Molecular cytogenetics in the study of repetitive sequences helping to understand the evolution of heterochromatin in Melipona (Hymenoptera, Meliponini).

The eukaryote genome is enriched by different types of repetitive DNA sequences and is most abundant in heterochromatin regions. Historically, no function has been assigned to these sequences, which makes them the target of studies that have demonstrated their structural and functional importance in the genome. Despite having a constant chromosome number, the genus Melipona has species with wide variation in heterochromatin content, from 8 to 73%, which is an important feature to be investigated regarding its origin and evolution. In the present study, a repetitive DNA sequence of Melipona mondury was isolated by restriction enzyme digestion. This sequence was used to hybridize chromosomes of eight Melipona species that include representatives of the four subgenera and present divergent characteristics in relation to the heterochromatin content. Considering that rDNA localization has shown differences in Melipona, 16 species of this genus were analyzed with 18S rDNA probe. Our data suggest that heterochromatin growth occurred independently in the Michmelia and Melikerria subgenera, considering that the isolated repetitive DNA sequence was shared only by the Michmelia species. Amplification possibly occurred from the centromeric region, causing the displacement of the rDNA sites to the ends of the chromosomes. The repetitive DNA sequence used is a constituent of Michmelia heterochromatin, which that arose from the common ancestor of the species of this subgenus.

Comparative cytogenetics in three Melipona species (Hymenoptera: Apidae) with two divergent heterochromatic patterns.

The genus Melipona is subdivided into four subgenera based on morphological characteristics, and two groups based on cytogenetic patterns. The cytogenetic information on this genus is still scarce, therefore, the goal of this study was to characterize Melipona paraensis, Melipona puncticollis, and Melipona seminigra pernigra using the following techniques: C-banding, DAPI/CMA3 fluorochromes, and FISH with an 18S rDNA probe. Melipona paraensis (2n=18) and M. seminigra pernigra (2n=22) were classified as high heterochromatin content species (Group II). Their euchromatin is restricted to the ends of the chromosomes and is CMA3+; the 18S rDNA probe marked chromosome pair number 4. Melipona puncticollis (2n=18) is a low heterochromatin content species (Group I) with chromosome pair number 1 marked with CMA3 and 18S rDNA. Low heterochromatin content is a putative ancestral karyotype in this genus and high content is not a monophyletic trait (Melikerria presents species with both patterns). Differences concerning the karyotypic characteristics can be observed among Melipona species, revealing cytogenetic rearrangements that occurred during the evolution of this genus. Studies in other species will allow us to better understand the processes that shaped the chromatin evolution in Melipona.

Evidence of ectopic recombination and a repeat-induced point (RIP) mutation in the genome of Sclerotinia sclerotiorum, the agent responsible for white mold.

Two retrotransposons from the superfamilies Copia and Gypsy named as Copia-LTR_SS and Gypsy-LTR_SS, respectively, were identified in the genomic bank of Sclerotinia sclerotiorum. These transposable elements (TEs) contained direct and preserved long terminal repeats (LTR). Domains related to codified regions for gag protein, integrase, reverse transcriptase and RNAse H were identified in Copia-LTR_SS, whereas in Gypsy-LTR_SS only domains for gag, reverse transcriptase and RNAse H were found. The abundance of identified LTR-Solo suggested possible genetic recombination events in the S. sclerotiorum genome. Furthermore, alignment of the sequences for LTR elements from each superfamily suggested the presence of a RIP (repeat-induced point mutation) silencing mechanism that may directly affect the evolution of this species.

Genetic diversity of 'Ubá' mango tree using ISSR markers.

In this study, the genetic diversity of 'Ubá' mango trees cultivated at the Zona da Mata of Minas Gerais State, Brazil, was assessed, to identify whether there is variability in the plants grown in the region, justifying the mass selection as a breeding method. We used 102 accessions. Leaves were collected for extraction of genomic DNA, which was amplified with nine ISSR primers. The data obtained by the analysis of electrophoretic patterns were arranged in a binary matrix, considering 0 for the absence and 1 for the presence of bands. Based on these data, we performed the analysis of genetic dissimilarity and carried out the cluster analysis by the methods of Tocher and graphical dispersion. The most similar accessions are 144 and 150, both coming from Ubá, while the most divergent ones are 29 and 97, from Visconde do Rio Branco. The grouping by the Tocher method separated the accessions into six groups, 94.1% of which were allocated in the first group and showed that there is no separation of accessions depending on the sampling sites. The 3D scatter plot reinforces this conclusion. There is genetic variability among the accessions of 'Ubá' mango tree evaluated. Therefore, it is possible to make mass selection in open-pollinated populations.

