Ridenour John B, Smith Jonathon E, Bluhm Burton H
Department of Plant Pathology, Division of Agriculture, University of Arkansas, Fayetteville, Arkansas 72701, USA.
J Food Prot. 2016 Sep;79(9):1498-1507. doi: 10.4315/0362-028X.JFP-15-596.
Contamination of maize ( Zea mays ) with fumonisins produced by the fungus Fusarium verticillioides is a global concern for food safety. Fumonisins are a group of polyketide-derived secondary metabolites linked to esophageal cancer and neural tube birth defects in humans and numerous toxicoses in livestock. Despite the importance of fumonisins in global maize production, the regulation of fumonisin biosynthesis during kernel pathogenesis is poorly understood. The HAP complex is a conserved, heterotrimeric transcriptional regulator that binds the consensus sequence CCAAT to modulate gene expression. Recently, functional characterization of the Hap3 subunit linked the HAP complex to the regulation of secondary metabolism and stalk rot pathogenesis in F. verticillioides . Here, we determine the involvement of HAP3 in fumonisin biosynthesis and kernel pathogenesis. Deletion of HAP3 suppressed fumonisin biosynthesis on both nonviable and live maize kernels and impaired pathogenesis in living kernels. Transcriptional profiling via RNA sequencing indicated that the HAP complex regulates at least 1,223 genes in F. verticillioides , representing nearly 10% of all predicted genes. Disruption of the HAP complex caused the misregulation of biosynthetic gene clusters underlying the production of secondary metabolites, including fusarins. Taken together, these results reveal that the HAP complex is a central regulator of fumonisin biosynthesis and kernel pathogenesis and works as both a positive and negative regulator of secondary metabolism in F. verticillioides .
玉米（Zea mays）被轮枝镰孢菌（Fusarium verticillioides）产生的伏马毒素污染是全球食品安全关注的问题。伏马毒素是一类由聚酮衍生的次生代谢产物，与人类食管癌和神经管出生缺陷以及家畜的多种中毒有关。尽管伏马毒素在全球玉米生产中很重要，但在玉米粒发病过程中伏马毒素生物合成的调控却知之甚少。HAP复合物是一种保守的异源三聚体转录调节因子，它结合共有序列CCAAT来调节基因表达。最近，Hap3亚基的功能表征将HAP复合物与轮枝镰孢菌的次生代谢调控和茎腐病发病机制联系起来。在这里，我们确定了HAP3在伏马毒素生物合成和玉米粒发病机制中的作用。HAP3的缺失抑制了非活玉米粒和活玉米粒上伏马毒素的生物合成，并损害了活玉米粒的发病机制。通过RNA测序进行的转录谱分析表明，HAP复合物在轮枝镰孢菌中调节至少1223个基因，占所有预测基因的近10%。HAP复合物的破坏导致次生代谢产物（包括镰刀菌素）生物合成基因簇的调控失调。综上所述，这些结果表明，HAP复合物是伏马毒素生物合成和玉米粒发病机制的核心调节因子，并且在轮枝镰孢菌中作为次生代谢的正调节因子和负调节因子发挥作用。
