Molecular cloning and partial characterization of ribosomal RNA genes from Trypanosoma cruzi

To further analyze the organization of the nuclear rDNA locus in Trypanosoma cruzi, genomic recombinant plasmid clones were constructed and isolated after hybridization with rRNA molecules as hybridization probes. Approximately 11 kilobase pairs from the cistron were cloned in three recombinant plasmids carrying adjacent genomic fragments. Restriction mapping and Southern hybridization experiments performed on these clones indicate the following relative arrangement of the mature rRNA coding sequences: 18S (2.46 kb), S3 (197 b), 24S alpha (2.02 kb), S1 (261 b), 24 beta (1.66 kb), S2 (217 b) and S6 (90 b). Neither S4 (141 b) nor S5 (110 b) sequences were found within these genomic clones. Nevertheless genomic Southerns suggest a linkage of S4 towards the 3' end of this genetic system.