Short Communication A small B chromosome in the grasshopper Ommexecha virens (Ommexechidae).

B chromosomes, also called supernumerary or accessory chromosomes, have been characterized as extra elements found in the karyotypes of different eukaryotic species. B chromosomes are nonvital and only occur in some individuals within a species. Moreover, the chromosomes contain silenced genes, and they exhibit heterochromatinization and the accumulation of repetitive DNA and transposons. In the present study, we describe an extra chromosome in the grasshopper Ommexecha virens for the first time, using conventional staining and fluorescent in situ hybridization techniques, and we discuss the possible origin of the B chromosome.

Physical mapping of the Period gene on meiotic chromosomes of South American grasshoppers (Acridomorpha, Orthoptera).

The single-copy gene Period was located in five grasshopper species belonging to the Acridomorpha group through permanent in situ hybridization (PISH). The mapping revealed one copy of this gene in the L1 chromosome pair in Ommexecha virens, Xyleus discoideus angulatus, Tropidacris collaris, Schistocerca pallens, and Stiphra robusta. A possible second copy was mapped on the L2 chromosome pair in S. robusta, which should be confirmed by further studies. Except for the latter case, the chromosomal position of the Period gene was highly conserved among the four families studied. The S. robusta karyotype also differs from the others both in chromosome number and morphology. The position conservation of the single-copy gene Period contrasts with the location diversification of multigene families in these species. The localization of single-copy genes by PISH can provide new insights about the genomic content and chromosomal evolution of grasshoppers and others insects.

Cytogenetic studies in peripheral blood of bovines afflicted by papillomatosis.

Ten types of bovine papillomavirus (BPV) have been described and there are reports of viral transmission via blood. The presence of viral DNA in lymphocytes was described to be associated with chromosome instability in these cells. This study presents an evaluation of chromosome instability in short-term peripheral lymphocyte cultures from cows presenting skin papillomatosis, compared with asymptomatic infected animals and non-infected healthy bovines. In a total of 2203 cells, 918 (42%) showed at least one chromosome aberration: 42.7 (± 7.8) in animals with papillomatosis (BPV + W), 40.2 (± 11) in asymptomatic animals (BPV-W) and 4 (± 2) in control animals. Significant differences were found between the infected group (with or without symptoms) and the control group (P < 0.0001). The increased frequencies of chromosome aberrations suggest an interaction between the virus and host cell chromatin.

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.

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.

Allozymic characterization and evolutionary relationships in the Brazilian Akodon cursor species group (Rodentia-Cricetidae).

The present study involved an electrophoretic survey of 22 protein loci in 269 individuals belonging to three species of the genus Akodon, A. aff. cursor (2n = 16), A. cursor (2n = 14/15), and A. montensis (2n = 24/25/26), collected in Eastern Brazil. The joint results of gene diversity, genetic distances, phenetic analyses, and phylogenetic trees suggested that A. aff. cursor has recently separated from A. cursor and that the three species have experienced a recent chromosomal divergence followed by low allozyme differentiation. These data are in agreement with their classification as sibling species.

Genetic variation within the Tupi linguistic group: new data on three Amazonian tribes.

A total of 505 individuals belonging to four populations of three Brazilian Indian tribes were variously studied in relation to 34 genetic systems, and the results were compared with South American Indian averages and five other Tupi populations. Rare variants (CdE of the Rh system, PGM211-1, Cp A-CAY1, serum cholinesterase2 C5+ and some Gm combinations) were observed with varying prevalences, and the three tribes showed different degrees of departure (28%-40% of differences of 10% or more in gene frequencies) from South American Indian averages. People from two communities who speak the same language and are labelled as belonging to the same tribe (Asurini) showed a large degree of genetic differentiation. Another of the tribes studied (Urubu-Kaapor) link through genetic distance analyses with two other tribes from the north of the continent, forming a distinct microevolutionary unit. These features emphasize the peculiarities of the genetic variation in populations with a hunter-gatherer, rudimentary agriculture type of economy.

Genetic variation within a linguistic group: Apalai-Wayana and other Carib tribes.

A total of 136 individuals were studied in relation to 31 genetic systems, and the results were compared with South American Indian averages and previous surveys on the Wayana of French Guiana and Surinam. The information was afterwards integrated with data from other Carib groups, and two types of genetic distances (Nei's and Edwards') were calculated a) between five groups, considering ten systems; and b) between nine groups, using five systems. The two measures of genetic distances correlated well (Spearman's correlation coefficient around 0.70), and there was good agreement between the geographical and genetic distances. All analyses indicated a peripheral position for the Apalai-Wayana and their distinctiveness from the Wayana of French Guiana and Surinam, suggesting that intertribal fusions may play an important role in the genetic differentiation of these populations.

Occurrence of a rare variant of superoxide dismutase in Brazil.

During a paternity test performed in Porto Alegre, Brazil, a rare variant of superoxide dismutase, probably SOD A2, was found in a Caucasian child and the putative father. Studies of 1,700 unrelated white individuals from the same and nearby cities had never disclosed such a variant, which was also absent in 2,480 persons of other ethnic groups living in different regions of Brazil. The presence of this rare phenotype in the child and putative father led to the assignment of a very high probability of paternity to the latter.