Atypical cristae in bundle sheath mitochondria in leaves of Atriplex tatarica (Chenopodiaceae s. str. / Amaranthaceae s. l.)

Electron microscopic analysis of leaf ultrastructure patterns of Atriplex tatarica (Chenopodiaceae s. str. / Amaranthaceae s. l.) revealed a prominent feature in mitochondria in bundle sheath cells (BSCs). Our studies of developing leaves of A. tatarica collected in the Novobilychi neighborhood of Sviatoshyn District (Kyiv City, Ukraine) demonstrated that the internal mitochondrial structure in BS cells is significantly different from that in other cells. Many BSc mitochondria have two types of cristae, normal and atypical ones. The atypical cristae represented with curved lamellae are oriented along the longitudinal axis of a mitochondrion or at some angles to it. Such mitochondria appear to be widely distributed within the BS cells in leaves of A. tatarica and are highly abundant (probably between 70 and 90%), but have not been observed in mitochondria from cells of other chlorenchymal and epidermal tissues. These abnormal mitochondria can only be identified by the presence of atypical cristae; no other differences in their fine structure have been observed. In many cases, such mitochondria are found in close proximity to chloroplasts. A functional connection between the architecture of atypical cristae and their physiological function in BS cells is possible. The close proximity of these mitochondria to chloroplasts indicates that they may play an important role in cellular energy or metabolite transport.