Effects of cerato-platanin, a toxin from Ceratocystis fimbriata f. sp. Platani, on Platanus acerifolia leaves: an ultrastructural study.

Cerato-platanin (CP), a protein previously isolated from the ascomycete Ceratocystis fimbriata f.sp. platani (Cfp), the causal agent of plane canker stain, has been studied with regard its phytotoxic effect in plane leaf cells by transmission electron microscopy. When infiltrated in plane leaf mesophyllum, pure cerato-platanin induced, 24 and 48 h after treatment, several negative responses in palisade and spongy tissues. One of the most important responses consisted, already after 24 h, in a great production of primary starch in these tissues. Moreover, the ultrastructural observations evidenced numerous other symptoms, such as strong alterations in chloroplasts, nuclei and in the cytoplasm. These changes were particularly serious in spongy parenchyma cells. In addition, these cells appeared strongly squashed with a reduced and completely disorganized protoplast.