Localization of HSP single-copy genes by inexpensive, permanent non-fluorescent in situ hybridization on meiotic chromosomes of the grasshopper Schistocerca pallens (Acrididae)

There have been many studies on Schistocerca gregaria and Locusta migratoria, which are important grasshopper pests in many parts of the world. However, the main pest grasshopper species in Brazil, S. pallens, Rhammatocerus schistocercoides and Stiphra robusta, are very poorly characterized genetically. We adapted a permanent in situ hybridization method to extend the genetic characterization of S. pallens by mapping the single-copy genes Hsp70, Hsp83, Hsp27, and Ubi on meiotic chromosomes. Hsp70 was mapped on the L2 chromosome, in which 82% of the signals were observed. Hsp83 was mapped on a medium-sized chromosome, on which 81% of the signals were observed, tentatively identified as M7. The hybridization signals for the Hsp27 gene were detected on the L1 chromosome at a frequency of 58%. The main hybridization site of the Ubi probe was on the L2 chromosome, with 73% of the signals. All mapped genes also presented secondary hybridization signals, always at frequencies below 30%. These are the first single-copy genes mapped for S. pallens and also for the Acrididae family. Since the Acrididae generally present very similar karyotypes, these data are useful as new landmarks for chromosome identification and as a tool for phylogenetic studies on the genus Schistocerca and for comparison with other insects.

Homology of polytene elements between Drosophila and Zaprionus determined by in situ hybridization in Zaprionus indianus

The drosophilid Zaprionus indianus due to its economical importance as an insect pest in Brazil deserves more investigation into its genetics. Its mitotic karyotype and a line-drawing map of its polytene chromosomes are already available. This paper presents a photomap of Z. indianus polytene chromosomes, which was used as the reference map for identification of sections marked by in situ hybridization with gene probes. Hybridization signals for Hsp70 and Hsr-omega were detected, respectively, in sections 34B and 32C of chromosome V of Z. indianus, which indicates its homology to the chromosomal arm 3R of Drosophila melanogaster and, therefore, to Muller's element E. The main signal for Hsp83 gene probe hybridization was in section 17C of Z. indianus chromosome III, suggesting its homology to arm 3L of D. melanogaster and to element D of Muller. The Ubi probe hybridized in sections 10C of chromosome II and 17A of chromosome III. Probably the 17A is the polyubiquitin locus, with homology to arm 3L of D. melanogaster and to the mullerian D element, as suggested also by Hsp83 gene location. The Br-C gene was mapped in section 1D, near the tip of the X chromosome, indicating its homology to the X chromosome of D. melanogaster and to mullerian element A. The Dpp gene probe hybridized mainly in the section 32A of chromosome V and, at lower frequencies to other sections, although no signal was observed as expected in the correspondent mullerian B element. This result led to the suggestion of a rearrangement including the Dpp locus in Z. indianus, the secondary signals possibly pointing to related genes of the TGF-beta family. In conclusion, the results indicate that chromosomes X, III, V of Z. indianus are respectively correspondents to elements A, D, and E of Muller. At least chromosome V of Z. indianus seems to share synteny with the 3R arm of D. melanogaster, as indicated by the relative positions of Hsp70 and Hsr-omega, although the Dpp gene indicates a disruption of synteny in its distal region.