Kinetoplast DNA in the insect trypanosomes Crithidia luciliae and Crithidia fasciculata. I. Sequence evolution and transcription of the maxicircle

Kinetoplast DNA from the insect trypanosome Crithidia luciliae contains a maxicircle of 22 × 10⁶ D. We have cleaved this DNA with endonucleases PstI, XbaI, XhoI, SstI, HaeIII, SalII, HindIII, EcoRI, and HapII and constructed a physical map of the 31 cleavage sites. The maxicircle segments hybridizing with total cellular RNA are clustered on one-half of the maxicircle; the genes for the 9 and 12 S mitochondrial (r)RNAs are located on a 1.7-kb segment. Restriction enzyme analysis indicates a sequence homology of more than 96% between the maxicircles of C. luciliae and C. fasciculata, which is not lower than that found between maxicircles of individual Trypanosoma brucei stocks. We conclude therefore that C. luciliae and C. fasciculata are one species and propose to name this species C. fasciculata and to rename C. luciliae as C. fasciculata, var. luciliae. Furthermore we show that the overall maxicircle genome organization of Crithidia resembles that of Trypanosoma.