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71.
N6‐methyladenine is the most widespread mRNA modification. A subset of human box C/D snoRNA species have target GAC sequences that lead to formation of N6‐methyladenine at a key trans Hoogsteen‐sugar A·G base pair, of which half are methylated in vivo. The GAC target is conserved only in those that are methylated. Methylation prevents binding of the 15.5‐kDa protein and the induced folding of the RNA. Thus, the assembly of the box C/D snoRNP could in principle be regulated by RNA methylation at its critical first stage. Crystallography reveals that N6‐methylation of adenine prevents the formation of trans Hoogsteen‐sugar A·G base pairs, explaining why the box C/D RNA cannot adopt its kinked conformation. More generally, our data indicate that sheared A·G base pairs (but not Watson–Crick base pairs) are more susceptible to disruption by N6mA methylation and are therefore possible regulatory sites. The human signal recognition particle RNA and many related Alu retrotransposon RNA species are also methylated at N6 of an adenine that forms a sheared base pair with guanine and mediates a key tertiary interaction. 相似文献
72.
MJ Müller MP Mendon?a IR Oliveira LPL de Oliveira VLS Valente VH Valiati 《Neotropical Entomology》2012,41(2):112-120
We describe for the first time the sexual behavior and the courtship song of males of the African fly Zaprionus indianus (Gupta), a recent invader of South America. The male courtship song is formed by monocyclic pulses and the courtship behavior is simple when compared to that of species of Drosophila. Two interpulse interval (IPI) distributions were observed: pre-mounting and mounting. No significant difference was observed between the pre-mounting IPIs of males that descended from three geographical populations from South America. We also observed the songs produced by females and the homosexual behavior exhibited by males. A sequence of bursts is produced by females as a refusal signal against males, while males emit a characteristic song that identifies sex genus, which differs from the courtship song. The short courtship and mating latencies recorded reveal vigorous males and receptive females, respectively. 相似文献
73.
Alomá Moreno O y MJ Freuler 《Phyton》2015,84(2):466-472
The present study of the Orchidaceae family was carried out in Guamuahaya’s mountain range, from 2000 to March 2013. Fifteen districts were explored after 33 expeditions in the Province of Cienfuegos. Ninety two plant species were identified in the studied area, taking into account the ecological parameters of the mountainous areas of Cienfuegos and Cumanayagua municipalities. 相似文献
74.
75.
Susan C Burleigh Teun van de Laar Corné JM Stroop Wout MJ van Grunsven Niaobh O’Donoghue Pauline M Rudd Gavin P Davey 《BMC biotechnology》2011,11(1):1-17
Background
The photorespiratory nitrogen cycle in C3 plants involves an extensive diversion of carbon and nitrogen away from the direct pathways of assimilation. The liberated ammonia is re-assimilated, but up to 25% of the carbon may be released into the atmosphere as CO2. Because of the loss of CO2 and high energy costs, there has been considerable interest in attempts to decrease the flux through the cycle in C3 plants. Transgenic tobacco plants were generated that contained the genes gcl and hyi from E. coli encoding glyoxylate carboligase (EC 4.1.1.47) and hydroxypyruvate isomerase (EC 5.3.1.22) respectively, targeted to the peroxisomes. It was presumed that the two enzymes could work together and compete with the aminotransferases that convert glyoxylate to glycine, thus avoiding ammonia production in the photorespiratory nitrogen cycle.Results
When grown in ambient air, but not in elevated CO2, the transgenic tobacco lines had a distinctive phenotype of necrotic lesions on the leaves. Three of the six lines chosen for a detailed study contained single copies of the gcl gene, two contained single copies of both the gcl and hyi genes and one line contained multiple copies of both gcl and hyi genes. The gcl protein was detected in the five transgenic lines containing single copies of the gcl gene but hyi protein was not detected in any of the transgenic lines. The content of soluble amino acids including glycine and serine, was generally increased in the transgenic lines growing in air, when compared to the wild type. The content of soluble sugars, glucose, fructose and sucrose in the shoot was decreased in transgenic lines growing in air, consistent with decreased carbon assimilation.Conclusions
Tobacco plants have been generated that produce bacterial glyoxylate carboligase but not hydroxypyruvate isomerase. The transgenic plants exhibit a stress response when exposed to air, suggesting that some glyoxylate is diverted away from conversion to glycine in a deleterious short-circuit of the photorespiratory nitrogen cycle. This diversion in metabolism gave rise to increased concentrations of amino acids, in particular glutamine and asparagine in the leaves and a decrease of soluble sugars. 相似文献76.