Cytogenetic characterization of Partamona cupira (Hymenoptera, Apidae) by fluorochromes.

Four colonies of the stingless bee Partamona cupira (Hymenoptera: Apidae) were cytogenetically analyzed using conventional staining and the fluorochromes CMA(3) e DAPI. The females have 2n = 34 chromosomes (2K = 32 M¯+2 A¯). Some females, however, presented an additional large B acrocentric chromosome, to a total of 2n = 35. Chromosome B and the chromosomal pairs 2, 9 and 10 showed CMA (3) (+) bands, indicating an excess of CG base-pairs. A clear association was verified between the P. helleri B chromosome SCAR marker and the presence of a B chromosome in P. cupira. The data obtained suggests that B chromosomes in P. helleri and P. cupira share a common origin.

Comparative study on the use of specific and heterologous microsatellite primers in the stingless bees Melipona rufiventris and M. mondury (Hymenoptera, Apidae).

Due to their high degree of polymorphism, microsatellites are considered useful tools for studying population genetics. Nevertheless, studies of genetic diversity in stingless bees by means of these primers have revealed a low level of polymorphism, possibly the consequence of the heterologous primers used, since in most cases these were not specifically designed for the species under consideration. Herein we compared the number of polymorphic loci and alleles per locus, as well as observed heterozygosity in Melipona rufiventris and M. mondury populations, using specific and heterologous primers. The use of specific primers placed in evidence the greater frequency of polymorphic loci and alleles per locus, besides an expressive increase in observed heterozygosity in M. rufiventris and M. mondury, thereby reinforcing the idea that populational studies should be undertaken by preferably using species-specific microsatellite primers.

Genetic variability in five populations of Partamona helleri (Hymenoptera, Apidae) from Minas Gerais State, Brazil.

Partamona is a Neotropical genus of stingless bees that comprises 33 species distributed from Mexico to southern Brazil. These bees are well-adapted to anthropic environments and build their nests in several substrates. In this study, 66 colonies of Partamona helleri from five localities in the Brazilian state of Minas Gerais (São Miguel do Anta, Teixeiras, Porto Firme, Viçosa and Rio Vermelho) were analyzed using nine microsatellite loci in order to assess their genetic variability. Low levels of observed (H(o) = 0.099-0.137) and expected (H (e) = 0.128-0.145) heterozygosity were encountered and revealed discrete genetic differentiation among the populations (F (ST) = 0.025). AMOVA further showed that most of the total genetic variation (94.24%) in P. helleri was explained by the variability within local populations.

Genetic variability in five populations of Partamona helleri (Hymenoptera, Apidae) from Minas Gerais State, Brazil

Partamona is a Neotropical genus of stingless bees that comprises 33 species distributed from Mexico to southern Brazil. These bees are well-adapted to anthropic environments and build their nests in several substrates. In this study, 66 colonies of Partamona helleri from five localities in the Brazilian state of Minas Gerais (São Miguel do Anta, Teixeiras, Porto Firme, Viçosa and Rio Vermelho) were analyzed using nine microsatellite loci in order to assess their genetic variability. Low levels of observed (Ho = 0.099-0.137) and expected (He = 0.128-0.145) heterozygosity were encountered and revealed discrete genetic differentiation among the populations (F ST =0.025). AMOVA further showed that most of the total genetic variation (94.24 percent) in P. helleri was explained by the variability within local populations.

