Note: This question assumes an earth-like biology.
Could a microbe (probably virus) be created that transformed humans into plants? What I mean by this is that the microbe would take human cells, and slowly, over time, transform them into plant cells. Like the new plant would retain a human like shape, and possibly be a new species of plant, i.e. a human plant. The human (i.e. the human's consciousness) would die in the process, but before the human died he/she would start having plant like tendencies. These would include being attracted to sunlight, drinking lots of water, and eating less food. These new tendencies would lead to the human being a suitable place for a plant to grow, when it eventually created roots and killed its human host. There would be a short stage where both the human and the plant were alive, likely during this stage, the human would not be able to move (lower body would be plant like), and quite possibly would be insane.
So, could such a microbe exist under earth-like biology? And would there be multiple variants of the microbe, with each variant producing a different kind of plant?