Many countries in Africa, and more generally those in the Global South with tropical areas, are plagued by illnesses that the wealthier parts of the world (mainly ‘the West’) neither suffer from nor put systematic effort into preventing, treating or curing. What does an ethic with a recognizably African pedigree entail for the ways various agents ought to respond to such neglected diseases? As many readers will know, a characteristically African ethic prescribes weighty duties to aid on the part of those in a position to do so, and it therefore entails that there should have been much more contribution from the Western, ‘developed’ world. However, what else does it prescribe, say, on the part of sub‐Saharan governments and the African Union, and are they in fact doing it? I particularly seek to answer these questions here, by using the 2013‐16 Ebola crisis in West Africa to illustrate what should have happened but what by and large did not. 相似文献
Dynein heavy chains are motor proteins that comprise a large gene family found across eukaryotes. We have investigated this gene family in four ciliate species: Ichthyophthirius, Oxytricha, Paramecium, and Tetrahymena. Ciliates appear to encode more dynein heavy chain genes than most eukaryotes. Phylogenetic comparisons demonstrated that the last common ancestor of the ciliates that were examined expressed at least 14 types of dynein heavy chains with most of the expansion coming from the single‐headed inner arm dyneins. Each of the dyneins most likely performed different functions within the cell. 相似文献
Downy mildew, caused by the oomycete pathogen Peronospora belbahrii, is a devastating foliar disease of basil in the United States and worldwide. Currently there are very few chemistries or organic choices registered to control this disease. In this study, two systemic acquired resistance (SAR) inducers, acibenzolar‐S‐methyl (ASM) and β‐aminobutyric acid (BABA), were evaluated for their in vitro effects on the pathogen, for their potential to control basil downy mildew in greenhouses, and for changes in peroxidase activity in basil plants treated with these two SAR inducers. No significant inhibition of sporangial germination was detected in water agar amended with ASM at concentrations lower than 100 mg/l or with BABA at concentrations lower than 500 mg/l. Efficacy of ASM and BABA in greenhouses varied depending on the rate, method and timing of application. The area under the disease progress curve (AUDPC) of disease severity was significantly reduced compared to the non‐treated control when ASM was sprayed (in all experiments) or drenched (in one out of two experiments) pre‐, or pre‐ + post‐inoculation at rates of 25–400 mg/l. Three weekly post‐inoculation sprays of ASM at the rate of 50 mg/l reduced AUDPC by 93.0 and 47.2% when started 3 and 7 days after inoculation (DAI), respectively. The AUDPC of disease severity was also significantly reduced when BABA was sprayed pre‐ + post‐inoculation at rates of 125–500 mg/l. According to the prediction using a log‐logistic function, 50% maximum disease protection was achieved at a concentration of 27.5 mg/l of ASM. Basil plants treated with these two SAR inducers and challenged with the pathogen showed significantly higher peroxidase activity than the non‐treated control at 8 DAI. Temporally, the highest activity of peroxidase was detected at 8 DAI, decreased at 15 DAI and waned further at 23 DAI. 相似文献
In Arabidopsis, AUXIN RESPONSE FACTOR 3 (ARF3) belongs to the auxin response factor (ARF) family that regulates the expression of auxin‐responsive genes. ARF3 is known to function in leaf polarity specification and gynoecium patterning. In this study, we discovered a previously unknown role for ARF3 in floral meristem (FM) determinacy through the isolation and characterization of a mutant of ARF3 that enhanced the FM determinacy defects of agamous (ag)‐10, a weak ag allele. Central players in FM determinacy include WUSCHEL (WUS), a gene critical for FM maintenance, and AG and APETALA2 (AP2), which regulate FM determinacy by repression and promotion of WUS expression, respectively. We showed that ARF3 confers FM determinacy through repression of WUS expression, and associates with the WUS locus in part in an AG‐dependent manner. We demonstrated that ARF3 is a direct target of AP2 and partially mediates AP2's function in FM determinacy. ARF3 exhibits dynamic and complex expression patterns in floral organ primordia; altering the patterns spatially compromised FM determinacy. This study uncovered a role for ARF3 in FM determinacy and revealed relationships among genes in the genetic network governing FM determinacy. 相似文献
