Histopathology of Chloroplast Ultrastructure and Inclusion Bodies in CMV-Infected Plant Tissues Using Electron Microscopic Examination and ImageJ Analysis

Histopathology of Chloroplast Ultrastructure and Inclusion Bodies in CMV-Infected Plant Tissues Using Electron Microscopic Examination and ImageJ Analysis

Cucumber mosaic virus (CMV) is an economically important virus that causes wide-spread diseases damaging crops worldwide. Two strains of the virus were detected using ELISA with specific antibodies, and isolated from Kuwait environment designated CMVKU1 and CMV-KU2. The KU1 is a mild strain and is associated with a benign viral satellite RNA, while KU2 isolate, is a severe strain and lacking viral satellite RNA. Both strains were used in a comparative study to investigate the effects of CMV infection on the ultrastructure of chloroplasts and inclusion bodies in test plants of tomato (Lycopersicon esculentum) and squash (Cucurbita pepo). Transmission electron microscopy (TEM) was used to determine the extent of infection and damage caused by virus isolates on chloroplast structure, and cellular inclusions including plastoglobules, and starch granules. Chloroplasts, the photosynthetic apparatus of plants, in infected tissues were severely affected with KU2 strain that caused a reduction and damage of their main structure, number, size, and inclusion bodies compared to the benign strain of KU1 and healthy control plants. Electron micrographs of ultra-thin sections proved the presence of the viral nanoparticles. The formation of viral crystalline bodies, chloroplast damage and malformation due to the viral infection. As the infection progressed, chloroplasts were destroyed and grana were disorganized and scattered into the cytoplasm that causes reduction in chlorophyll contents in plant tissues. ImageJ freeware analysis were used to determine the extent of infection and host-virus interactions and damage caused by virus isolates...