Generating high variability of B chromosomes in Eyprepocnemis plorans (grasshopper)

Abstract

/n and tDepartamento de Genét/ca, Facultad de B/o/ogIa, Un/vers/dad Comp/utense de Madrid, E-28040 Madrid, Spa/n Twenty-eight progeny analyses (PAs) performed on specimens of E. plorans collected from four natural Iberian populations have been informative about the transmission of rare B chromosome types or the de novo origin of some of them. At least ii rare B-types have been found in addition to the predominant ones: B1 in Daimuz, B2 in Jete and Salobreña, and B5 in Fuengirola. The presence in two controlled crosses of one embryo carrying a B-type which was absent in the parents suggests that these B variants (B20 and B ) have originated de novo. Eleven other PAs suggest that new B derivatives are recurrently arising in these populations. The most frequent B chromosome mutation was centromere misdivision that originated four different B-types (B2m1, B110, B210 and Bmjnj). Other rearrangements were pericentric inversions (B211, B212 and B213), inverse tandem fusion (B211), centric fusion (B11) and deletions (B2d1 and B2d2). The four B derivatives produced by centromeric misdivision are significantly eliminated during sexual transmission, most probably owing to deficiencies in the control of chromosome movement by their hemicentromeres. Those derived from translocations showed Mendelian transmission but deletion B variants showed a tendency to elimination. Our results suggest that B chromosome substitution of B1 by B2 in the Salobreña and Jete populations could be achieved by differences in relative transmission efficiency, as in one controlled cross, where the female carried 1 B1 plus 1 B2, B2 was significantly overtransmitted and B1 eliminated.

B chromosomes in Crustacea Decapoda

“…The largest Bs showed some of the features and behaviour typical of isochromosomes: they are very large and metacentric, with largely symmetrical C-bands in both arms; they often display a folded configuration and in metaphase I they often form univalent rings. Large Bs are present in a few species, among animals they are reported mainly in the Orthoptera (Jones and Rees, 1982), and have been observed more recently in a number of fishes (reviewed in Ziegler et al, 2003).The peculiar features and meiotic behaviour of iso-B chromosomes have been studied in plants (Jones et al, 1989;Santos et al, 1995), in Orthoptera (Hewitt, 1979;Fletcher and Hewitt, 1988;Henriques-Gill et al, 1984;Ló pez-Leó n et al, 1993) and in fishes (Mestriner et al, 2000). Iso-B chromosomes are generated by centromere misdivision and nondisjunction and they can derive from the rearrangement of B chromosomes, as reported in the grasshopper Eyprepocnemis plorans (Ló pez-Leó n et al, 1993) or from an A chromosome as reported in the fish Astyanax scabripinnis (Mestriner et al, 2000).…”

The B chromosome polymorphism of the grasshopper Eyprepocnemis plorans in North Africa: III. Mutation rate of B chromosomes

“…On the basis of morphology and C banding pattern, more than 50 B variants have been described in natural populations of E. plorans (Henriques-Gil et al, 1984;Ló pez-Leó n et al, 1993). The B 1 chromosome was considered the original B in Spanish populations (Henriques-Gil et al, 1984).…”

“…The autosomes may be classified into three size groups: Long (L 1 -L 2 ), Medium (M 3 -M 8 ) and Small (S 9 -S 11 ), the X chromosome size being intermediate between those of L 2 and M 3 . Previous studies have shown that almost all E. plorans populations analysed from the Mediterranean region and the Caucasus show the polymorphism for B chromosomes (Camacho et al, 1980;Henriques-Gil et al, 1984;López-Fernández et al, 1992;Ló pez-Leó n et al, 1993;Cabrero et al, 1997;Bugrov et al, 1999). This polymorphism has revealed the existence of an arms race between A and B chromosomes leading the system through successive stages with B chromosomes passing from parasitic to near-neutral and vice versa, thus facilitating B-polymorphism regeneration (Zurita et al, 1998).…”

“…B chromosomes have been reported in more than 1300 plant and 500 animal species (Jones and Rees, 1982;Jones and Puertas, 1993;Jones, 1995), and Beukeboom (1994) estimated that about 15% of described living beings harbour polymorphisms for B chromosomes. The nature of these chromosomes is heterogeneous, although they are predominantly heterochromatic and show a high variety of morphologies, chromosomal banding patterns and molecular compositions (Henriques-Gil et al, 1984;Green et al, 1987;Green, 1988;Ló pez-Leó n et al, 1993;Bakkali et al, 1999;Cabrero et al, 1999). In Orthoptera, which is the animal group where B chromosome polymorphisms have been more frequently reported (Jones and Rees, 1982), B chromosomes are commonly telocentric, but there are also some iso-B chromosomes originated through centromere misdivision and chromatid nondisjunction, or by centric fusion between two B chromosomes (see López-Leó n et al, 1993).…”

Alteration of the metaphase checkpoint by B chromosomes

“…This species has a widespread polymorphism for B chromosomes that includes more than 40 different variants (Camacho et al, 1980;Henriques-Gil et al, 1984;Henriques-Gil and Arana, 1990;Lopez-Leon et al, 1993). The individuals analyzed in this study carried B5, the most common variant in the central area of the species distribu-tion in Spain, and B1, believed to be the most primitive variant.…”