Identification and molecular characterization of R1 transposable elements in the cabbage moth Mamestra brassicae

RFLP experiments showed rDNA variants due to R1 insertions in theMamestra brassicae 28S rDNA genes. Their location within the ribosomal geneswas confirmed by PCR amplification of the 3’ R1-28S rDNA junction. Dot blotting experiments indicated that 10% of rDNA units was interrupted by R1. RTPCR showed that R1 was actively transcribed and that its insertion did not prevent the transcription of the interrupted ribosomal units. Northern blottingindicated that at least a portion of the R1 elements was spliced from the 28SrRNA. Digestion with MspI and HpaII indicated that R1 was not methylated inthe cabbage moth genome and the methylation could be not involved in R1control. These data, as a whole, suggested that M. brassicae R1 was active at thetranspositional level