MICROSATELLITE SEQUENCES ARE UNDER-REPRESENTED IN 2 MITE GENOMES

Microsatellites are known to be a common feature of eukaryote genomes, Here we investigate the presence of microsatellite sequences in the g enome of two mite species, Tetranychus urticae and Amblyseius fallacis , based on screening of both mite genomic libraries and Southern blots of these mites that we compare to two vertebrates. No signal with GT( 15), or a faint smear with CT10 were obtained in Southern analysis for the two mites, whereas both probes strongly bound with vertebrate DNA . Genomic libraries constructed in plasmid and lambda vectors were pro bed and only two CT microsatellites were isolated for T. urticae. Amon g eight trinucleotides probes tested, the strongest hybridization sign al was detected for T. urticae with CAT and TGA probes. These two clas ses of repeats were also the most represented in genomic library scree nings. However, only sequences with short numbers of units could be de tected (<CAT(4) or TGA(9)). Congruency of Southern analysis and screen ing of partial genomic libraries indicates an under-representation of microsatellite sequences in the two mite genomes. The potential of the scarce repetitive DNA isolated from mites to serve as population gene tics markers is discussed on the basis of preliminary assessment of th eir polymorphism.