In vitro cellular division of trypanosoma abeli reveals two pathways for organelle replication

Abstract

Since the observation of the great pleomorphism of fish trypanosomes, in vitroculture has become an important tool to support taxonomic studies investigat-ing the biology of cultured parasites, such as their structure, growth dynamics,and cellular cycle. Relative to their biology, ex vivo and in vitro studies haveshown that these parasites, during the multiplication process, duplicate andsegregate the kinetoplast before nucleus replication and division. However,the inverse sequence (the nucleus divides before the kinetoplast) has onlybeen documented for a species of marine fish trypanosomes on a single occa-sion. Now, this previously rare event was observed inTrypanosoma abeli,afreshwater fish trypanosome. Specifically, from 376 cultured parasites in themultiplication process, we determined the sequence of organelle division for111 forms; 39% exhibited nucleus duplication prior to kinetoplast replication.Thus, our results suggest that nucleus division before the kinetoplast may notrepresent an accidental or erroneous event occurring in the main pathway ofparasite reproduction, but instead could be a species-specific process of cellbiology in trypanosomes, such as previously noticed forLeishmania. This "al-ternative" pathway for organelle replication is a new field to be explored con-cerning the biology of marine and freshwater fish trypanosomes.