Phytopathology. 1999 Sep;89(9):737-47. doi: 10.1094/PHYTO.1999.89.9.737.
ABSTRACT We have investigated the histology of infection of maize seedlings by Fusarium moniliforme in association with a biochemical host defense response, the accumulation of the PRms (pathogenesis-related maize seed) protein. Light microscopy of trypan blue-stained sections and scanning electron microscopy revealed direct penetration by F. moniliforme hyphae through the epidermal cells of the seedling and colonization of the host tissue by inter- and intracellular modes of growth. Pathogen ingress into the infected tissue was associated with the induction of defense-related ultrastructural modifications, as exemplified by the formation of appositions on the outer host cell wall surface, the occlusion of intercellular spaces, and the formation of papillae. Cellular and subcellular immunolocalization studies revealed that PRms accumulated at very high levels in those cells types that represent the first barrier for fungal penetration such as the aleurone layer of germinating seeds and the scutellar epithelial cells of isolated germinating embryos. A highly localized accumulation of PRms within papillae of the inner scutellar parenchyma cells also occurred, suggesting that signaling mechanisms that lead to the accumulation of PRms in papillae of cell types that are distant from the invading pathogen must operate in the infected maize tissues. Our study also revealed the presence of a large number of fungal cells with an abnormal shape that showed PRms-specific labeling. PRms was found to accumulate in clusters over the fungal cell wall. Taken together, the occurrence of PRms in cell types that first establish contact with the pathogen, as well as in papillae, and in association with fungal cell walls suggests that PRms may have a function in the plant defense response.
摘要 本研究调查了玉米幼苗感染串珠镰刀菌的组织病理学，并与生化宿主防御反应（PRms 蛋白积累）相关联。经台盼蓝染色的切片的光学显微镜和扫描电子显微镜观察显示，串珠镰刀菌菌丝直接穿透幼苗的表皮细胞，并通过细胞间和细胞内生长模式定殖宿主组织。病原体进入感染组织与诱导防御相关的超微结构修饰有关，例如在外宿主细胞壁表面形成附著物、细胞间隙闭塞以及乳突的形成。细胞和亚细胞免疫定位研究表明，PRms 在那些代表真菌穿透的第一道屏障的细胞类型中积累水平非常高，例如萌发种子的糊粉层和分离萌发胚胎的盾片上皮细胞。在内盾片实质细胞的乳突中也高度局部积累了 PRms，这表明导致 PRms 在远离入侵病原体的细胞类型的乳突中积累的信号机制必须在感染的玉米组织中起作用。我们的研究还揭示了大量具有异常形状的真菌细胞的存在，这些细胞表现出 PRms 特异性标记。PRms 被发现聚集在真菌细胞壁上。综上所述，PRms 在与病原体首先建立接触的细胞类型中以及在乳突中积累，并与真菌细胞壁相关联，这表明 PRms 可能在植物防御反应中具有功能。
