kinetoplast

The kinetoplast is the single, organized mitochondrial DNA network found in kinetoplastid protists, a distinctive feature of this group. It resides inside the single, large mitochondrion and is visible as a dense disk-shaped structure called the kinetoplast. The network consists of two classes of circular DNA molecules: thousands of minicircles and a smaller number of maxicircles. Minicircles encode guide RNAs required for RNA editing, while maxicircles carry typical mitochondrial genes such as rRNAs and protein-coding transcripts; however, many transcripts require uridine insertion/deletion editing guided by the minicircle-encoded gRNAs.

The kinetoplast is physically connected to the flagellum-bearing basal body via the tripartite attachment complex, linking kDNA to cellular architecture. This arrangement coordinates replication and segregation of the kDNA during cell division. In the replication cycle, minicircles are released from the network, replicated as free circles, and then reattached to the network; maxicircles duplicate within the network in concert with overall kDNA replication. The network is partitioned between daughter cells during cytokinesis, ensuring inheritance by both progeny.

Kinetoplast DNA is essential for mitochondrial function in these organisms. Disruption of kDNA replication or RNA editing can be lethal. Organisms that possess a kinetoplast include Trypanosoma and Leishmania species, as well as related genera such as Crithidia and Bodo. The kinetoplast, together with the basal body and flagellum, is a hallmark of the kinetoplastid lineage and a major focus of research on RNA editing and mitochondrial biology in protists.