Control of rabies: epidemiology of rabies in Asia and development of new-generation vaccines for rabies

Rabies is an enzootic viral disease widespread throughout the world. Although it is a vaccine-preventable disease, the annual number of human deaths caused by rabies is estimated to be 32,000 in Asia. Phylogenetic analysis based on sequence data of the partial N gene of rabies viruses in Asia has shown that the viruses are divided into five genogroups, distributed in Middle East, South Asia, South East Asia, Malay, and Arctic regions. The genetic relationships among these rabies viruses agree basically with the results of previous studies. Meanwhile, new types of vaccines are being developed by applying gene manipulation techniques to rabies virus in order to overcome the disadvantages of current vaccines. This article reviews the molecular epidemiology of rabies in Asia and progress made in the development of new-generation rabies vaccines with the goal of elimination or control of rabies in Asia.     

Aspergillus carneus M34聚木糖酶与植酸酶同步生产的评估及聚木糖酶最适化生产

半纤维素为自然界中仅次于纤维素的木质纤维素,而聚木糖为农业废弃物中最主要的半纤维素成分,与聚木糖降解有关的酵素总称为聚木糖酶群(xylanolyticenzymes)(Collinsetal.,2005)。植酸(phyticacid)广泛存在于自然界中,植物中的含磷化合物多以此形式存在(Cosgrove,1966),植酸酶(phytase)能将植酸分解成肌醇、肌醇磷酸及无机磷。利用培养条件探讨了同步提升聚木糖酶(xylanase)与植酸酶(phytase)活性的可行性,并以茭白笋壳中获得的半纤维素为碳源,利用反应曲面法进行聚木糖酶的最适化生产。以期了解AspergilluscarneusM34之聚木糖酶与植酸酶2种酵素的生产关系,并对农业废弃物的再利用有所贡献。依据磷源、碳源与实验设计之结果,显示聚木糖酶及植酸酶,在因子种类的选择以及阶层的调整时,无法由同一个因子的改变而达到活性同步提升之目的。中心混成实验所得到的数学模式,平稳点的形式为鞍点,预估的聚木糖酶活性为11.66U/mL;而在聚木糖酶最适化生产上,当碳源为1.5%茭白笋壳半纤维素,氮源为0.8%酵母萃取物与0.4%氯化铵,起始pH值为7.00,于30℃培养5d后,可获得的最大酵素活性为(27.31±1.14)U/mL。     

Competition between 2x and x pollen in styles of Solanum tuberosum determined by a quick in vivo method

Summary Pollen competition in vivo was studied by placing two pollen samples on one stigma and comparing the length of the tubes under a U.V. microscope. Comparisons involving pollen of Solanum tuberosum and S. phureja showed that 2x pollen grew faster than x pollen, both in 2x and x styles. Consequences for induction of dihaploids in S. tuberosum are discussed.     

Protoplast Fusion in the Genus Medicago and Isoenzyme Analysis of Parental and Somatic Hybrid Cell Lines

Leaf mesophyll protoplasts of Medicago arborea (2n = 32) were electrofused with cell suspension and/or callus protoplasts of Medicago sativa. Heterokaryons were identified in agarose beds by their dual fluorescein isothiocianate—chlorophyll fluorescence and their coordinates were recorded. Hybrid minicalli were manually picked up and grown first in nurse culture and then in callus induction medium. Hybrid nature of the selected calli was confirmed by isoenzyme analyses. In order to verify whether morphogenesis of somatic hybrid calli was affected by cell incompatibility, mesophyll and cell suspension protoplasts, derived from the same plant of M. sativa with high embryogenic capacity, were fused. Only callus tissues derived from mesophyll protoplasts retained the highly embryogenic character of the M. sativa genotype, while hybrid cell lines were non-morphogenic and showed isoenzyme patterns similar to tissues derived from cell suspension protoplasts. The achievement of somatic hybrid plants in the genus Medicago is discussed.     

Meiotic restitution mechanisms and 2n pollen formation in a Solanum tuberosum dihaploid and in dihaploid × wild species hybrids*

A Solatium tuberosum dihaploid that proved to be a 2n pollen producer, exhibited two types of meiotic abnormality involved in 2n pollen formation: premature cytokinesis at prophase II and parallel/tripolar spindles in meiosis II. For this reason such a dihaploid was preferentially used as a seed parent in crosses with the diploid species S. tarijense, S. sanctae-rosae, and S. phureja. Diploid interspecific hybrids were evaluated for male fertility, for 2n pollen production and stability over three years and for meiotic nuclear restitution mechanisms. Pollen stainability ranged from 6 to 85% and 2n pollen from 5 to 35% among hybrids. The meiotic mechanism generating 2n pollen was that of spindle abnormality in meiosis II and consequent dyad/triad formation. High correlation was found between fused/parallel spindles and dyads.     

