The nucleotide sequence of the 5' ends of the 28S-like rRNA molecules of five species of helminths was determined directly, using a variation on the dideoxynucleotide chain-termination method which ...requires only 10 micrograms of total cellular RNA for analysis. Nucleotide sequence comparisons over 208 bases allowed the phylogeny of these organisms to be determined. The data show that the rRNA sequence of Nematospiroides dubius, a nematode, is as divergent from that of two platyhelminths, Hymenolepis diminuta and Schistosoma mansoni, as it is from the rRNA sequence of the two nematodes Onchocerca gibsoni and Brugia pahangi. The latter two appear to be very closely related, whereas the two platyhelminths are more distant from each other. The study demonstrates the usefulness and generality of rRNA sequencing for the systematic phylogenetic classification of parasitic organisms whose tissues are only available in relatively small amounts.
A U3 RNA variant has been identified in mouse, the abundance of which relative to the previously characterized major form (U3B) appears to vary to a large extent depending upon the cell origin. Its ...partial sequence analysis shows that it is clearly related to the U3A form previously described in rat. Sequence comparisons suggest that the separation of the two forms of U3 genes now found in rat and mouse represent a relatively ancient event in rodent evolution. While mouse U3B RNA is encoded by four clustered genes, the U3A variant is encoded by a unique gene. Both mouse U3 RNAs differ substantially in primary structure (more than 10% divergence). Although rodent U3 RNAs exhibit a largely similar secondary structure, a specific difference between the A and B form can nevertheless be observed.
The adenosine analog 5,6 dichloro-1-beta-ribofuranosyl benzimidazole (DRB) inhibits specifically mRNA production in eukaryotic cells, with concomitant alterations in pre-rRNA processing and nucleolar ...ultrastructure. We have focused our analysis on the effects of drug treatment on rRNA transcription through observations of spread ribosomal RNA (rRNA) transcription units from hamster cells. A significant increase in the size of ribosomal matrix units is paralleled by the appearance of abnormally large RNP structures containing elongating pre-rRNA. These structures correspond to nucleolar perichromatin granules which are known to appear in various conditions of cell growth when rRNA processing is altered. It is proposed that DRB-induced impairments in rRNA maturation are largely determined by alterations in the rRNA transcription process.
Due to their high information content and their particular mode of variation, large rRNA molecules potentially represent powerful indicators of phylogenetic relationships. Even partial sequences may ...suffice to generate reliable estimations, provided they correspond to well-chosen portions of the molecule. We have systematically analyzed a specific portion of the large rRNA (the region extending over nearly 400 nucleotides from the 5' end) as a general index of eucaryotic phylogeny. By means of fast and direct rRNA sequencing, we have determined the sequence of this region for 20 additional eucaryotes, including several representatives of each vertebrate class, an invertebrate metazoan (mussel), a fungus (Schizosaccharomyces pombe), and three higher plants. Comparative treatment of these new data and previously reported rRNA sequences shows that this region can serve as an indicator of eucaryotic phylogeny for evaluating both long-range and short-range relationships. Its conservative domains appear to possess a rather uniform rate of nucleotide changes in all the eucaryotic lineages analyzed and the phylogenetic tree we derived agrees with classical views.
In this study, the effects of cadmium (Cd) on lipid peroxidation, electrolyte leakage, protein oxidation, ascorbate peroxidase (APX; E.C. 1.11.1.11), catalase (CAT; E.C. 1.11.1.6) and superoxide ...dismutase (SOD; E.C. 1.15.1.1) activities, and ascorbic acid, non-protein thiol groups and total soluble protein contents in cucumber seedlings (Cucumis sativus L.) were investigated. Seedlings were grown in vitro in an agar-solidified substrate containing four Cd levels as CdCl2 (0, 100, 400, and 1000 µmol L-1) for 10 d. The lowest Cd level decreased the malondialdehyde concentration. Electrolyte leakage increased only at 1000 µmol Cd L-1, whereas protein oxidation and total soluble protein content were enhanced at 400 and 1000 µmol Cd L-1. Activity of APX was inhibited while the activities of CAT and SOD were increased at all Cd concentrations. Ascorbic acid was enhanced at 400 and 1000 µmol Cd L-1 whereas non-protein thiol groups were increased at all Cd supplies. The results evidence the importance of the enzymatic and non-enzymatic antioxidant system in response to cadmium toxicity in cucumber seedlings.