Studies have documented changes in animal body sizes over the last century, but very little is known about changes in plant sizes, even though reduced plant productivity is potentially responsible for declines in size of other organisms. Here, I ask whether warming trends in the Great Basin have affected plant size by measuring specimens preserved on herbarium sheets collected between 1893 and 2011. I asked how maximum and minimum temperatures, precipitation, and the Pacific Decadal Oscillation (PDO) in the year of collection affected plant height, leaf size, and flower number, and asked whether changes in climate resulted in decreasing sizes for seven annual forbs. Species had contrasting responses to climate factors, and would not necessarily be expected to respond in parallel to climatic shifts. There were generally positive relationships between plant size and increased minimum and maximum temperatures, which would have been predicted to lead to small increases in plant sizes over the observation period. While one species increased in size and flower number over the observation period, five of the seven species decreased in plant height, four of these decreased in leaf size, and one species also decreased in flower production. One species showed no change. The mechanisms behind these size changes are unknown, and the limited data available on these species (germination timing, area of occupancy, relative abundance) did not explain why some species shrank while others grew or did not change in size over time. These results show that multiple annual forbs are decreasing in size, but that even within the same functional group, species may have contrasting responses to similar environmental stimuli. Changes in plant size could have cascading effects on other members of these communities, and differential responses to directional change may change the composition of plant communities over time. 相似文献
The neuronal endocannabinoid system is known to depress synaptic inputs retrogradely in an activity‐dependent manner. This mechanism has been generally described for excitatory glutamatergic and inhibitory GABAergic synapses. Here, we report that neurones in the auditory brainstem of the Mongolian gerbil (Meriones unguiculatus) retrogradely regulate the strength of their inputs via the endocannabinoid system. By means of whole‐cell patch‐clamp recordings, we found that retrograde endocannabinoid signalling attenuates both glycinergic and glutamatergic post‐synaptic currents in the same types of neurones. Accordingly, we detected the cannabinoid receptor 1 in excitatory and inhibitory pre‐synapses as well as the endocannabinoid‐synthesising enzymes (diacylglycerol lipase α/β, DAGLα/β) post‐synaptically through immunohistochemical stainings. Our study was performed with animals aged 10–15 days, that is, in the time window around the onset of hearing. Therefore, we suggest that retrograde endocannabinoid signalling has a role in adapting inputs during the functionally important switch from spontaneously generated to sound‐related signals.
Genomic regions associated with coat color and pigmented areas of the head were identified for Fleckvieh (dual‐purpose Simmental), a red‐spotted and white‐headed cattle breed. Coat color was measured with a chromameter, implementing the CIELAB color space and resulting in numerical representation of lightness, color intensity, red/green and blue/yellow color components, rather than subjective classification. Single marker regression analyses with fixed effects of the sex and barn were applied, and significant regions were determined with the local false discovery rate methodology. The PMEL and ERBB3 genes on chromosome 5 were in the most significant region for the color measurements. In addition to the blue/yellow color component and color intensity, the AP3B2 gene on chromosome 21 was identified. Its function was confirmed for similar traits in a range of model species. The KIT gene on chromosome 6 was found to be strongly associated with the inhibition of circum‐ocular pigmentation and pigmented spots on the cheek. 相似文献
