RESUMEN
Using Drosophila melanogaster, we examined changes in the activities of some of the respiratory enzyme complexes with age. The age-related decreases of enzyme activities were observed especially in complex I. We also examined changes in the ultrastructure of mitochondria in the flight muscles of thoraces. The results indicated that the mitochondrial size varied more widely in aged flies than in young ones, in addition to the slight increase in the average size with age. These changes had already appeared before the survival began to decrease, clearly indicating that the accumulation of such changes seriously damages mitochondrial function.
Asunto(s)
Drosophila melanogaster/enzimología , Drosophila melanogaster/fisiología , Proteínas del Complejo de Cadena de Transporte de Electrón/metabolismo , Mitocondrias/enzimología , Mitocondrias/ultraestructura , Factores de Edad , Animales , Femenino , Humanos , Masculino , Músculos/ultraestructuraRESUMEN
Mitochondrial DNA (mtDNA) is generally packaged into the mitochondrial nucleoid (mt-nucleoid) by a high-mobility group (HMG) protein. Glom is an mtDNA-packaging HMG protein in Physarum polycephalum. Here we identified a new mtDNA-packaging protein, Glom2, which had a region homologous with yeast Mgm101. Glom2 could bind to an entire mtDNA and worked synergistically with Glom for condensation of mtDNA in vitro. Down-regulation of Glom2 enhanced the alteration of mt-nucleoid morphology and the loss of mtDNA induced by down-regulation of Glom, and impaired mRNA accumulation of some mtDNA-encoded genes. These data suggest that Glom2 may organize the mt-nucleoid coordinately with Glom.
Asunto(s)
Empaquetamiento del ADN , ADN Mitocondrial/metabolismo , Proteínas de Unión al ADN/metabolismo , Proteínas del Grupo de Alta Movilidad/metabolismo , Physarum polycephalum/genética , Secuencia de Aminoácidos , Clonación Molecular , ADN Mitocondrial/genética , Regulación hacia Abajo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Genes Fúngicos , Proteínas Mitocondriales/genética , Proteínas Mitocondriales/metabolismo , Datos de Secuencia Molecular , Filogenia , Physarum polycephalum/metabolismo , ARN Mensajero/metabolismo , Proteínas de Unión al ARN/metabolismo , Alineación de SecuenciaRESUMEN
The nuclear genome of the human malaria parasite Plasmodium falciparum encodes a homolog of the bacterial HU protein (PfHU). In this study, we characterised PfHU's physiological function. PfHU, which is targeted exclusively to the parasite's plastid, bound its natural target--the plastid DNA--sequence-independently and complemented lack of HU in Escherichia coli. The HU gene could not be knocked-out from the genome of Plasmodium berghei, implying that HU is important for the parasite's survival. As the human cell lacks the HU homolog, PfHU is a potential target for drugs to control malaria.
Asunto(s)
ADN Protozoario/metabolismo , Plasmodium falciparum/fisiología , Plastidios/metabolismo , Proteínas Protozoarias/fisiología , Animales , Secuencia de Bases , Cartilla de ADN , ADN Protozoario/genética , Técnicas de Inactivación de Genes , Prueba de Complementación Genética , Plasmodium falciparum/metabolismo , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismoRESUMEN
For more than 140 years, pollen tube guidance in flowering plants has been thought to be mediated by chemoattractants derived from target ovules. However, there has been no convincing evidence of any particular molecule being the true attractant that actually controls the navigation of pollen tubes towards ovules. Emerging data indicate that two synergid cells on the side of the egg cell emit a diffusible, species-specific signal to attract the pollen tube at the last step of pollen tube guidance. Here we report that secreted, cysteine-rich polypeptides (CRPs) in a subgroup of defensin-like proteins are attractants derived from the synergid cells. We isolated synergid cells of Torenia fournieri, a unique plant with a protruding embryo sac, to identify transcripts encoding secreted proteins as candidate molecules for the chemoattractant(s). We found two CRPs, abundantly and predominantly expressed in the synergid cell, which are secreted to the surface of the egg apparatus. Moreover, they showed activity in vitro to attract competent pollen tubes of their own species and were named as LUREs. Injection of morpholino antisense oligomers against the LUREs impaired pollen tube attraction, supporting the finding that LUREs are the attractants derived from the synergid cells of T. fournieri.
