A 169-base pair tandem repeat DNA marker for subtelomeric heterochromatin and chromosomal rearrangements in aphids of the Myzus persicae group

Numerous copies of a 169-base pair DNA sequence (Myzus persicae group repeat; MpR) occur at subtelomeric locations on all chromosomes of three members of the Myzus persicae species group (Myzus persicae, M. antirrhinii, M. certus), MpR occurs in large tandem arrays at both ends of ail autosomes of the standard 2n = 12 karyotype, and near one end of the X chromosome (the end opposite to the nucleolar organizer) and is estimated to make up about 5% of the genome (a total of about 200 000 copies). Locations of MpR were compared in various karyotypes to determine the likely nature of the rearrangements (fusions, dissociations, translocations) that are found in this species group which, like other Hemiptera, has holocentric chromosomes that are devoid of morphological markers. Aphid clones heterozygous for autosome dissociations do not have any detectable MpR at 'new' chromosome ends, indicating that this sequence is not involved in 'capping' of chromosomes. However, a clone with a de novo autosome fusion had an interstitial block of MPH marking the point of fusion, and clones heterozygous for an autosomal 1,3 translocation had MpR from autosome 1 translocated to a new site on autosome 3. The isolation from M. antirrhinii of the telomeric repeat TTAGG, which is found in several insect groups, is also reported.