Abstract
In animals and yeasts, mitochondrial size and number depend not only on mitochondrial division, but also on mitochondrial fusion. However, it is unclear whether mitochondrial fusion also occurs in higher plants. We examined mitochondrial fusion in onion epidermal cells expressing a fusion protein consisting of a fluorescent protein, Kaede, and a mitochondrial pre-sequence. Kaede normally fluoresces green, but after a brief exposure to light at about 350-400 nm, its fluorescence irreversibly changes to red. Using a fluorescent microscope, restricted areas of cells were exposed to UV light, resulting in the co-existence of green and red mitochondria in the same cell. Subsequently, yellow mitochondria were detected, indicating the fusion of red and green mitochondria. In the course of the observation, the average size of mitochondria in a cell did not change. Therefore, in higher plants, mitochondrial division and fusion might also be balanced in a cell.
