Copy number of P elements, KP/full-sized P element ratio and their relationships with environmental factors in Brazilian Drosophila melanogaster populations

The P transposable element copy numbers and the KP/full-sized P element ratios were determined in eight Brazilian strains of Drosophila melanogaster. Strains from tropical regions showed lower overall P element copy numbers than did strains from temperate regions. Variable numbers of full-sized and defective elements were detected, but the full-sized P and KP elements were the predominant classes of elements in all strains. The full-sized P and KP element ratios were calculated and compared with latitude. The northernmost and southernmost Brazilian strains showed fewer full-sized elements than KP elements per genome, and the strains from less extreme latitudes had many more full-sized P than KP elements. However, no clinal variation was observed. Strains from different localities, previously classified as having P cytotype, displayed a higher or a lower proportion of KP elements than of full-sized P elements, as well as an equal number of the two element types, showing that the same phenotype may be produced by different underlying genomic components of the P-M system

Characterization of hobo element copy number and integrity in Brasilian populations of Drosophila melanogaster

We have determined the copy number and the presence of full-size hobo transposable elements in eight Brasilian strains of Drosophila melanogaster. Genomic DNA was digested with AvaII and XhoI restriction enzymes, respectively, and probed with a 963 bp sequence of the hobo element. Variable numbers of full-sized and defective elements were detected in all strains. The range of the copy number was 22.13 +/- 4.52. Blots showed the presence of a 2.6 kb fragment, corresponding to the complete element, in all strains exception of one and the 1.0 kb sequence, correponding to the Th1 and Th2 repressor elements. There was neither association among copy numbers of hobo elements and latitude nor the mean annual temperatures in the original geographical region of each strain

Drosophila melanogaster P transposable elements: mechanisms of transposition and regulation

The molecular mechanisms that control P element transposition and determine its tissue specificity remain incompletely understood, although much information has been compiled about this element in the last decade. This review summarizes the currently available information about P element transposition, P-M hybrid dysgenesis and P cytotype features, P element-encoded repressors, and regulation of transposition

Identification of two subfamilies of micropia transposable element in species of the repleta group of Drosophila

The occurrence, number of insertion sites and antisense RNA expression of micropia transposable element were studied in 26 species that belong to three subgroups (mercatorum, mulleri and hydei) of repleta group of Drosophila. Under high specific PCR, micropia sequences were detected in 11 species, but under less stringent condition, this retrotransposon was detected in all species. The widespread distribution of micropia suggests that this element was already present at the common ancestor of the repleta group of Drosophila. Southern blot analysis showed a variation from 0 to 17 different insertion sites and the occurrence of male-specific sequences. We found that the expression of the 1.0 kb micropia antisense RNA is variable among the species and tissues (soma and testis), which suggests that more than one mechanism regulates transposition in these species. Variation of amplification by PCR and of antisense RNA expression, as well as divergence of nucleotide sequences among the species allow us to suggest that at least two subfamilies of micropia transposable element are harbored by the genome of this species group

P elements in the saltans group of Drosophila: a new evaluation of their distribution and number of genomic insertion sites

Few are studies on P elements that have addressed the saltans group. These studies had shown that species from the cordata and elliptica subgroups were devoid of any discernible P homologous sequences, while species from the parasaltans, sturtevanti, and saltans subgroups all contain P element sequences. Our analyses showed the presence of one to 15 P element insertion sites in species of the saltans group, including Drosophila neocordata and Drosophila emarginata (cordata and elliptica subgroups, respectively). From these species, only those from the parasaltans, sturtevanti, and saltans subgroups harbor canonical P elements and, only those of the last two subgroups seem to harbor putative full-sized elements. Due to the low similarity of the sequences found in D. neocordata and D. emarginata to those earlier described, we suggest that these sequences might be rudimental P element derivatives that were present in the ancestral of the subgenus Sophophora. (C) 2004 Elsevier B.V. All rights reserved

Characterization of esterases in a Brazilian population of Zaprionus indianus (Diptera : Drosophilidae)

