State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
University of Chinese Academy of Sciences, Beijing, China.
PLoS One. 2021 Jul 30;16(7):e0250064. doi: 10.1371/journal.pone.0250064. eCollection 2021.
The ascomycete fungus Fusarium oxysporum f.sp. cucumerinum causes vascular wilt diseases in cucumber. However, few genes related to morphogenesis and pathogenicity of this fungal pathogen have been functionally characterized. BLASTp searches of the Aspergillus fumigatus UgmA and galatofuranosyltransferases (Galf-transferases) sequences in the F. oxysporum genome identified two genes encoding putative UDP-galactopyranose mutase (UGM), ugmA and ugmB, and six genes encoding putative Galf-transferase homologs. In this study, the single and double mutants of the ugmA, ugmB and gfsB were obtained. The roles of UGMs and GfsB were investigated by analyzing the phenotypes of the mutants. Our results showed that deletion of the ugmA gene led to a reduced production of galactofuranose-containing sugar chains, reduced growth and impaired conidiation of F. oxysporum f.sp. cucumerinum. Most importantly, the ugmA deletion mutant lost the pathogenicity in cucumber plantlets. Although deletion of the ugmB gene did not cause any visible phenotype, deletion of both ugmA and ugmB genes caused more severe phenotypes as compared with the ΔugmA, suggesting that UgmA and UgmB are redundant and they can both contribute to synthesis of UDP-Galf. Furthermore, the ΔgfsB exhibited an attenuated virulence although no other phenotype was observed. Our results demonstrate that the galactofuranose (Galf) synthesis contributes to the cell wall integrity, germination, hyphal growth, conidiation and virulence in Fusarium oxysporum f.sp. cucumerinum and an ideal target for the development of new anti-Fusarium agents.
尖孢镰刀菌古巴专化型引起黄瓜的维管束萎蔫病。然而，这种真菌病原体的形态发生和致病性相关的基因很少被功能表征。在尖孢镰刀菌基因组中对构巢曲霉 UgmA 和半乳糖呋喃糖基转移酶（Galf-转移酶）序列进行 BLASTp 搜索，鉴定出两个编码假定的 UDP-半乳糖吡喃糖变位酶（UGM），ugmA 和 ugmB，和六个编码假定的 Galf-转移酶同源物的基因。在这项研究中，获得了 ugmA、ugmB 和 gfsB 的单突变体和双突变体。通过分析突变体的表型研究了 UGMs 和 GfsB 的作用。我们的结果表明，ugmA 基因的缺失导致半乳糖呋喃糖含量糖链的产生减少，尖孢镰刀菌古巴专化型的生长和分生孢子形成受损。最重要的是，ugmA 缺失突变体丧失了对黄瓜幼苗的致病性。虽然 ugmB 基因的缺失没有引起任何可见的表型，但与 ΔugmA 相比，缺失 ugmA 和 ugmB 基因引起的表型更为严重，表明 UgmA 和 UgmB 是冗余的，它们都可以有助于 UDP-Galf 的合成。此外，尽管没有观察到其他表型，但 ΔgfsB 表现出较弱的毒力。我们的结果表明，半乳糖呋喃糖（Galf）的合成有助于尖孢镰刀菌古巴专化型细胞壁的完整性、萌发、菌丝生长、分生孢子形成和毒力，是开发新型抗镰刀菌剂的理想靶点。