The suitability of using macroinvertebrates as bioindicators of stream water quality was tested in the Mkondoa River in an agricultural area at Kilosa, using the rapid bioassessment protocol. The family biotic index (FBI) showed marked variation in water quality along the stream from values ranging from 4.1 to 5.0 in the upstream reaches, indicating good water quality, 5.3 to 5.5 in the mid-reaches and 6.0 to 6.5 in the lower reaches. The water quality index (WQI) indicated that water quality was fair (77 ± 0.98) in the upstream reach of the Mkondoa, marginal (55 ± 0.86) in the midstream reach and poor (33 ± 0.45) in the downstream reach. There were significant relationships between biological oxygen demand and dissolved oxygen and the occurrence of specific taxa, mainly Chironomus and Caenis. Significant changes in macroinvertebrate abundance were mostly related to changes in water quality. As in other parts of the world, macroinvertebrate communities proved to be good biological indicators of water quality and they should be used as bioindicators in long-term monitoring of this river. 相似文献
77.
78.
George F. Estabrook David W. Burk Dennis R. Inman Peter B. Kaufman James R. Wells John D. Jones Najati Ghosheh 《American journal of botany》1985,72(2):209-216
The concentrations of 15 heavy metals in aquatic plants on Charity Island was compared to those in plants on the shoreline of Saginaw Bay, Lake Huron, U.S.A. Heavy metal concentrations were measured by neutron activation analysis. Charity Island was found to have significantly higher levels of nine of fifteen metals investigated. This indicates that distance from known pollution source was not the only factor affecting the heavy metal accumulation of the aquatic plants. 相似文献
79.
Stoats are significant predators of native fauna in New Zealand. They occur in many habitat types and consume a wide range of prey. The diet of stoats in the Tasman River, South Canterbury, was studied by analysis of scats and den contents. Analysis of 206 scats showed that stoats ate mainly lagomorphs, birds and invertebrates. Minor components included mice, lizards, fish and hedgehogs. Stoats ate more birds in spring than in autumn, and female stoats ate more invertebrates than did males. The contents of 219 dens collected in the same area at the same time provided further information. Birds and lagomorphs occurred at high frequency in dens, and other components were minor. Remains in dens were larger than in scats and allowed identification of many more prey items to species level. Den contents revealed a potentially substantial impact of stoats on threatened shorebirds locally; this impact was not detected by analysis of scats. 相似文献
80.
Lucia F. C. Pedrosa Amy K. Motley Teri D. Stevenson Kristina E. Hill Raymond F. Burk 《Biological trace element research》2012,149(3):377-381
Whole-body selenium is regulated by excretion of the element. Reports of studies carried out using isotopic tracers have led to the conclusion that urinary selenium excretion is regulated by selenium intake but that fecal excretion is not. Because of the limitations of tracer studies, we measured urinary and fecal selenium excretion by mice with selenium intakes in the form of sodium selenite ranging from deficient to almost toxic. Tissue and whole-body selenium concentrations increased sharply between deficient and adequate selenium intakes, reflecting tissue accumulation of selenium in the form of selenoproteins. Once the requirement for selenium had been satisfied, a 31-fold further increase in intake resulted in less than doubling of tissue and whole-body selenium, demonstrating the effectiveness of selenium excretion by the mouse. Urinary selenium excretion increased with increases in dietary selenium intake. Fecal selenium excretion, which was 20 to 30?% of the selenium excreted in the physiological range, responded to moderately high selenium intake but did not increase further when selenium intake was increased to even higher levels. Thus, fecal selenium excretion contributes to regulation of whole-body selenium at physiological selenium intakes. The pattern of its response to the full spectrum of selenium intakes was different from the urinary excretion response, suggesting that the mechanisms of fecal and urinary routes of excretion are different. 相似文献