Cytological modifications in zucchini yellow mosaic virus (ZYMV)-infected Styrian pumpkin plants

The present research demonstrates severe ultrastructural changes induced by zucchini yellow mosaic virus (ZYMV) within the cells of older and younger leaves of Styrian pumpkin plants (Cucurbita pepo L. subsp. pepo var. styriaca GREB.). Cylindrical inclusions (pinwheels), proliferated endoplasmatic reticulum and filamentous viral particles were found throughout the cytoplasm of ZYMV-infected cells and within sieve elements. ZYMV-infection also induced severe modifications in the number and ultrastructure of chloroplasts, whereas mitochondria, nuclei and peroxisomes remained unaffected. A significantly lower number of chloroplasts was observed in all tissues of both ZYMV-infected leaf types when compared to control plants. Statistical quantification revealed that in chloroplasts of ZYMV-infected older and younger leaves the amount of plastoglobuli and starch increased significantly, whereas the amount of thylakoids significantly decreased. The present research gives a more precise insight in ZYMV-induced modifications within single cells and organelles, and provides statistical data of the most affected chloroplasts.