Schlemmer Timo, Lischka Richard, Wegner Linus, Ehlers Katrin, Biedenkopf Dagmar, Koch Aline
Centre for BioSystems, Land Use and Nutrition, Institute of Phytopathology, Justus Liebig University, Heinrich-Buff-Ring 26, 35392, Giessen, Germany.
Institute of Phytomedicine, University of Hohenheim, Otto-Sander-Strasse 5, 70599, Stuttgart, Germany.
Fungal Biol Biotechnol. 2022 Jul 14;9(1):14. doi: 10.1186/s40694-022-00143-w.
Numerous reports have shown that incorporating a double-stranded RNA (dsRNA)-expressing transgene into plants or applying dsRNA by spraying it onto their leaves successfully protects them against invading pathogens exploiting the mechanism of RNA interference (RNAi). How dsRNAs or siRNAs are transferred between donor host cells and recipient fungal cells is largely unknown. It is speculated that plant extracellular vesicles (EVs) function as RNA shuttles between plants and their pathogens. Recently, we found that EVs isolated from host-induced gene silencing (HIGS) or spray-induced gene silencing (SIGS) plants contained dsRNA-derived siRNAs. In this study, we evaluated whether isolated EVs from dsRNA-sprayed barley (Hordeum vulgare) plants affected the growth of the phytopathogenic ascomycete Fusarium graminearum. Encouraged by our previous finding that dropping barley-derived EVs on F. graminearum cultures caused fungal stress phenotypes, we conducted an in vitro growth experiment in microtiter plates where we co-cultivated F. graminearum with plant EVs isolated from dsRNA-sprayed barley leaves. We observed that co-cultivation of F. graminearum macroconidia with barley EVs did not affect fungal growth. Furthermore, plant EVs containing SIGS-derived siRNA appeared not to affect F. graminearum growth and showed no gene silencing activity on F. graminearum CYP51 genes. Based on our findings, we concluded that either the amount of SIGS-derived siRNA was insufficient to induce target gene silencing in F. graminearum, indicating that the role of EVs in SIGS is minor, or that F. graminearum uptake of plant EVs from liquid cultures was inefficient or impossible.
众多报告表明，将表达双链RNA（dsRNA）的转基因导入植物，或通过将dsRNA喷洒在植物叶片上，利用RNA干扰（RNAi）机制可成功保护植物抵御入侵病原体。dsRNA或小干扰RNA（siRNA）如何在供体宿主细胞和受体真菌细胞之间转移，目前尚不清楚。据推测，植物细胞外囊泡（EVs）在植物与其病原体之间充当RNA穿梭载体。最近，我们发现从宿主诱导基因沉默（HIGS）或喷雾诱导基因沉默（SIGS）植物中分离出的EVs含有源自dsRNA的siRNA。在本研究中，我们评估了从喷洒dsRNA的大麦（Hordeum vulgare）植株中分离出的EVs是否会影响植物病原性子囊菌禾谷镰刀菌（Fusarium graminearum）的生长。鉴于我们之前发现将大麦来源的EVs滴加到禾谷镰刀菌培养物上会导致真菌应激表型，我们在微量滴定板中进行了体外生长实验，将禾谷镰刀菌与从喷洒dsRNA的大麦叶片中分离出的植物EVs共同培养。我们观察到，禾谷镰刀菌大分生孢子与大麦EVs共同培养并不影响真菌生长。此外，含有SIGS来源siRNA的植物EVs似乎不影响禾谷镰刀菌的生长，并且对禾谷镰刀菌CYP51基因没有基因沉默活性。基于我们的研究结果，我们得出结论，要么是SIGS来源的siRNA量不足以诱导禾谷镰刀菌中的靶基因沉默，这表明EVs在SIGS中的作用较小，要么是禾谷镰刀菌从液体培养物中摄取植物EVs的效率低下或无法摄取。