We analysed the levels of Alternaria, Cladosporium, Fusarium and Penicillium verrucosum in grain samples harvested in 2011 and 2012 from conventional and organic farms using qPCR. In general, both Alternaria and Cladosporium occurred in all cereal grains in the highest quantities, followed by P. verrucosum and Fusarium. Alternaria, Cladosporium and P. verrucosum had the highest levels in crop mixtures, barley and rye and lower levels in wheat, while Fusarium levels were the highest in crop mixtures and wheat. The levels of Alternaria and P. verrucosum were higher in organic rye and wheat than conventional grains. Although the level of Fusarium was higher in conventional than organic rye, opposite results were obtained for crop mixtures. A positive correlation was found between Alternaria, Cladosporium and P. verrucosum, indicating that similar factors might affect the distribution of these fungi in grains. 相似文献
A study of nematodes associated with the large larch bark beetle Ips cembrae (Heer 1836) was carried out at three locations in the Czech Republic. The proportion of beetles infested by endoparasitic nematodes (representatives of genera Contortylenchus, Parasitylenchus, Cryptaphelenchus and Parasitorhabditis) ranged from 29.9 to 50.9%. Significant differences were determined in nematode infestation levels among locations, generations and sampling methods. No differences were found in infestation rates between males and females. The percentage of bark beetles with phoretic nematodes ranged from 18 to 42.9%. Phoretic nematodes directly found under elytra, on wings and between body segments of the bark beetles belong to the genus Micoletzkya. However, adults and juveniles of other two phoretic species Laimaphelenchus penardi and Bursaphelenchus sp. were found in the gallery frass of I. cembrae. Infestation by phoretic nematodes positively correlated with the presence of mites under elytra. 相似文献
Previous molecular assessments of the red algal order Rhodymeniales have confirmed its monophyly and distinguished the six currently recognized families (viz. Champiaceae, Faucheaceae, Fryeellaceae, Hymenocladiaceae, Lomentariaceae, and Rhodymeniaceae); however, relationships among most of these families have remained unresolved possibly as a result of substitution saturation at deeper phylogenetic nodes. The objective of the current study was to improve rhodymenialean systematics by increasing taxonomic representation and using a more robust multigene dataset of mitochondrial (COB, COI/COI‐5P), nuclear (LSU, EF2) and plastid markers (psbA, rbcL). Additionally, we aimed to prevent phylogenetic inference problems associated with substitution saturation (particularly at the interfamilial nodes) by removing fast‐evolving sites and analyzing a series of progressively more conservative alignments. The Rhodymeniales was resolved as two major lineages: (i) the Fryeellaceae as sister to the Faucheaceae and Lomentariaceae; and (ii) the Rhodymeniaceae allied to the Champiaceae and Hymenocladiaceae. Support at the interfamilial nodes was highest when 20% of variable sites were removed. Inclusion of Binghamiopsis, Chamaebotrys, and Minium, which were absent in previous phylogenetic investigations, established their phylogenetic affinities while assessment of two genera consistently polyphyletic in phylogenetic analyses, Erythrymenia and Lomentaria, resulted in the proposition of the novel genera Perbella and Fushitsunagia. The taxonomic position of Drouetia was reinvestigated with re‐examination of holotype material of D. coalescens to clarify tetrasporangial development in this genus. In addition, we added three novel Australian species to Drouetia as a result of ongoing DNA barcoding assessments—D. aggregata sp. nov., D. scutellata sp. nov., and D. viridescens sp. nov. 相似文献
Coral bleaching and mortality are predicted to increase as climate change‐induced thermal‐stress events become more frequent. Although many studies document coral bleaching and mortality patterns, few studies have examined deviations from the expected positive relationships among thermal stress, coral bleaching, and coral mortality. This study examined the response of >30,000 coral colonies at 80 sites in Palau, during a regional thermal‐stress event in 2010. We sought to determine the spatial and taxonomic nature of bleaching and examine whether any habitats were comparatively resistant to thermal stress. Bleaching was most severe in the northwestern lagoon, in accordance with satellite‐derived maximum temperatures and anomalous temperatures above the long‐term averages. Pocillopora populations suffered the most extensive bleaching and the highest mortality. However, in the bays where temperatures were higher than elsewhere, bleaching and mortality were low. The coral‐community composition, constant exposure to high temperatures, and high vertical attenuation of light caused by naturally high suspended particulate matter buffered the corals in bays from the 2010 regional thermal‐stress event. Yet, nearshore reefs are also most vulnerable to land‐use change. Therefore, nearshore reefs should be given high conservation status because they provide refugia for coral populations as the oceans continue to warm. 相似文献
