Silene latifolia and Microbotryum violaceum : Molecular, cellular and Morphological studies on plant sexuality and parasitic fungus operating it.

雌雄异株植物宽叶银杏雌花中雄性器官的发育是通过侵染黑穗病真菌紫罗兰诱导的。健康雌花的雄蕊只发育到第6期，而感染的雌花雄蕊发育到成熟期(第12期)，雄蕊中充满了真菌的冬孢子而不是花粉粒。利用自然扫描电子显微镜、诺马尔斯基干涉显微镜和荧光显微镜，我们研究了这种寄生对寄主植物的形态改变和黑粉菌丝在花蕾中的定位。受感染植株的花寿命明显长于健康植株，这可能是因为感染加强了花器官，如花基和花药花丝。病株幼芽各器官均可观察到黑穗病菌丝，包括药片、花瓣、雄蕊和雌蕊原基。在健康的女性…较多的花，花药启动了造孢细胞的形成，但缺乏壁细胞层。相反，与健康雄花的花药一样，受感染的雌花的顶细胞层分化为绒毛组织、中间细胞层和内壁特异层。在感染的花药中，黑穗病孢子的形成始于造孢细胞之间的胞间区域，导致未成熟的造孢细胞、绒毡层组织和中间细胞层的退化。为了研究寄主与寄主之间的相互作用，用高压冷冻固定法对感染雌花的幼蕾和真菌诱导的花药进行了电子显微镜观察。利用这种方法，我们发现该真菌的寄生菌丝含有多个胞外小泡，并具有一致的外观，直到第8期。在感染的雌性花药中，寄生菌丝在死亡的造孢细胞附近被观察到。在第9期，观察到大量死亡和死亡的造孢细胞，其中真菌的造孢菌丝发育并形成初始冬孢子。在这个阶段，一些真菌附近存在几种类型的电子致密物质。最初的冬孢子含有两种类型的液泡，银蛋白染色显示真菌细胞壁含有丰富的碳水化合物。产孢细胞可能对真菌的感染很敏感，从而导致破坏。此外，这种真菌加速了花药中细胞的死亡，并利用死亡寄主细胞的成分形成成熟的冬孢子。宽叶硅烯是一种雌雄异株植物，其性别由X和Y染色体决定。用原位杂交技术检测了拟南芥中雌蕊(P1)的同源基因SLM2的表达。SLM2在受抑制的雌花雄蕊中不表达，但在受黑穗病侵染的雌花雄蕊中表达。这些结果表明，SLM2的控制与Y染色体的存在无关。感染黑穗病的雌性为阐明B功能基因和性别决定因素之间的关系提供了一个有用的系统。较少

The development of male organs is induced in female flowers of the dioecious plant Silene latifolia by infection with the smut fungus Microbotryum violaceum. Stamens in a healthy female flower grow only to stage 6, whereas those in an infected female flower develop to the mature stage (stage 12), at which the stamens are filled with fungal teliospores instead of pollen grains.Using natural scanning electron microscopy, Nomarski interference microscopy, and fluorescence microscopy, we investigated the morphological modifications of the host plant resulting from this parasitism and the localization of smut hyphae in the flower bud. Flowers of infected plants lasted significantly longer than those of healthy plants, probably because the infection strengthened floral organs, such as the flower base and the anther filaments. Smut hyphae were observed throughout all organs of the young flower buds of infected plants, including sepals, petals, stamens, and pistil primordia. In healthy female … More flowers, anthers initiated sporogenous cell formation, but lacked parietal cell layers. By contrast, the parietal cell layers of infected female flowers differentiated into tapetal tissue, middle cell layers, and endothecial layers, as in the anthers of healthy male flowers. Smut spore formation in the infected anther was initiated in intercellular regions between the sporogenous cells, resulting in degeneration of premature sporogenous cells, tapetal tissue, and middle cell layers. The development of the endothecial layers and epidermis in the infected anther were morphologically normal.To investigate these host-parasite interactions, young floral buds and fungus-induced anthers of infected female flowers were examined by electron microscopy following fixation by a high-pressure freezing method. Using this approach, we found that parasitic hyphae of this fungus contain several extracellular vesicles and have a consistent appearance up to stage 8. At that stage, parasitic hyphae are observed adjacent to dying sporogenous cells in the infected female anther. At stage 9, an increased number of dead and dying sporogenous cells is observed, among which the sporogenous hyphae of the fungus develop and form initial teliospores. Several types of electron-dense material are present in proximity to some fungi at this stage. The initial teliospores contain two types of vacuoles, and the fungus cell wall contains abundant carbohydrate, as revealed by silver protein staining. The sporogenous cell is probably sensitive to infection by the fungus, resulting in disruption. In addition, the fungus accelerates cell death in the anther and utilizes constituents of the dead host cell to form the mature teliospore.Silene latifolia is a dioecious plant in which sex is determined by X and Y chromosomes. Expression of the B-function gene SLM2, an ortholog of PISTILLATA (P1) in Arabidopsis, was examined by in situ hybridization. SLM2 was not expressed in suppressed stamens of female flowers, but was expressed in developing stamens of smut-infected female flowers. These results indicate that the control of SLM2 is independent of the presence of the Y chromosome. Smut-infected females provide a useful system for clarifying the relationship between the B-function gene and the sex determination factor. Less