RNA干扰抑制家畜病毒感染的研究进展

RNAi(RNA-mediated interference)是一种由序列特异性的dsRNA(double stranded RNA)作为触发器来触发同源mRNA降解从而引起基因沉默的细胞机制。利用RNAi方法可以通过沉默特异基因来对目的基因进行功能性分析,另外通过干扰RNA抑制病原性基因的表达来进行病毒性疾病治疗的研究已取得了显著的成就。作者对RNAi的作用机制、RNAi在抑制病毒复制和抵抗病毒感染动物方面的研究进展及应用前景和存在问题进行了综述。     

Ear Rot Susceptibility and Mycotoxin Contamination of Maize Hybrids Inoculated with Fusarium Species Under Field Conditions

The development of new maize hybrids with resistance to Fusarium infection is an effective means of minimizing the risk of mycotoxin contamination. Several maize hybrids have been investigated for Fusarium ear rot and accumulation of fumonisin B₁ (FB₁), fumonisin B₂ (FB₂), beauvericin (BEA) and fusaproliferin (FP) after artificial inoculation in the field with toxigenic strains of Fusarium verticillioides and Fusarium proliferatum. The year of inoculation had a significant influence on the disease severity and mycotoxin accumulation in maize kernels. Of all the hybrids tested, only Mona exhibited resistance to ear rot caused by F. verticillioides and produced low levels of fumonisins during three years of experiments. In Fusarium-damaged kernels (FDK), fumonisin B₁, fumonisin B₂, beauvericin and fusaproliferin were detected at concentrations much higher (up to 10–20 times) than in healthy-looking kernels (HLK). Animal and human exposure to these mycotoxins can be drastically reduced by removing mouldy and visibly damaged kernels from the commodity.     

大麦黄矮病毒GPV与GAV株系间异源装配现象的初步研究

 以我国麦区的大麦黄矮病毒GPV、GAV株系为材料,利用它们的蚜传特异性,将由禾谷缢管蚜传播的GPV和由麦长管蚜传播的GAV混合侵染到岸黑燕麦上,并进行继代传毒。混合侵染后代蚜传表现型的变化初步表明存在异源装配现象,且表现型混合发生的比例较高。用DAS-ELISA和RT-PCR法对混合侵染后代进行了测定,进一步证明了异源包装现象的存在。部分基因的核苷酸序列分析初步显示所测定的混合侵染后代中没有发生基因重组。     

The role of seeds and airborne inoculum in the initiation of leaf blotch (Rhynchosporium secalis) epidemics in winter barley

Both airborne spores of Rhynchosporium secalis and seed infection have been implied as major sources of primary inoculum for barley leaf blotch (scald) epidemics in fields without previous history of barley cropping. However, little is known about their relative importance in the onset of disease. Results from both quantitative real‐time PCR and visual assessments indicated that seed infection was the main source of inoculum in the field trial conducted in this study. Glasshouse studies established that the pathogen can be transmitted from infected seeds into roots, shoots and leaves without causing symptoms. Plants in the field trial remained symptomless for approximately four months before symptoms were observed in the crop. Covering the crop during part of the growing season was shown to prevent pathogen growth, despite the use of infected seed, indicating that changes in the physiological condition of the plant and/or environmental conditions may trigger disease development. However, once the disease appeared in the field it quickly became uniform throughout the cropping area. Only small amounts of R. secalis DNA were measured in 24 h spore‐trap tape samples using PCR. Inoculum levels equivalent to spore concentrations between 30 and 60 spores per m³ of air were only detected on three occasions during the growing season. The temporal pattern and level of detection of R. secalis DNA in spore tape samples indicated that airborne inoculum was limited and most likely represented rain‐splashed conidia rather than putative ascospores.     

