Cloning and Sequence Analysis of 5S Ribosomal RNA Gene(s) and Associated Intergenic Spacer Regions in Carica Species

The 5S ribosomal RNA gene(s) and their associated intergenic spacer regions were amplified from Carica papaya and Carica quercifolia by polymerase chain reaction. Both Carica species exhibited differently sized amplification products. Sequence analysis of these PCR products revealed that the 5S rRNA genes are arranged as tandem repeats in these regions. Sequence data revealed that the 5S rRNA gene from Carica quercifolia was 119 bp in length. Sequence variation was observed in various 5S rRNA gene copies cloned from Carica quercifolia. Only truncated 5S rRNA gene but with its full spacer region was recovered from Carica papaya. Interestingly, intergenic spacer sequence cloned from Carica papaya contained two specific domains, a 30bp “CT” rich domain exhibiting 95-100% homology to several human chromosomes and a domain matching with mitrocomin precursor, a photoprotein from Mitrocoma cellularia. The role of 5S rRNA gene and their spacer regions in discerning the germplasm and in adaptation of the species is discussed.