Previously, we have demonstrated that transgenic Arabidopsis and barley plants, expressing a 791 nucleotide (nt) dsRNA (CYP3RNA) that targets all three CYP51 genes (FgCYP51A, FgCYP51B, FgCYP51C) in Fusarium graminearum (Fg), inhibited fungal infection via a process designated as host-induced gene silencing (HIGS). More recently, we have shown that spray applications of CYP3RNA also protect barley from fungal infection via a process termed spray-induced gene silencing (SIGS). Thus, RNAi technology may have the potential to revolutionize plant protection in agriculture. Therefore, successful field application will require optimization of RNAi design necessary to maximize the efficacy of the RNA silencing construct for making RNAi-based strategies a realistic and sustainable approach in agriculture. Previous studies indicate that silencing is correlated with the number of siRNAs generated from a dsRNA precursor. To prove the hypothesis that silencing efficiency is correlated with the number of siRNAs processed out of the dsRNA precursor, we tested in a HIGS and SIGS approach dsRNA precursors of increasing length ranging from 400 nt to 1500 nt to assess gene silencing efficiency of individual FgCYP51 genes. Concerning HIGS-mediated disease control, we found that there is no significant correlation between the length of the dsRNA precursor and the reduction of Fg infection on CYP51-dsRNA-expressing Arabidopsis plants. Importantly and in clear contrast to HIGS, we measured a decrease in SIGS-mediated Fg disease resistance that significantly correlates with the length of the dsRNA construct that was sprayed, indicating that the size of the dsRNA interferes with a sufficient uptake of dsRNAs by the fungus.

此前，我们已经证明，转基因拟南芥和大麦植株表达791个核苷酸（nt）双链RNA（CYP3RNA），其目标全部三个CYP51基因（FgCYP51A，FgCYP51B，FgCYP51C）在禾谷镰刀菌（蛋白原），通过称为宿主诱导的基因沉默（HIGS）的过程抑制了真菌感染。最近，我们发现CYP3RNA的喷雾施用还通过称为喷雾诱导的基因沉默（SIGS）的过程保护大麦免受真菌感染。因此，RNAi技术可能具有革新农业中植物保护的潜力。因此，成功的现场应用将需要优化RNAi设计，以使RNA沉默构建体的功效最大化，从而使基于RNAi的策略成为农业上现实可行的可持续方法。先前的研究表明沉默与从dsRNA前体产生的siRNA的数量有关。为了证明以下假设：沉默效率与从dsRNA前体中加工出的siRNA的数量有关，FgCYP51基因。关于HIGS介导的疾病控制，我们发现dsRNA前体的长度与表达CYP51-dsRNA的拟南芥植物上Fg感染的减少之间没有显着相关性。重要的是，与HIG​​S形成鲜明对比的是，我们测量到SIGS介导的Fg病抗性降低与喷洒的dsRNA构建体的长度显着相关，这表明dsRNA的大小干扰了真菌对dsRNA的充分吸收。