N-bands and nucleolus expression in Schistocerca gregaria and Locusta migratoria

Abstract

A new technique is described for simultaneous N-band and nucleoLus identification using acridine orange staining following incubation of chromosome squashes in 50 per cent formamide. This technique, together with silver deposition, has been used to clarify the chromosomal locations of N-bands and nucleolus organisers in the two locust species Schistocerca gregaria and Locusta migratoria. S. gregaria consistently shows interstitial nucleolus organisers in chromosomes L3 and M6 while L. migratoria has telomeric nucleolus organisers in L2 and M6 and an interstital nucleolus organiser in S9 close to the centromere. All nucleolus organisers also N-band and C-band but in addition both species have a large interstitial N-band on chromosome M8 which does not act as a nucleolus organiser. These data are discussed in relation to the mechanism of N-banding, the conflicting reports in the literature of different nucleolus organiser locations in these species and the significance of chromosome regions which N-band but do not act as nucleolus organisers.

Chromosome study in Schistocerca (Orthoptera-Acrididae-Cyrtacanthacridinae): karyotypes and distribution patterns of constitutive heterochromatin and nucleolus organizer regions (NORs)

“…Pairs L2 and M6 showed distal CH blocks and pair S9 presented a proximal block of low staining intensity (Hagele, 1979). Ag-NOR staining revealed two active NORs on the distal region of M6 and on the proximal region of S9 (Fox and Santos 1985), which coincided with rDNA FISH signals (Vaughn et al, 1999). In the present study, S. pallens and S. flavofasciata showed similar patterns of pericentromeric CH distribution, but differed by the presence of small blocks on three mediumSouza and Melo 55 The pericentromeric CH of S. pallens was not entirely stained by the base-specific fluorochromes CMA 3 and DAPI, but small CMA 3 -positive blocks were detected on pairs M4, M5 and M6.…”

“…The interstitial location of AgNORs in S. flavofasciata and S. pallens (rDNA identified by FISH in this species), in contrast to the distal (M6) and proximal NORs (S9) of Schistocerca gregaria (Fox and Santos, 1985), suggest the possible occurrence of inversions including the rDNA loci in the genus.…”

Heterochromatin differentiation between two species of the genus Dociostaurus (Orthoptera: Acrididae)

“…However, these regions are neither always digested with restriction endonucleases whose target only contains G and C, e.g. HaeIII (Gosálvez et at., 1987;Lopez-Fernandez et at., 1989), nor revealed with specific banding techniques such as the N-banding (Fox & Santos, 1985); (ii) both species show pericentromeric heterochromatin which is different both in size and DNA base composition. D. jagoi does not show any response after DA-CMA3 or DAPI, while D. genei with bigger C-bands shows positive response after DAPI in all these regions and DA-CMA3 positive response in some of them.…”

Sex chromosome and autosome divergence in Podisma (Orthoptera) in western Europe

“…This suggests that the chromatin forming these regions is of a special nature (Hagele, 1979;Fox and Santos, 1985;Bella et al, 1986 (Barton and Charlesworth, 1984;Rouhani and Barton, 1987). These different chromosomal forms are currently in contact with each other in some regions and perhaps influence each other's evolution.…”