而，潜在的机制仍有待澄清。在这里，对两个优良玉米自交系 Mo17 和 HZ4 进行了分析，以确定组成型植物抗毒素积累，包括玉米抗毒素和 Kauralexins。两个近交系在无菌培养的地上和地下组织中产生植物抗毒素。HZ4 比 Mo17 积累了更多的 Kauralexin A3，这与 HZ4 中 Kauralexin 生物合成的更高基因表达一致。启动子克隆和序列分析揭示了许多序列变异，包括两个自交系的启动子区域中的片段插入/缺失和核苷酸替换。进一步分析表明，玉米植物抗毒素的一个关键生物合成基因（KSL5）在 HZ4 中比在 Mo17 中表现出更高的启动子活性。探索了潜在机制，两个自交系中的启动子突变解释了这种启动子活性差异。具体而言，鉴定了一种对来自 HZ4 的 KSL5 启动子具有积极作用的 W-box 元件；同时，来自 Mo17 的 KSL5 启动子中的 413 bp 片段在基因表达中起负面作用。两个近交系在育种期间在启动子中积累了这些序列突变，导致不同的基因表达和植物抗毒素产生，可能有助于基本抗性。探索了潜在机制，两个自交系中的启动子突变解释了这种启动子活性差异。具体而言，鉴定了一种对来自 HZ4 的 KSL5 启动子具有积极作用的 W-box 元件；同时，来自 Mo17 的 KSL5 启动子中的 413 bp 片段在基因表达中起负面作用。两个近交系在育种期间在启动子中积累了这些序列突变，导致不同的基因表达和植物抗毒素产生，可能有助于基本抗性。探索了潜在机制，两个自交系中的启动子突变解释了这种启动子活性差异。具体而言，鉴定了一种对来自 HZ4 的 KSL5 启动子具有积极作用的 W-box 元件；同时，来自 Mo17 的 KSL5 启动子中的 413 bp 片段在基因表达中起负面作用。两个近交系在育种期间在启动子中积累了这些序列突变，导致不同的基因表达和植物抗毒素产生，可能有助于基本抗性。