No presente estudo, os efeitos do cádmio (Cd) sobre a peroxidação lipídica, o extravazamento de eletrólitos, a oxidação protéica, a atividade das enzimas peroxidase do ascorbato (APX; E.C. 1.11.1.11), catalase (CAT; E.C. 1.11.1.6) e dismutase do superóxido (SOD; E.C. 1.15.1.1) e as concentrações de ácido ascórbico, de grupos tióis não-protéicos e de proteínas solúveis totais foram investigados em plântulas de pepino (Cucumis sativus L.). As plântulas foram cultivadas in vitro em um substrato solidificado com ágar contendo quatro concentrações de Cd na forma de CdCl2 (0, 100, 400 e 1000 µmol L-1), durante 10 d. A menor concentração de Cd diminuiu a concentração de aldeído malônico. O extravazamento de eletrólitos aumentou somente em 1000 µmol Cd L-1, enquanto a oxidação protéica e a concentração de proteínas solúveis totais foram aumentadas somente em 400 e 1000 µmol Cd L-1. A atividade da APX foi inibida, enquanto as atividades da CAT e SOD foram aumentadas em todas as concentrações de Cd. A concentração de ácido ascórbico aumentou sob 400 e 1000 µmol Cd L-1, enquanto a de grupos tióis não-protéicos aumentou em todas as concentrações de Cd. Os resultados evidenciam a importância do sistema antioxidante enzimático e não-enzimático na resposta à toxicidade de cádmio em plântulas de pepino.
Aluminum toxicity is a serious problem in Brazilian soils and selecting potato clones is an important strategy to produce this crop on these kinds of soils. Potato clones, Macaca, SMIC148-A, Dakota ...Rose, and Solanum microdontum, were grown in a nutrient solution (pH 4.0) with 0, 50, 100, 150 and 200 mg Al L-1. After 7 d, Al concentration in both root system and shoot of all clones increased linearly with increasing Al levels. Based on relative root growth, S. microdontum and SMIC148-A were considered Al-tolerant clones, whereas Macaca and Dakota Rose were considered Al-sensitive. Shoot growth in Macaca linearly decreased with increasing Al levels. Root H2O2 concentration in both Al-sensitive clones increased with increasing Al supply, whereas in Al-tolerant clones it either decreased (SMIC148-A) or demonstrated no alteration (S. microdontum). Shoot H2O2 concentration increased linearly in Macaca, whereas for Dakota Rose it showed a quadratic relationship with Al levels. On the other hand, shoot H2O2 concentration in the Al-tolerant clones either demonstrated no alteration (S. microdontum) or presented lower levels (SMIC148-A). Root catalase (CAT) activity in both Al-sensitive clones increased with increasing Al levels, whereas in Al-tolerant clones it either demonstrated no alteration (SMIC148-A) or presented lower levels (S. microdontum). Shoot CAT activity in the S. microdontum increased curvilinearly with increasing Al levels. In all potato clones, chlorophyll concentration showed a curvilinear response to Al supply, where in Al-sensitive clones it decreased upon addition of Al exceeding 100 mg L-1, but in SMIC148-A it increased at levels between approximately 100 and 150 mg L-1, and decreased in S. microdontum regardless of the Al level. Carotenoid concentrations in the Al-sensitive clones were linearly decreased with increasing Al levels. Aluminum supply caused root lipid peroxidation only in the Al-sensitive clones, whereas in the shoot it increased linearly in the Al-sensitive clones and in S. microdontum it only increased at around 50 mg L-1. Most of root protein oxidation was only observed in the Al-sensitive clones. However, shoot protein oxidation was increased with increasing Al levels for all potato clones. These results indicate that oxidative stress caused by Al in potato may harm several components of the cell, mainly in Al-sensitive clones.