Asunto(s)
Factores Quimiotácticos/metabolismo , Defensinas/metabolismo , Magnoliopsida/citología , Magnoliopsida/crecimiento & desarrollo , Tubo Polínico/crecimiento & desarrollo , Secuencia de Aminoácidos , Factores Quimiotácticos/química , Factores Quimiotácticos/farmacología , Defensinas/química , Defensinas/farmacología , Etiquetas de Secuencia Expresada , Magnoliopsida/efectos de los fármacos , Magnoliopsida/genética , Datos de Secuencia Molecular , Oligonucleótidos Antisentido/genética , Tubo Polínico/efectos de los fármacos , Tubo Polínico/genética , ARN de Planta/antagonistas & inhibidores , ARN de Planta/genética , ARN de Planta/metabolismo , Transcripción GenéticaRESUMEN
We determined the complete nucleotide sequence of the A+T-rich region of the maII type of mtDNA in D. mauritiana. The nucleotide sequence was found to contain 3,206 bp. Three types of conserved element, i.e., type I element, type II element, and T-stretch, were included in this sequence, as reported for D. melanogaster. Comparison between the two species revealed that the type I elements were less conserved than the type II elements. However, each of these type I elements contained a G-stretch within a loop of a putative stem-loop-forming sequence, which has also been observed in D. melanogaster. Moreover, in both type I and type II repeat arrays, the elements closest to the T-stretch diverged the most, due to nucleotide substitution and/or the insertion of short repeats. Sequence comparison of the two complete sequences of the A+T-rich region of D. melanogaster and the maII type of D. mauritiana, as well as comparison of partial sequences in other types of mtDNA within the melanogaster complex, suggested that the A+T-rich region in this complex has been maintained by concerted evolution after the duplication of two types of element, i.e., type I and type II.
Asunto(s)
Secuencia Rica en At , ADN Mitocondrial , Drosophila/genética , Mitocondrias/genética , Secuencias Repetitivas de Ácidos Nucleicos , Animales , Secuencia de Bases , Femenino , Datos de Secuencia MolecularRESUMEN
Cumulative damage due to reactive oxygen species (ROS) in mitochondria, especially in mitochondrial DNA (mtDNA), would result in a decrease in mitochondrial respiratory function and contributes to the age-related decline in the physiological functioning of organisms. Previously, we reported the tissue-specific accumulation of deleted mtDNA with age in Drosophila melanogaster. In the present study, to understand the mechanism by which mtDNA deletion is generated with age, nucleotide sequences of deleted mtDNA were determined. Consequently, 33 different sequences each containing a deletion were obtained from flies that were more than 55-day-old. Most of the deletions were found to be flanked by short direct repeats. The present results, together with those from other animals, suggest that there is a common mechanism generating mtDNA deletions through direct repeats.
Asunto(s)
Envejecimiento/genética , ADN Mitocondrial/genética , Drosophila melanogaster/genética , Secuencias Repetitivas de Ácidos Nucleicos , Eliminación de Secuencia , Animales , Secuencia de Bases , Femenino , Masculino , Mitocondrias/genética , Datos de Secuencia MolecularRESUMEN
Cumulative damage in mitochondria by reactive oxygen species is thought to result in a decrease in mitochondrial respiratory function and to contribute to the age-related decline in the physiological function of organisms. The mitochondrial genome is also subjected to damage with age through deletions. The accumulation of deleted mitochondrial DNA (mtDNA) has been observed in various animals, but still remains unclear in insects. We examined the accumulation of deleted mtDNA in D. melanogaster at various ages from larvae to 65-day-old adults. When DNA extracted from whole bodies was examined by PCR and Southern hybridization, the age-related accumulation of deletions was not clear. However, when the accumulation of deleted mtDNA with age was examined separately in three parts of the body (head, thorax and abdomen), deleted mtDNA signals were detected more frequently in the thorax and the accumulation was age-dependent. Three of the deleted mtDNA were cloned, and the breakpoints of the deletions were identified. These results strongly suggest that deleted mtDNA accumulates in Drosophila with age in a tissue-specific manner.