Isolation of a new germ line-specific repetitive DNA family in <i>Acricotopus</i> by microdissection of polytenized germ line-limited chromosome sections from a permanent larval salivary gland preparation

Abstract

In Acricotopus lucidus (Diptera, Chironomidae) the germ line-limited chromosomes (Ks) have developed from the soma chromosomes (Ss) by endoreduplication, rearrangements and accumulation of germ line-specific repetitive sequences. For molecular analysis of specific small K sections, microdissection of metaphase Ks generally yields very limited amounts of DNA. In this study, K-specific DNA was microdissected from defined polytenized K sections of X-ray induced K-S-rearrangements of permanent salivary gland chromosome preparations and was then amplified by DOP-PCR. A new germ line-specific tandem repetitive DNA family was isolated by this way from a heterochromatic K segment, characterized and localized on the Ks by FISH. The repetitive elements are related to sequences of earlier described K-specific tandem repetitive DNA families in A. lucidus, but are located mainly in terminal heterochromatin bands of the two largest Ks and only to a limited degree in the paracentromeric K heterochromatin. This demonstrates that a collection of permanent preparations of K-S-rearrangements with polytenized heterochromatic and S-homologous K sections of A. lucidus can be used as a source for obtaining K sequences of defined K parts to investigate the molecular evolution of the Ks.

Satellite DNA in insects: a review

“…The Ks consist of large S-homologous sections and of heterochromatic segments with a germ line-specific repetitive DNA family. It has been suggested that these sequences may have importance in the germ line-soma segregation processes, probably by acting as enzymatic signals for the recognition of both lines (Staiber, 2002(Staiber, , 2004(Staiber, , 2006.…”

Cytogenetic Analysis of Partial Elimination of Germ Line Limited Chromosomes from Primary Germ Cells in Acricotopus lucidus (Diptera, Chironomidae)

“…2a using painting probes of the three Ss (SI, blue; SII, red; SIII, green) also clearly demonstrates that the Ks are descendants of the Ss and are composed of large (painted) S-homologous sections and of heterochromatic segments (Fig. 2b) containing germ line specific repetitive sequences (Staiber andSchiffkowski 2000, Staiber 2002).…”

“…1a-n) (Bauer andBeermann 1952, Bauer 1970). This reduction in the number of Ks is compensated in the last socalled differential gonial mitosis by a migration of the unseparated Ks to only one cell pole (Staiber 1994) as shown in Fig. 2a, b.…”

“…The origin and the structural evolution of the Ks of the orthocladiid Acricotopus lucidus were investigated by chromosome painting of mitotic and meiotic metaphases using specific probes of the Ss (Staiber andSchiffkowski 2000, Staiber andWahl 2002). The painting results clearly demon-strated that the Ks are descendants of the Ss and possess large S-homologous sections in addition to heterochromatic segments containing germ line specific repetitive sequences.…”

“…Nothing is known about the mechanism discriminating between the half of the Ks that are eliminated, and the half that segregate regularly. In Acricotopus, a G-banding study of K complements of gonial cell showed after elimination mitosis that the K complements vary in number and composition of the nine different K types within one and between different larvae (Staiber 1988).…”