CHEMOTACTIC MOVEMENT TO WOUND EXUDATES AND ATTACHMENT OF AGROBACTERIUM TUMEFACIENS TO SINGLE CELLS AND TISSUES FROM BANANA PLANTS

Recalcitrance of monocotyledonous plants such as banana to Agrobacterium-mediated transformation may be caused by a block in one or more of the following steps: (i) chemotaxis of agrobacteria towards plant cells, (ii) attachment to plant cells, (iii) induction of vir genes, and (iv) transfer and integration of T-DNA into the plant genome. Elaboration of efficient Agrobacterium-mediated transformation for banana requires a systematic evaluation of these steps. The results in the investigation in the first two steps, i.e. chemotaxis and attachment are reported here.

Chemotaxis was studied using a swarm agar plate system which allowed measurement of the bacterial movement towards/backwards test compounds and various intact or wounded banana tissues. Root, corm and leaf tissue from different banana cultivars were tested and all of them were found to be a source of wound exudates able to elicit a positive chemotactic reaction of Agrobacterium. Attachment of Agrobacterium to banana cells and tissues was examined by UV fluorescence microscopy and scanning electron microscopy. These microscopic observations demonstrated the presence of bacteria individually bound or massively attached to the surface of single banana cells and tissues. It can be concluded that at least during the two early steps of interaction A. tumefaciens appears to be compatible with banana indicating the potential for genetic transformation.