Studies on Cytopathology of Viroid Infections

本研究旨在描述在类病毒感染细胞中发生的细胞病变过程，并证明类病毒感染特有的发病机制。利用柑橘外皮类病毒（CEVd）、啤酒花特技病毒（HSVD）和苹果疤痕皮类病毒（ASSVd），获得了以下结果：cevd感染番茄叶片细胞的病理变化。顶叶小叶严重皱褶，细胞壁起伏，叶绿体解体，线粒体解体等。第5叶的小叶有轻微的卷曲症状，而无特异性症状。hsv感染啤酒花树脂腺的细胞病变。在啤酒花植物中，已经形成了两种树脂腺体，即圆盘状腺体和杯状腺体。典型的细胞壁扭曲和亚细胞细胞器的破坏主要观察到感染的腺体分泌细胞。此外，在感染的细胞中，树脂物质（α -酸）不能完全释放到皮下空间，因此杯子不能充满晶格状结构，提示α -酸的细胞外分泌减少。asvd侵染苹果果皮的细胞病变。果皮（表皮和下皮层）的细胞形状。细胞严重扭曲，细胞壁起伏不定，厚度不规则。在下皮层，果胶物质不能积聚到细胞间隙中。从而导致皮下细胞变平。待总结。上述结果表明，叶片细胞、分泌细胞和果皮细胞的细胞壁变形一致导致细胞骨架结构变形的顺序过程，而细胞骨架结构变形是类病毒感染的结果。

The present study was undertaken to describe the cytopathic processes occurring in viroid-infected cells and to demonstrate the mechanism of pathogenesis specific to viroid infection. By using citrus exocortis viroid (CEVd), hop stunt viroid (HSVD) and apple scar skin viroid (ASSVd), following results are obtained.1. Cytopathic changes in CEVd-infected tomato leaf cells.Leaflets on terminal leaves bearing severe rugosity showed the undulated cell wall, disorganization of chloroplasts, mitochondrial disintegration etc. In the leaflets on 5th leaf bearing mild curling symptom, however, no specific symptoms were observed.2. Cytopathic changes in HSVd-infected resin glands of hops.In hop plants, there have been formed two kinds of resin glands, i. e., disk-shaped gland and cup-shaped gland. Typical cell wall distortion and disorganization of subcellular organella were predominatly observed in the infected secretory cells of both the glands. Moreover, it was evident in the infected cells that resinous substance (alpha acid) could not fully liberated into subcuticular space, thus the cup could not filled with lattice-like structure, suggesting the decrease in extracellular secretion of alpha acid.3. Cytopathic changes in ASSVd-infected fruit skin of apple.The cell shapes of fruit skin (epidermis and hypodermal layers) of the infected apple fruit (cv. Indo) were severely distorted and their cell walls were undulated with irregular thickness. In the hypodermal layers, it was noticeable that pectic substances could not accumulated into the intercellular space. thus resulting in the flattened hypodermal cells.4. To be summarized.The results mentioned above indicated to suggest that cell wall distortion in the leaf cells, secretory cells and fruit skin cells consistently leads to the sequential processes of the structural deformation of cell skeltones which are disturbed as a consequence of viroid infection.