RESUMEN
The olive fly, Bactrocera oleae, is the key pest on olives in the Mediterranean area. The pest can destroy, in some cases, up to 70% of the olive production. Its control relies mainly on chemical treatments, sometimes applied by aircraft over vast areas, with their subsequent ecological and toxicological side effects. Bacillus thuringiensis is a spore-forming soil bacterium which produces a protein crystal toxic to some insects, including the orders of Lepidoptera, Diptera, and Coleoptera and other invertebrates. The aim of this study was to search for isolates toxic to B. oleae. Several hundred B. thuringiensis isolates were obtained from olive groves and olive presses in different areas of Greece, Sardinia (Italy), and Spain and from cooperating scientists throughout the world. Some isolates were found toxic only to adults or larvae and some to both stages of the olive fly. In addition, the most toxic isolates were assayed on Opius concolor Szepl. (Hym. Braconidae), the most important parasitoid of the olive fruit fly. Only 3 isolates out of 14 gave significant mortality against this parasitoid. Several of the most toxic crystalliferous isolates may contain novel toxins since they gave no PCR products when probed with primers specified for 39 known toxin genes.
Asunto(s)
Bacillus thuringiensis , Dípteros/microbiología , Larva/microbiología , Animales , Bacillus thuringiensis/aislamiento & purificación , Proteínas Bacterianas/genética , Cartilla de ADN , Reacción en Cadena de la Polimerasa , TemperaturaRESUMEN
The study of gypsy elements in Drosophila subobscura (gypsyDs) indicated that they are transcriptionally active and mobile. From the comparative analysis of a complete gypsyDs element with the canonical gypsy sequence from D. melanogaster (gypsyDm) it can be deduced that while the whole structure is maintained, the gypsyDs ORF3 encodes a non-functional Env protein. The PCR amplification and sequencing of the ORF3 from different laboratory strains and H271 clones show that all gypsyDs sequences studied have frame-shifting mutations in this region. These results support that gypsyDs elements lack functional Env proteins and consequently they lack infective ability. In this way, it can be proposed that gypsyDs elements are degenerate forms of insect retroviruses. Heterogeneous results have been obtained in the study of the presence of gypsyDm sequences in different D. subobscura strains indicating that these sequences are unstable in this species.
Asunto(s)
Drosophila/genética , Retroelementos , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Datos de Secuencia Molecular , Estructura Terciaria de Proteína , Retroviridae/genética , Homología de Secuencia de Aminoácido , Homología de Secuencia de Ácido NucleicoRESUMEN
We have determined the nucleotide sequence of a 7.5 kb full-size gypsy element from Drosophila subobscura strain H-271. Comparative analyses were carried out on the sequence and molecular structure of gypsy elements of D.subobscura (gypsyDs), D.melanogaster (gypsyDm) and D.virilis (gypsyDv). The three elements show a structure that maintains a common mechanism of expression. ORF1 and ORF2 show typical motifs of gag and pol genes respectively in the three gypsy elements and could encode functional proteins necessary for intracellular expansion. In the three ORF1 proteins an arginine-rich region was found which could constitute a RNA binding motif. The main differences among the gypsy elements are found in ORF3 (env-like gene); gypsyDm encodes functional env proteins, whereas gypsyDs and gypsyDv ORF3s lack some motifs essential for functionality of this protein. On the basis of these results, while gypsyDm is the first insect retrovirus described, gypsyDs and gypsyDv could constitute degenerate forms of these retroviruses. In this context, we have found some evidence that gypsyDm could have recently infected some D.subobscura strains. Comparative analyses of divergence and phylogenetic relationships of gypsy elements indicate that the gypsy elements belonging to species of different subgenera (gypsyDs and gypsyDv) are closer than gypsy elements of species belonging to the same subgenus (gypsyDs and gypsyDm). These data are congruent with horizontal transfer of gypsy elements among different Drosophila spp.
Asunto(s)
Drosophila/genética , Retroelementos/genética , Retroviridae/genética , Proteínas Virales/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Clonación Molecular , Drosophila/metabolismo , Datos de Secuencia Molecular , Retroviridae/metabolismo , Alineación de Secuencia , Análisis de SecuenciaRESUMEN
Characterization of sequences homologous to the Drosophila melanogaster gypsy transposable element was carried out in Drosophila subobscura (gypsyDS). They were found to be widely distributed among natural populations of this species. From Southern blot and in situ analyses, these sequences appear to be mobile in this species. GypsyDS sequences are located in both euchromatic and heterochromatic regions. A complete gypsyDS sequence was isolated from a D. subobscura genomic library, and a 1.3-kb fragment which aligns with the ORF2 of the D. melanogaster gypsy element was sequenced. Comparisons of this sequence in three species (D. subobscura, D. melanogaster, and D. virilis) indicate that there is greater similarity between the D. subobscura-D. virilis sequences than between D. subobscura and D. melanogaster. Molecular divergence of gypsy sequences between D. virilis and D. subobscura is estimated at 16 MY, whereas the most likely divergence time of these two species is more than 60 MY. These data strongly suggest that gypsy sequences have been horizontally transferred between these species.
Asunto(s)
Elementos Transponibles de ADN , Drosophila melanogaster/genética , Drosophila/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Evolución Biológica , Mapeo Cromosómico , Clonación Molecular , ADN , Datos de Secuencia Molecular , Homología de Secuencia de Aminoácido , Homología de Secuencia de Ácido Nucleico , Especificidad de la Especie , TransfecciónRESUMEN
Eight Drosophila species of the obscura subgroup were screened for sequences homologous to the gypsy retrotransposon of D. melanogaster. Molecular characterization of gypsy sequences was first approached through digesting genomic DNAs from these obscura species with appropriate restriction enzymes and subjecting them to Southern blot analysis. The results of this analysis indicate that gypsy-homologous sequences are well conserved among species of the obscura subgroup. With the exception of D. guanche, all other species bear a 7 kb Xho I fragment that represents the complete element in D. melanogaster. Lower molecular weight fragments that could be deleted elements, are shared by different species. Both types of element probably existed before the divergence of this subgroup. Two different species clusters could be established on the basis of hybridization patterns, one represented by D. subobscura and its relative species D. guanche and D. madeirensis, and the other, in which D. obscura, D. tristis and D. subsilvestris are included.