DNA barcoding aims to develop an efficient tool for species identification based on short and standardized DNA sequences. In this study, the DNA barcode paradigm was tested among the genera of the tribe Sisyrinchieae (Iridoideae). Sisyrinchium, with more than 77% of the species richness in the tribe, is a taxonomically complex genus. A total of 185 samples belonging to 98 species of Sisyrinchium, Olsynium, Orthrosanthus and Solenomelus were tested using matK, trnH‐psbA and internal transcribed spacer (ITS). Candidate DNA barcodes were analysed either as single markers or in combination. Detection of a barcoding gap, similarity‐based methods and tree‐based analyses were used to assess the discrimination efficiency of DNA barcodes. The levels of species identification obtained from plastid barcodes were low and ranged from 17.35% to 20.41% for matK and 5.11% to 7.14% for trnH‐psbA. The ITS provided better results with 30.61–38.78% of species identified. The analyses of the combined data sets did not result in a significant improvement in the discrimination rate. Among the tree‐based methods, the best taxonomic resolution was obtained with Bayesian inference, particularly when the three data sets were combined. The study illustrates the difficulties for DNA barcoding to identify species in evolutionary complex lineages. Plastid markers are not recommended for barcoding Sisyrinchium due to the low discrimination power observed. ITS gave better results and may be used as a starting point for species identification. 相似文献
Phylogenetic relationships in the family Delphinidae have been widely debated. We examined 347 skulls of Tursiops, Stenella, Delphinus, Steno, Lagenodelphis, and Sousa in order to resolve the phylogenetic position of Australian species of Tursiops. Five Tursiops type specimens were included. Cranial morphology was described using 2‐dimensional (2‐D) and 3‐dimensional geometric morphometrics (3‐GM), counts and categorical data. Analyses showed a clear morphological separation of Tursiops, including type specimens, from other genera. The three Stenella species did not cluster together. Stenella attenuata clustered with Delphinus delphis, and Stenella coeruleoalba with Lagenodelphis hosei. Length and width of the skull and rostrum were important discriminators in both methods. For 3‐D data, round vs. angular posterior skull shape distinguished some genera. Taxa that overlapped in the multivariate analyses had different mean tooth counts. Our study challenges genetic studies that identified Tursiops as polyphyletic, with T. aduncus closer to S. attenuata. 相似文献
Pseudoditrichum mirabile, the only species of Pseudoditrichaceae, has been known for a long time from a single collection from the Canadian Arctic. Its systematic position remained enigmatic due to similarity in gametophyte structure with Ditrichaceae, a family that has simple peristomes, whereas the peristome in Pseudoditrichum is double. Due to this difference, Pseudoditrichum was classified in either Funariales or Bryales. A recent discovery of this species in the Anabar Plateau in northern Siberia has allowed its phylogenetic position to be tested based on plastid rps4 and rbcL and mitochondrial nad5 sequences. The results of this research reject the earlier hypotheses. Instead, the molecular analysis resolves Pseudoditrichum in a clade with Chrysoblastella chilensis (formerly Ditrichaceae) in the haplolepideous lineage. The peristome of Pseudoditrichum is of a previously unknown type with a fully developed exostome and hyaline endostome elements opposite the exostome teeth, based not on the 4:2:4 peristomial formula, but on 4:2:3. Double peristomes of the same type, albeit rather strongly reduced, occur in Catoscopium, Chrysoblastella, Distichium and Ditrichum flexicaule. The polyphyly of Ditrichaceae is confirmed by molecular phylogenetic analysis, and Ditrichum flexicaule and D. gracile are segregated into the new genus Flexitrichum and family Flexitrichaceae. An independent status of the recently resurrected family Distichiaceae is supported, and segregation of Chrysoblastella and Saelania into new monospecific families is proposed. 相似文献