An AT-rich satellite DNA sequence, E180, in alfalfa (Medicago sativa)

A DNA fragment of approximately 750 bp was cloned from EcoRI-digested nuclear DNA of alfalfa (Medicago sativa). Southern blot and sequence analysis showed that the cloned DNA fragment represents a tetramer of a highly tandemly repeated DNA sequence of 185-188 bp (E180). The consensus sequence deduced from the four repeating units is 189 bp in length with an AT content of 67%. The copy number of the satellite DNA was estimated to be approximately 1.8 x 10(5) per genome and constitutes about 1% of the alfalfa genome. Sequence comparison revealed no identity to any repetitive DNA sequences that have been published to date. Digestion with HpaII and MspI indicated a high degree of methylation at the internal C of the restriction site CCGG within E180.