Structural and transcriptional features of Bombus terrestris satellite DNA and their potential involvement in the differentiation process.

A unique satellite DNA family was characterized in the genome of the bumble bee, Bombus terrestris. Sequence analysis revealed that it contains two wide palindromes of about 160 and 190 bp, respectively, that span 75% of the repeated unit. One feature of this satellite DNA is that it accounts for different amounts of genomic DNA in males and females. The DNA curvature and bendability were determined by migration on PAGE and by computer analysis. It has been correlated with the presence of dA/dT stretches repeated in phase with the helix turn and with the presence of the deformable dinucleotide CA-TG embedded in some of these A-T-rich regions. Transcription of the satellite DNA was also analyzed by Northern blot hybridization and RT-PCR. Multimeric transcripts spanning several satellite DNA units were found in RNA samples from males, workers, and queens. These transcripts resulted from a specific transcription occurring on one DNA strand in the embryos or on both DNA strands in imagoes. The involvement of DNA curvature in the organization of the satellite DNA and the function of the satellite transcripts is discussed.