State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China.
Mol Plant Pathol. 2022 Jun;23(6):895-900. doi: 10.1111/mpp.13212. Epub 2022 Mar 24.
The soilborne ascomycete fungus Verticillium dahliae causes destructive vascular wilt disease in hundreds of dicotyledonous plant species. However, our understanding of the early invasion from the epidermis to the vasculature and the prompt proliferation and colonization in the xylem tissues remains poor. To elaborate the detailed infection strategy of V. dahliae in host plants, we traced the whole infection process of V. dahliae by live-cell imaging combined with high-resolution scanning electron microscopy. The 4D image series demonstrated that the apex of invading hyphae becomes tapered and directly invades the intercellular space of root epidermal cells at the initial infection. Following successful epidermal invasion, the invading hyphae extend in the intercellular space of the root cortex toward the vascular tissues. Importantly, the high-resolution microscopic and live-cell images demonstrated (a) that conidia are formed via budding at the apex of the hyphae in the xylem vessels to promote systemic propagation vertically, and (b) that the hyphae freely cross adjacent xylem vessels through the intertracheary pits to achieve horizontal colonization. Our findings provide a solid cellular basis for future studies on both intracellular invasion and vascular colonization/proliferation during V. dahliae infection and pathogenesis in host plants.
土壤丝孢真菌黄萎轮枝菌可引起数百种双子叶植物的破坏性维管束萎蔫病。然而，我们对其从表皮到维管束的早期入侵以及在木质部组织中的迅速增殖和定殖过程仍知之甚少。为了详细阐述黄萎轮枝菌在宿主植物中的感染策略，我们通过活细胞成像结合高分辨率扫描电子显微镜跟踪了黄萎轮枝菌的整个感染过程。4D 图像序列表明，侵染菌丝的顶端变细，并在初始侵染时直接侵入根表皮细胞的细胞间隙。成功的表皮侵染后，侵染菌丝在根皮层的细胞间隙中向维管束延伸。重要的是，高分辨率显微镜和活细胞图像显示：（a）在木质部导管中的菌丝顶端通过芽生形成分生孢子，以促进垂直的系统传播；（b）菌丝通过纹孔间自由穿过相邻的木质部导管，以实现水平定殖。我们的研究结果为进一步研究黄萎轮枝菌在宿主植物中的细胞内侵染以及维管束的侵染/增殖和发病机制提供了坚实的细胞学基础。