Comparative study on the use of specific and heterologous microsatellite primers in the stingless bees Melipona rufiventris and M. mondury (Hymenoptera, Apidae)

Due to their high degree of polymorphism, microsatellites are considered useful tools for studying population genetics. Nevertheless, studies of genetic diversity in stingless bees by means of these primers have revealed a low level of polymorphism, possibly the consequence of the heterologous primers used, since in most cases these were not specifically designed for the species under consideration. Herein we compared the number of polymorphic loci and alleles per locus, as well as observed heterozygosity in Melipona rufiventris and M. mondury populations, using specific and heterologous primers. The use of specific primers placed in evidence the greater frequency of polymorphic loci and alleles per locus, besides an expressive increase in observed heterozygosity in M. rufiventris and M. mondury, thereby reinforcing the idea that populational studies should be undertaken by preferably using species-specific microsatellite primers.

Cytogenetic characterization of Partamona cupira (Hymenoptera, Apidae) by fluorochromes

Four colonies of the stingless bee Partamona cupira (Hymenoptera: Apidae) were cytogenetically analyzed using conventional staining and the fluorochromes CMA3 e DAPI. The females have 2n = 34 chromosomes (2K=32+2). Some females, however, presented an additional large B acrocentric chromosome, to a total of 2n = 35. Chromosome B and the chromosomal pairs 2, 9 and 10 showed CMA3+ bands, indicating an excess of CG base-pairs. A clear association was verified between the P. helleri B chromosome SCAR marker and the presence of a B chromosome in P. cupira. The data obtained suggests that B chromosomes in P. helleri and P. cupira share a common origin.

Genetic divergence between populations of the stingless bee uruçu amarela (Melipona rufiventris group, Hymenoptera, Meliponini): is there a new Melipona species in the Brazilian state of Minas Gerais?

Allozyme, microsatellite and random amplified polymorphic DNA (RAPD) molecular markers were used to investigate the within and between population genetic variability and between population genetic differentiation of the Brazilian stingless bee uruçu amarela (nominally Melipona rufiventris Lepeletier, 1836) present in savanna and Atlantic forest habitats of the Brazilian state of Minas Gerais (MG). We found low levels of within population variability, although there were a large number of private alleles that specifically characterized these populations. The F ST values indicated a high level of genetic diversity between populations. Analysis of molecular variance (AMOVA) showed a high degree of population differentiation between the savanna and Atlantic forest habitats, confirmed by population pairwise F ST data. Principal coordinates analysis and unweighted pair-group method using an arithmetic average (UPGMA) dendrograms also confirmed that in Minas Gerais the savanna populations (M. rufiventris) were genetically distinct from those present in the Atlantic forest (M. mondury). In addition, populations from locations near the towns of Dom Bosco and Brasilândia de Minas were genetically different from those collected in other localities in the savanna. Our data indicate that populations of uruçu amarela found in the savanna and Atlantic forest habitats of Minas Gerais state should be treated separately for conservation purposes and that special attention should be given to the populations found in the region of Dom Bosco and Brasilândia de Minas until their taxonomic status is clarified.

Genetic distance and its association with heterosis in cacao

The efficiency of cacao breeding program can be increased by choosing superior crosses to be made between divergent clones. We assessed the genetic distance among five clones with RAPD data (genetic distance - GD) and with yield component data (Mahalanobis distance - MD). The clones were evaluated in a diallel, during five years, for five yield components. A total of 130 RAPD bands were scored. GD and MD were used to determine the correlation between genetic distances among clones and the performance of their hybrids. The correlation between GD and MD was 0.67 (P=0.03). Both distances were related to heterotic performance of hybrids for wet seed weight/plant and wet seed weight/fruit. The average hybrid performance for the same two yield components was correlated with only MD. Hence, genetic distances measured by RAPD and yield components can be used as a guide to the choice of the superior crosses

Isolation of pectinase hyperproducing mutants of Penicillium expansum

Com o objetivo de obter-se linhagens com maior produçäo de pectinases, Penicillium expansum foi mutagenizado com UV and NTG. Os mutantes selecionados foram analisados quanto à produçäo de enzimas pectinolíticas e comparados com a linhagem parental. Foram obtidos mutantes com aumento de até duas vezes na atividade de Pectina liase ou de Poligalacturonase. O mutante P462 apresenta aumento de 2 vezes na atividade de ambas enzimas