大豆和百脉根古老原核基因的全基因组鉴定与比较分析

在漫长的进化过程中,高等真核生物从原核生物中获取了大量基因,对这些基因进行鉴定分析,可为研究高等植物系统演化及基因组水平比较分析提供理论依据。为了进一步解析大豆和百脉根古老原核基因在其基因组中所起的作用及进化关系,本研究利用生物信息学技术对大豆和百脉根基因组古老原核基因进行全基因组鉴定,并对其特征及功能进行了比较分析。研究结果表明,大豆(40.6%)古老原核基因的占比高于百脉根(33.9%),且多分布于内共生细胞器线粒体、叶绿体中。此外,古老原核蛋白质的结构域在大豆和百脉根基因组中的分布相似,表明其在大豆和百脉根进化过程中具有较高的共线性和保守性。通过GO注释发现大豆与百脉根中古老原核蛋白主要分布在膜系统、细胞、细胞组分中。在分子功能上,大豆古老原核蛋白更多地参与代谢和发育过程,这可能与其接受了更多的人为选育有关。在生物过程中,古老原核蛋白更多参与催化反应和结合反应,主要以酶的形式在发挥作用。通过比较分析,本研究揭示了古老原核蛋白在大豆和百脉根中进化的独特模式,可为其他豆科植物基因组分析提供一定理论基础。     

La Sota vaccination may not protect against virus shedding and the lesions of velogenic Newcastle disease in commercial turkeys

The aim of this project is to study the clinical signs and lesion of velogenic Newcastle disease (vND) in commercial turkeys, and also to find out if La Sota vaccination offered protection against these signs and lesions. The cockerels were included as positive controls. One hundred and twenty turkey poults and cockerels were divided into eight groups as follows: unvaccinated unchallenged turkeys (UUT), unvaccinated challenged turkeys (UCT), vaccinated unchallenged turkeys (VUT), vaccinated challenged turkeys (VCT), and along the same lines, the cockerel groups were UUC, UCC, VUC and vaccinated challenged cockerels (VCC). Vaccination was at 3 weeks of age while challenge was at 6 weeks of age. The unvaccinated turkeys and cockerels (UCT and UCC) showed different degrees of depression, diarrhoea and later paralysis at challenge. Total mortality was 100% in cockerels within 6 days, but 60% in turkeys. Similar but milder clinical signs were found in the VCC with a total mortality of 13.3%. The VCT showed mild drop in feed and water consumption, and no mortality. All the challenged groups had significant (p < 0.05) loss of weight when compared with their controls. Necropsy showed that while the UCC had severe proventricular haemorrhages, intestinal and caecal tonsil ulcers, the UCT had no digestive tract lesion. There was severe atrophy of the lymphoid organs in all the challenged groups. Histopathological sections of the bursa, spleen and thymus in all the challenged groups with special emphasis on the vaccinated and unvaccinated turkeys with mortalities of 0 and 60%, respectively, had very severe necrosis and depletion of the lymphoid tissue. Virus was isolated from the cloacal swabs. The haemagglutination inhibition antibodies were significantly higher (p < 0.05) in the challenged groups than the unchallenged. The above observations in the intestinal tracts of UCT are of diagnostic significance while the gross and microscopic lesions in the UCT and VCT show that La Sota vaccination may not protect turkeys against the destruction of the lymphoid organs by vND as earlier reported in chickens. This may lead to immunosuppression and production problems in areas where vND is enzootic.     

Effect of CD4+CD25+ T cell-depletion on acute lethal infection of mice with Trypanosoma congolense

Despite the immense socio-economic repercussions of African trypanosomosis (AT), there is currently no effective control measure against the disease. Characterization of mechanisms governing resistance and/or susceptibility to AT could suggest interventions that might lead to more effective disease control. The present study was designed in an attempt to address the possible role of CD4+CD25+ T cells during an acute lethal infection of mice with Trypanosoma congolense, the causative agent of AT in domestic animals, through selective depletion using anti-CD25 monoclonal antibody. Accordingly, CD4+CD25+ T-cell-depletion resulted in a significant reduction or delay in parasitemia, pathology, and mortality, as compared to controls. The apparent resistance in CD4+CD25+-T-cell-depleted mice correlated with a profound suppression of Th2 cytokines in vitro and in vivo, culminating in a net Th1 cytokine environment. Cumulatively, these findings suggest that CD4+CD25+ T-cell- depletion improves the trypanotolerance of highly susceptible BALB/c mice acutely infected with the lethal T. congolense.     