Atoxicidade do alumínio é um problema sério em solos brasileiros e a seleção de clones de batata é uma estratégia importante para produzir essa cultura em tais solos. Clones de batata, Macaca, SMIC148-A, Dakota Rose e Solanum microdontum, foram cultivados em solução nutritiva (pH 4.0) com 0, 50, 100, 150 e 200 mg Al L-1. Após 7 d, o teor de Al em raízes e parte aérea em todos clones aumentou linearmente com o suprimento de Al. Baseado no crescimento relativo da raiz, os clones S. microdontum e SMIC148-A foram considerados tolerantes ao Al, enquanto os clones Macaca e Dakota Rose foram considerados sensíveis. O crescimento da parte aérea do clone Macaca diminuiu linearmente com o Al. A concentração de H2O2 nas raízes de ambos os clones sensíveis ao Al aumentou com o suprimento de Al, enquanto nos clones tolerantes houve decréscimo (SMIC148-A) ou falta de resposta (S. microdontum). A concentração de H2O2 na parte aérea aumentou linearmente em Macaca, enquanto em Dakota Rose houve uma relação quadrática com os níveis de Al. Por outro lado, nos clones tolerantes ao Al a concentração de H2O2 não foi alterada (S. microdontum) ou foi reduzida (SMIC148-A). A atividade da catalase (CAT) nas raízes de ambos clones sensíveis ao Al aumentou com o suprimento de Al, enquanto nos clones tolerantes não houve alteração (SMIC148-A) ou, então, redução (S. microdontum). Na parte aérea, a atividade da CAT em S. microdontum aumentou com o suprimento de Al. Em todos clones de batata, a concentração de clorofila variou curvilinearmente em relação ao suprimento de Al; nos clones sensíveis, a concentração de clorofila diminuiu pela adição de Al em níveis acima de 100 mg L-1, porém em SMIC148-A houve aumento na presença de Al (na faixa próxima a 100 e 150 mg L-1) e diminuição em S. microdontum, independentemente do tratamento de Al. A concentração de carotenóides nos clones sensíveis ao Al diminuiu linearmente, em resposta ao Al. O Al aumentou a peroxidação lipídica em raízes dos clones sensíveis, enquanto na parte aérea houve aumento linear nesses clones e também em S. microdontum (próximo a 50 mg Al L-1). A oxidação protéica foi observada principalmente nas raízes dos clones sensíveis ao alumínio. Entretanto, foi observada oxidação protéica na parte aérea de todos clones de batata, em resposta ao Al. Estes resultados indicam que o estresse oxidativo causado por Al em batata pode prejudicar vários componentes celulares, principalmente nos clones sensíveis ao metal.
The structure of the 5' domain of yeast 18S rRNA has been probed by dimethyl sulfate (DMS), either in "native" deproteinized molecules or in the 40S ribosomal subunits. DMS-reacted RNA has been used ...as a template for reverse transcription and a large number of reactive sites, corresponding to all types of bases have been mapped by a primer extension procedure, taking advantage of blocks in cDNA elongation immediately upstream from bases methylated at atom positions involved in the base-pair recognition of the template. Since the same atom positions are protected from DMS in base-paired nucleotides, the secondary structure status of each nucleotide can be directly assessed in this procedure, thus allowing to evaluate the potential contribution of proteins in modulating subunit rRNA conformation. While the DMS probing of deproteinized rRNA confirms a number of helical stems predicted by phylogenetic comparisons, it is remarkable that a few additional base-pairings, while proven by the comparative analysis, appear to require the presence of the bound ribosomal subunit proteins to be stabilized.
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