The aim of this study was to characterize esterases in Zaprionus indianus, a drosophilid recently introduced into Brazil. A further aim was study the variation of activity of esterases in the presence of inhibitors and their expression according to sex, sexual activity and age of individual flies. Polymorphisms were detected in two esterase loci (Est-2 and Est-3) and monomorphisms in four others (Est-1, Est-4, Est-5 and Est-6). Biochemical tests using alpha- and beta-naphthyl acetate and the inhibitors malathion, eserine sulphate and PMSF allowed us to classify EST-2 and EST-5 as beta-esterases, both carboxyl-esterases, and EST-1, EST-3, EST-4 and EST-6 as alpha-esterases. EST-1 and EST-3 were classified as carboxyl-esterases and EST-4 and EST-6 as cholinesterases. EST-5 activity was more pronounced in males and EST-2 was restricted to them or to recently copulated females. EST-4, rarely detected, was not characterized. Based on their biochemical characteristics possible roles for these enzymes are suggested

Evaluation of fitness components in strains of Drosophila mulleri carrying different genotypes for an esterase

Several fitness components in strains of Drosophila mulleri carrying the slow or the fast alleles for the major beta esterase (esterase-4) found in this species, as well as in heterozygous flies in which the slow or fast alleles came from one of the parents, were evaluated. Twelve components were analysed including longevity of both virgins and mated males and females, productivity, viability, including the egg-larva, egg-pupa, egg-imago and pupa-imago periods. These parameters were used to estimate the total fitness for each genotype. The best score was reached by individuals having the Est-4(S)/Est-4(S) genotype (scored at 1.000), followed by a fitness value of 0.892 presented by the Est-4(F)/Est-4(S) genotype (with the fast allele from maternal origin), 0.863 for the Est-4(F)/Est-4(F) and 0.842 for the Est-4(S)/Est-4(F) genotypes (with Est-4(F) maternal origin). These results suggested a higher relative adaptability of the Est-4(S)/Est-4(S) genotype followed by the Est-4(F)/Est-4(S) hybrid that possessed the allele Est-4(S) of maternal origin, which was incompatible with predictions of neutral polymorphism

Transposable elements in Coffea (Gentianales : Rubiacea) transcripts and their role in the origin of protein diversity in flowering plants

Transposable elements are major components of plant genomes and they influence their evolution, acting as recombination hot spots, acquiring specific cell functions or becoming part of protein-coding regions. The latter is the subject of the present analysis. This study is a report on the annotation of transposable elements (TEs) in expressed sequences of Coffea arabica, Coffea canephora and Coffea racemosa, showing the occurrence of 383 ESTs and 142 unigenes with TE fragments in these three Coffea species. Based on selected unigenes, it was possible to suggest 26 putative proteins with TE-cassette insertions, demonstrating a likely contribution to protein variability. The genes for two of those proteins, the fertility restorer (FR) and the pyrophosphate-dependent phosphofructokinase (PPi-PFKs) genes, were selected for evaluating the impact of TE-cassettes on host gene evolution of other plant genomes (Arabidopsis thaliana, Oryza sativa and populus trichocarpa). This survey allowed identifying a FR gene in O. sativa harboring multiple insertions of LTR retrotransposons that originated new exons, which however does not necessarily mean a case of molecular domestication. A possible transduction event of a fragment of the PPi-PFK beta-subunit gene mediated by Helitron ATREPX1 in Arabidopsis thaliana was also highlighted.279438540

Testing transposable elements as genetic drive mechanisms using Drosophila P element constructs as a model system

The use of transposable elements (TEs) as genetic drive mechanisms was explored using Drosophila melanogaster as a model system. Alternative strategies, employing autonomous and nonautonomous P element constructs were compared for their efficiency in driving the ry(+) allele into populations homozygous for a ry(-) allele at the genomic rosy locus. Transformed flies were introduced at 1%, 5%, and 10% starting frequencies to establish a series of populations that were monitored over the course of 40 generations, using both phenotypic and molecular assays. The transposon-borne ry(+) marker allele spread rapidly in almost all populations when introduced at 5% and 10% seed frequencies, but 1% introductions frequently failed to become established. A similar initial rapid increase in frequency of the ry(+) transposon occurred in several control populations lacking a source of transposase. Constructs carrying ry(+) markers also increased to moderate frequencies in the absence of selection on the marker. The results of Southern and in situ hybridization studies indicated a strong inverse relationship between the degree of conservation of construct integrity and transposition frequency. These finding have relevance to possible future applications of transposons as genetic drive mechanisms