Fusarium graminearum, the main pathogenic fungus causing Fusarium head blight (FHB), produces deoxynivalenol (DON), a key virulence factor, which is synthesized in the endoplasmic reticulum (ER). Sey1/atlastin, a dynamin-like GTPase protein, is known to be required for homotypic fusion of ER membranes, but the functions of this protein are unknown in pathogenic fungi. Here, we characterized a Sey1/atlastin homologue FgSey1 in F. graminearum. Like Sey1/atlastin, FgSey1 is located in the ER. The FgSEY1 deletion mutant exhibited significantly reduced vegetative growth, asexual development, DON biosynthesis and virulence. Moreover, the Fgsey1 mutant was impaired in the formation of normal lipid droplets (LDs) and toxisomes, both of which participate in DON biosynthesis. The GTPase, helix bundles (HBs), transmembrane segments (TMs) and cytosolic tail (CT) domains of FgSey1 are essential for its function, but only the TMs domain is responsible for its localization. Furthermore, the mutants FgSey1^K63A and FgSey1^T87A lacked GTPase activity and failed to rescue the defects of the Fgsey1 mutant. Collectively, our data suggest that the dynamin-like GTPase protein FgSey1 affects the generation of LDs and toxisomes and is required for DON biosynthesis and pathogenesis in F. graminearum.

IMPORTANCE Fusarium graminearum is a major plant pathogen that causes Fusarium head blight (FHB) of wheats worldwide. In addition to reduce the plant yield, F. graminearum infection of wheats also produce deoxynivalenol (DON) mycotoxins, which are harmful to humans and animals, and therefore cause great economic losses through polluting food products and animal feed. At present, effective strategies for controlling FHB are not available. Therefore, understanding of the regulation mechanisms of fungal development, pathogenesis and DON biosynthesis is important for the development effective control strategies of this disease. In this study, we demonstrated that a dynamin-like GTPase protein Sey1/atlastin homologue FgSey1, is required for vegetative growth, DON production and pathogenicity in F. graminearum. Our results provide the novel information on FgSey1 critical roles in fungal pathogenicity, and therefore FgSey1 could be a potential target for effective control measure of the disease caused by F. graminearum.

禾谷镰刀菌（Fusarium graminearum）是引起镰刀菌枯萎病（FHB）的主要致病真菌，可产生脱氧雪腐烯醇（DON），这是一种重要的毒力因子，在内质网（ER）中合成。Sey1 / atlastin是一种类似动力蛋白的GTPase蛋白，已知是ER膜同型融合所必需的，但该蛋白的功能在致病性真菌中尚不清楚。在这里，我们的特点在Sey1 / atlastin同源FgSey1禾谷镰刀菌。与Sey1 / atlastin一样，FgSey1也位于ER中。所述FgSEY1缺失突变体显示出降低显著营养生长，无性发展，DON生物合成和毒力。此外，Fgsey1突变体在正常脂质滴（LDs）和毒素体的形成中受损，它们都参与DON的生物合成。FgSey1的GTPase，螺旋束（HBs），跨膜片段（TMs）和胞质尾部（CT）域对其功能至关重要，但只有TMs域负责其定位。此外，突变体FgSey1 ^K63A和FgSey1 ^T87A缺乏GTPase活性，未能挽救Fgsey1突变体的缺陷。总体而言，我们的数据表明，类似动力蛋白的GTPase蛋白FgSey1影响LD和毒素的生成，是DON生物合成和禾谷镰刀菌发病的必需条件。

重要信息 禾谷镰孢（Fusarium graminearum）是一种主要的植物病原体，可导致全球小麦的枯萎病。除降低植物产量外，禾谷镰刀菌小麦的感染还会产生脱氧雪腐酚（DON）霉菌毒素，对人体和动物有害，因此通过污染食品和动物饲料而造成巨大的经济损失。目前，尚无控制FHB的有效策略。因此，了解真菌发育，发病机制和DON生物合成的调控机制对于发展该病的有效控制策略具有重要意义。在这项研究中，我们证明了生长激素样的GTPase蛋白Sey1 / atlastin同源FgSey1，是禾本科植物营养生长，DON产生和致病性所必需的。。我们的结果提供了有关FgSey1在真菌致病性中的关键作用的新信息，因此FgSey1可能成为有效控制禾谷镰刀菌所致疾病的潜在靶标。