Southern analysis of HindIII digested total DNA of individual cockroaches. The blot was probed
with B. germanica rDNA. Individual B. germanica total DNA (lanes 1·) from three different
strains (Jacksonville, Prestage P-6, and Black); only polymorphic hybridization zones are displayed.
In collaboration with Dmitry Mukha, a frequent visiting professor to our lab from the Vavilov Institute of General Genetics (Russian Academy of Sciences), and an expert in rDNA, we have been developing genetic tools for studying population-parameters of B. germanica. Restriction digests of the rDNA repeat unit of the German cockroach reveal significant intraspecies sequence polymorphism, due mainly to structural differences within the non-transcribed spacer regions (NTS) of the ribosomal repeat unit. Dmitry is also comparing the organization, structure, and nucleotide variability of rDNA among families, genera, and species of cockroaches. Our data thus far show that the 5′ end of the 28S rDNA is an informative marker for studies of cockroach phylogeny, while the rDNA internal transcribed spacers (ITS1 and ITS2) are useful for studies of closely related species within Blattella or Periplaneta.
(A) Scheme of the eukaryotic tandemly repeated rDNA clusters; 18S, 5.8S, 28S · corresponding ribosomal RNA genes; ITS1 and ITS2 ·corresponding internal transcribed spacers; NTS ·nontranscribed spacer.
(B) Nucleotide sequence of the Blattella germanica analyzed fragment and primer locations. Main structural elements of the analyzed fragment are indicated using various fonts: 5 fragment of the 28S rDNA ·capital bold; 3 fragment of the 18S rDNA ·capital bold italic; 5.8S rDNA ·lower case bold; ITS1 and ITS2 ·normal capital letters. The boundaries of the described structural elements were defined by comparison with corresponding sequences from GenBank. Sequences corresponding to the primers used for amplification and sequencing (indicated on the right) are underlined.