栗疫病菌侵染板栗枝条的显微观察

栗疫病是一种严重危害栗属植物的病害。为了明确栗疫病菌侵染板栗枝条的过程及侵染的关键时间点,本研究利用病理组织切片技术、显微镜和扫描电镜技术对栗疫病菌侵染板栗枝条的过程进行了观察。结果表明:接种栗疫病菌后0～5 h,菌丝先降解枝条表皮,进行横向营养生长的同时沿着伤口纵向侵染,为进入皮层做准备;接种后6 h病菌开始在表皮定殖,并侵入皮层;接种后9 h在皮层可观察到侵染性菌丝沿着细胞间隙向相邻细胞延伸;接种后12 h栗疫病菌侵入韧皮部,在皮层的侵染面积扩大。随着侵染程度加深,皮层、韧皮部等处细胞被菌丝降解,最终在形成层附近聚集。接菌后9 h为栗疫病菌侵染板栗枝条的关键时间点。     

Conidial density of <Emphasis Type="Italic">Monilinia</Emphasis> spp. on peach fruit surfaces in relation to the incidences of latent infections and brown rot

To evaluate the effect of conidial density of Monilinia spp. on the fruit surface on the incidence of latent infection and brown rot in peaches, eleven field surveys were performed in commercial orchards located in Cataluña, Spain over four growing seasons from 2002 to 2005, and nine surveys were conducted to determine the sources of overwintered Monilinia spp. inoculum. There was a significant positive relationship (r?=?0.69) between the numbers of conidia of Monilinia spp. on the fruit surface and the incidence of latent infections, but not with brown rot at harvest. Although mummified fruit, twigs and pits have been identified as being able to carry the pathogen from year to year in peaches grown in Spanish orchards, no relationships between any of these sources and the numbers of conidia on the fruit surface, or incidence of latent infection or brown rot were found. The effect of temperature (T), solar radiation (SR), rainfall (R) and wind speed (WS) on the area under the number of conidia of Monilinia spp. curve (AUncC) on peach surfaces was analysed. Regression analysis revealed that T, SR, R, and WS could account for 99% of the total variation in the area of the AUncC on peach surfaces. Thus, in order to reduce the incidence of latent infection and brown rot it is essential not only to remove the sources of primary inoculum but also to reduce the number of Monilinia spp. conidia on the fruit surface. Furthermore, the sources of airborne conidia of Monilinia spp. should be taken into consideration in disease management programmes in Spain.     

核多角体病毒侵染棉铃虫中肠细胞的观察

应用电子显微镜技术观察了核多角体病毒入侵棉铃虫中肠细胞及其增殖和释放，经口接种后30min，有许多病毒粒子进入中肠后部柱状细胞的微绒毛间隙处，且以其粒子的一端与微绒毛接触并吸附在微绒毛表面上，接种后1h，病毒粒子的囊膜与微绒毛的质膜以顶端对顶端、顶端对侧面发生融合，仅以核衣壳侵入细胞内，然后又继续移至微绒毛底部，从而进入中肠细胞内，此外，还发现有的病毒粒子直接与柱状细胞的质膜融合，侵入中肠细胞，在中肠细胞内增殖的病毒极少观察到被囊膜包住。     

Implications of bacterial contaminated seed lots and endophytic colonization by Pseudomonas fuscovaginae on rice establishment

The economic impact of seedborne bacterial diseases on rice production provides a major motivation for research on seed health. This paper reports on the endophytic growth of a rifampicin‐marked strain of the seedborne rice pathogen Pseudomonas fuscovaginae. The bacterium was found in most tested seeds indicating that, even without visible discolouration, seed transmission is possible. Crushed discoloured seeds contained more bacterial cells than did non‐crushed discoloured seeds. These bacteria were released during seed soaking, contaminating clean seed and lowering seed germination. Cells of a rifampicin‐resistant strain of P. fuscovaginae, which had been inoculated onto rice seeds, were subsequently recovered from different growth stages and from different rice tissues, thereby indicating endophytic colonization. These results have implications for seedling establishment, as symptomless seeds do not assure disease‐free seeds, and the presence of seedborne bacteria results in poor germination and poor seedling establishment. Elimination of seedborne bacteria by soaking in sodium hypochlorite can increase seed germination. This could be used in developing control strategies, and, if practised regularly, reduce entry of seedborne disease‐causing organisms into crops, resulting in lower disease pressure.     

噬菌体在苏云金芽孢杆菌发酵中的感染因素

采用4类噬菌体对9株不同血清型苏云金杆菌菌株进行了敏感试验。结果表明，不同菌株敏感性差异较大，其中CZE99985菌株在35～37℃下对4种噬菌体具有明显的抗性。通过对噬菌体的侵入时间和侵入量的测定，结果表明噬菌体侵入时间越早，侵入量越高，其感染造成的危害越大。培养12h前，接入一定量的TP-1型噬菌体会导致发酵异常；在发酵初期，侵入量达到0．5ml（4PFUs／m1）以上便发生严重的感染现象。