Transmission of resistance to common scab from the diploid to the tetraploid level via 4x-2x crosses in potatoes

Summary Diploid potato clones selected for their reaction to common scab and their ability to produce 2n male gametes were used in a series of crosses to a susceptible tetraploid female parent (cv. Shepody). In addition, two tetraploid clones were also selected for their reaction to common scab and crossed with Shepody as a female parent. Results indicated that resistance to common scab can be effectively transmitted from the diploid to the tetraploid level via 4x-2x crosses. Diploid parents producing 2n pollen via either first division or second division restitution can be used to transmit scab resistance. A relatively small proportion of resistant individuals could be recovered from susceptible x susceptible crosses in both 4x-2x and 4x-4x combinations. The data support a previously developed hypothesis that scab resistance is relatively simply inherited.     

The origin of polyploids via 2n gametes in Vaccinium section Cyanococcus

Summary The production of 2n pollen (pollen with the sporophytic chromosome number) was evaluated in 4x and 6x taxa of Vaccinium section Cyanococcus. Mean frequencies of 2n pollen producers were 17.1% and 8.3% in natural 4x and 6x populations, respectively. The frequency of 2n pollen producers in the 4x species ranged from 8.6% (V. angustifolium) to 23.8% (V. pallidum). Level of 2n pollen production was genotypically variable (1% to 37.4%). The widespread occurrence of 2n pollen in 2x, 4x and 6x taxa suggests that sexual polyploidization was widespread and responsible for the origin of the polyploid species found in this genus. The frequency of 2n pollen producers was not significantly different between the 4x species and their putative 2x ancestors. These results support the origin of 4x and 6x taxa as a consequence of sexual polyploidization. Polyploids derived from sexual polyploidization would be expected to have increased fitness and flexibility due to the mode of 2n pollen formation. In blueberry species the predominant mode of 2n pollen formation is genetically equivalent to a first division restitution mechanism (FDR). FDR 2n pollen transmits a high percentage of the heterozygosity and a large fraction of the epistasis from the 2x parent to the 4x offspring.     

The implications of 2n egg gametes in nobilization and breeding of sugarcane

Summary Nobilization in sugarcane is viewed from a genetic angle considering the significance of 2n gametes. The inbreeding coefficients resulting from 2n gametes, for first and second nobilizations are worked out. The implication of 2n gametes to sugarcane breeding are discussed.     

Bilateral polyploidization inDactylis glomerata L. subsp.lusitanica: occurrence,morphological and genetic characteristics of first polyploids

Summary InDactylis glomerata L. subsp.lusitanica, triploid and tetraploid plants were obtained by bilateral sexual polyploidization in crosses between diploid parents known to produce 2n gametes. The polyploid and diploid progeny were compared for allozyme diversity (allele number and heterozygosity), phenological (pollen fertility, inflorescence emergence date), cellular (stomatic cell size) and morphological characters (vegetative biomass, seed weight, total seed number per plant, panicle number and seed number per panicle length) in four contrasting growing conditions. Stomatal cell size and the total number of alleles were significantly lower in diploids than in polyploids which sometimes recovered more than two distinct alleles at a locus via 2n gametes possessing heterozygous loci. Pollen fertility was similar in diploids and tetraploids, but significantly lower in the triploids. Seed weight was significantly higher in polyploids, although the average number of seeds per panicle length and the total number of seeds was higher in the diploid sibs. No phenological differences occurred among ploidy levels whereas such differences were observed inDactylis in all the natural areas of sympatry between diploids and their related polyploids. Our results provide evidence for an instantaneous effect of polyploidization on certain traits and suggest that natural selection would act subsequently on several other traits to allow the establishment of new polyploids.     

不同基因型苹果的离体再生特性及其对NaN_3的反应

不同基因型苹果叶片培养物再生特性不同，主要表现在再生频率的高低和再生类型的类异，通过培养基中的激素和培养过程的光照调节，可以有效地提高各基因型品种的再生频率。不同基因型苹果叶片培养物对ＮａＮ３诱变处理的反应不同，总体而言，其存活率和再生频率均随ＮａＮ３浓度的提高而下降。不同基因型苹果的适宜ＮａＮ３浓度应有所不同，以３０％存活率为标准，对Ｍ２６、嗄拉，首红，长富２及岩富进行诱变处理的适宜浓度分别为３