Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Original Article Cytogenet Genome Res 119:143–146 (2007) DOI: 10.1159/000109631 Physical mapping of rDNA and satDNA in A and B chromosomes of the grasshopper Eyprepocnemis plorans from a Greek population M. Abdelaziz a M. Teruel a D. Chobanov b J.P.M. Camacho a J. Cabrero a a Departamento de Genética, Universidad de Granada, Granada (Spain) b Institute of Zoology, Bulgarian Academy of Sciences (BAS), Sofia (Bulgaria) In addition to the advantage in transmission (drive), some parasitic B chromosomes show a high rate of muta- tion, thereby frequently generating new B variants, some of which may have increased virulence. The paradigm species, in this respect, is the grasshopper Eyprepocnemis plorans, with more than 50 B variants described in the Iberian Pen- insula, in addition to many others found in other regions. Estimates of the B chromosome mutation rate in both Span- ish (López-León et al., 1993) and Moroccan (Bakkali and Camacho, 2004) populations were around 10 –3 , which is quite high. The combination of drive, its suppression and high mu- tation rate generates a dynamic arms race between A and B chromosomes which, at least in E. plorans, makes up the near-neutral model of B chromosome evolution: a parasitic (driving) B chromosome invades populations swiftly, but A chromosomes evolve B-drive suppression, starting the B on a long run towards near-neutral extinction unless a new parasitic B variant (driving again) emerges in the popula- tion, thus completing a cycle that may repeat indefinitely (Camacho et al., 1997). Abstract. Adult males and females of the grasshopper Eyprepocnemis plorans from a Greek population were anal- ysed by C-banding, silver impregnation and double FISH for two DNA probes, i.e. ribosomal DNA (rDNA) and a 180- bp tandem repeat DNA (satDNA). This population shows characteristics of rDNA location in A chromosomes that are intermediate between those previously reported for eastern (Caucasus) and western (Spain and Morocco) populations. The four rDNA clusters revealed by FISH in chromosomes X, 9, 10 and 11 in Greek specimens imply two more than the two observed in chromosomes 9 and 11 in the Caucasus, but less than the 12 observed in all chromosomes in Morocco. Request reprints from J. Cabrero Departamento de Genética, Universidad de Granada SE–18071 Granada (Spain) telephone: +34 958 243262; fax: +34 958 244073 e-mail: jcabrero@ugr.es © 2007 S. Karger AG, Basel 1424–8581/07/1192–0143$23.50/0 Accessible online at: www.karger.com/cgr Remarkably, the X chromosome bears one of the new rDNA locations in Greece with respect to the Caucasus, but it ap- pears to be inactive, in contrast to X chromosomes in west- ern populations, which are usually active. B chromosomes were very frequent in the Greek population, and three vari- ants differing in size were observed, all of these being large- ly composed of rDNA, with the exception of a small peri- centromeric satDNA cluster. The high B frequency suggests that B chromosomes in this population might behave para- sitically, in resemblance to Bs in western populations. Copyright © 2007 S. Karger AG, Basel B chromosomes are additional chromosomes which, in most cases, behave as genome parasites exploiting the host (A) chromosomes by means of a variety of drive mecha- nisms and frequently causing harmful effects on the organ- ism carrying them. They have been found in about 15% of eukaryotic organisms, thus demonstrating a high evolu- tionary success, and new cases are frequently reported in the literature (for recent reviews see Camacho, 2004, 2005). A genetic conflict between A and B chromosomes is illus- trated by the evolution of drive-suppressing genes in the A chromosomes, as shown for instance in grasshoppers (Shaw and Hewitt, 1985; Herrera et al., 1996), mealybugs (Nur and Brett, 1985), rye (Romera et al., 1991; Jiménez et al., 1997), and maize (González-Sánchez et al., 2003). This study was supported by grants from the Spanish Ministerio de Educación y Ciencia (CGL2006–06307) and Plan Andaluz de Investigación (CVI-165). Manuscript received 22 January 2007; accepted in revised form for publication by M. Schmid, 5 April 2007.