Biomolecular relationships among isolates of<Emphasis Type="Italic">Tomato Yellow Leaf Curl Tanzania Virus</Emphasis>

An investigation of the biological properties of the virus causing tomato yellow leaf curl disease in Tanzania was initiated to compare it with other known tomato yellow leaf curl viruses. Properties relating to acquisition and inoculation feeding time, persistence, mechanical inoculation, seed transmission and host range were studied. Results obtained indicate that the virus was transmitted persistently byBemisia tabaci Genn., but it was not mechanically, sap- or seed-transmissible. Minimum acquisition and inoculation feeding time was 30 min.Capsicum annuum, Datura stramonium, Nicotiana glutinosa, N. tabacum andLycopersicon esculentum were found to be hosts of the virus among the plant species tested, whereasPhaseolus vulgaris was not. It is concluded that the properties of the agent causing yellow leaf curl symptoms in tomato plants from different regions in Tanzania are similar to those ofTomato yellow leaf curl Sardinia virus species studied elsewhere. http://www.phytoparasitica.org posting Feb. 20, 2003.     

Age, genotype and sex effects on growth performance of local chickens kept under improved management in Ghana

Characterisation of animal genetic resources has been recognised globally as an important step towards their sustainable use. Body weight data of local chickens (213 forest and 160 savannah chickens) and 183 French free-ranging SASSO T44 chickens kept under improved management were collected from hatch to 40 weeks of age and analysed to determine the effects of age, genotype and sex on their growth performance. At all ages, SASSO T44 chickens had significantly (P < 0.05) higher weights (2.6–3.2 kg at 28 weeks) than the local chickens (1.2–1.7 kg at 28 weeks). The rate of growth at the earlier ages in the local genotypes (5.57–7.80 g/day) was lower than the range of 13.81–15.42 in SASSO T44 chickens. Except at hatch, savannah chickens were significantly heavier (P < 0.05) than the forest chickens at all ages. Male chickens had significantly (P < 0.05) superior growth rates than females across all genotypes except from the 20th to the 28th week. Growth trends in both sexes depicted linear increase in body weights; however, the rate of increase in body weights was higher in males as compared to females, thus showing clear sexual dimorphism. There were no significant (P > 0.05) differences in the growth rates of SASSO T44 chickens and local genotypes at the later ages (20–28 weeks). Local chickens from the savannah zone had better growth rate than forest chickens. The significant effect of ecozone on the growth potential of local chickens is an indication that their productive potential could be improved through interventions in the environment such as provision of feed and some veterinary care.     

Conservation implications of deforestation across an elevational gradient in the Eastern Arc Mountains, Tanzania

Deforestation is a major threat to the conservation of biodiversity, especially within global centers of endemism for plants and animals. Elevation, the major environmental gradient in mountain regions of the world, produces a rapid turnover of species, where some species may exist only in narrow elevational ranges. We use newly compiled datasets to assess the conservation impact of deforestation on threatened trees across an elevational gradient within the Eastern Arc Mountains of Tanzania. The Eastern Arc has suffered an estimated 80% total loss in historical forest area and has lost 25% of forest area since 1955. Forest loss has not been even across all elevations. The upper montane zone (>1800 m) has lost 52% of its paleoecological forest area, 6% since 1955. Conversely, the submontane habitat (800–1200 m) has lost close to 93% of its paleoecological extent, 57% since 1955. A list of 123 narrowly endemic Tanzanian Eastern Arc tree taxa with defined and restricted elevational ranges was compiled and analyzed in regard to mountain block locations, elevational range, and area of forest within each 100 m elevational band. Half of these taxa have lost more than 90% of paleoecological forest habitat in their elevational range. When elevational range is considered, 98 (80%) of these endemic forest trees should have their level of extinction threat elevated on the IUCN Red List. Conservation efforts in montane hotspots need to consider the extent of habitat changes both within and across elevations and target conservation and restoration efforts throughout these ecosystems’ entire elevational ranges.     

Twenty-eight new microsatellite loci in chicken and their cross-species amplification in Japanese quail and helmeted guinea fowl

Twenty‐eight original chicken microsatellite markers were isolated and characterized to determine their utility as cross‐reactive markers for comparative genetic mapping in the order Galliformes. Primer pairs were typed in 12 unrelated chickens and also tested on Japanese quail and helmeted guinea fowl deoxyribonucleic acid (DNA). Polymorphism was observed in 23 (82.1%) of the markers and the average number of alleles per locus was 2.9 while the mean heterozygosity was 0.19. Eleven (39.3%) of the chicken markers cross‐reacted with Japanese quail DNA and 2 (7.1%) with helmeted guinea fowl DNA. The cross‐reactive markers described would serve as useful resources for comparative genetic mapping in poultry species belonging to the order Galliformes.