尽管草莓镶脉病毒（SVBV）的基因组全序列已经确定，生物信息学分析显示SVBV基因组可编码7个不同的蛋白，但每个蛋白的确切功能并不是非常清楚。在本研究中，我们提供了如下能够验证SVBV编码的P1蛋白（SVBV-P1）所具有的几个特点的证据。利用蛋白定位预测工具分析SVBV-P1蛋白亚细胞定位，共聚焦观察SVBV-P1浸润的本氏烟叶片，结果显示SVBV-P1蛋白定位于本氏烟表皮细胞的细胞质、细胞壁和胞间连丝，还能够在细胞质中形成与微管和内质网相关的包涵体。稀释的SVBV-P1浸润本氏烟叶片，使SVBV-P1蛋白在单细胞表达，结果显示一段时间之后SVBV-P1蛋白能从本氏烟叶片上农杆菌浸润的侵染点细胞转移到邻近的细胞，表明SVBV-P1蛋白具有胞间移动的能力。进一步将稀释的SVBV-P1与马铃薯X病毒（PVX）运动缺陷型突变体共浸润本氏烟叶片，结果显示PVX突变体能从单细胞移动至周围的细胞，表明SVBV-P1蛋白能促进失去运动功能的PVX突变体在本氏烟叶片的细胞间运动。最后，酵母双杂交实验与双分子荧光互补分析显示，SVBV-P1与SVBV-CP共转化的酵母菌能正常生长，SVBV-P1与SVBV-CP共浸润的本氏烟叶片出现荧光，表明SVBV-P1蛋白能与SVBV编码的外壳蛋白互作，而外壳蛋白是花椰菜花叶病毒属病毒粒子的主要成分。电泳迁移率试验测定结果显示，与SVBV-P1蛋白孵育的DNA在电泳过程中并未出现阻滞，说明SVBV-P1蛋白缺乏结合DNA的能力。综上所述，我们的研究结果表明SVBV-P1蛋白很可能是SVBV的运动蛋白，并且为进一步研究花椰菜花叶病毒属病毒的运动蛋白功能提供了新的思路。

The East Eurasian Steppe Transect (EEST) is the first international transect across regions of middle and high latitudes in the eastern Eurasian steppe. The EEST is an ideal platform for researching the response of Eurasian temperate steppe to global change, because of its integrated gradients of temperature and human activities on a large-scale. In this study, basic characteristics of plant communities along the EEST across a latitudinal gradient was analyzed. According to the survey of 58 sampling sites, there are 140 species belonging to 34 families and 94 genera. Of particular note was the finding of Astragalus dalaiensis which has disappeared in the grasslands of China. On the whole, Gramineae plants are dominant with Liliaceae plants in the communities significantly decreasing along the latitudinal gradient from south to north. The Shannon-Wiener index and biomass of communities all decreased along the latitudinal gradient with significant negative linear regressions. The SDR2 (summed dominance ratio based on two factors) of dominant plants in the upper layers of communities, such as Stipa and Leymus chinensis, decreased along the latitudinal gradient from south to north. Especially, the SDR2 of L. chinensis decreased significantly. The SDR2 of Cleistogenes squarrosa, Agropyron cristatum in the lower layers of communities and the indicator species for degradation were not affected. Potentilla acaulis was found mainly in the southern and northern areas. Stellera chamaejasme was found just in a few sites in the southern area of the EEST. In communities of Stipa grandis and Stipa krylovii, annual and biennial species are dominant. The ratio of annual and biennial species in the community is significantly related to the latitudinal gradient. Perennial herbaceous plants and shrubs were not affected. According to the principal component analysis (PCA), with the data from 58×140 dimensions, the first and second components had the lowest proportion, thus indicating that the species compositions and community structures are homogeneous along the EEST. There is a certain degree of spatial differentiation along the EEST due to degradation’s differences resulting from the different land uses.

The reverse genetics for classical swine fever virus (CSFV) is currently based on the transfection of in vitro transcribed RNA from a viral genomic cDNA clone, which is inefficient and time-consuming. This study was aimed to develop an improved method for rapid recovery of CSFV directly from cloned cDNA. Full-length genomic cDNA from the CSFV Shimen strain, which was flanked by a T7 promoter, the hepatitis delta virus ribozyme and T7 terminator sequences, was cloned into the lowcopy vector pOK12, producing pOKShimen-RzT . Direct transfection of pOKShimen-RzT into PK/T7 cells, a PK-15- derived cell line stably expressing bacteriophage T7 RNA polymerase, allowed CSFV to be rescued rapidly and efficiently, i.e., at least 12 h faster and 31.6-fold greater viral titer when compared with the in vitro transcription-based rescue system. Furthermore, the progeny virus rescued from PK/T7 cells was indistinguishable, both in vitro and in vivo, from its parent virus and the virus rescued from classical reverse genetics. The reverse genetics based on intracellular transcription is efficient, convenient and cost-effective. The PK/T7 cell line can be used to rescue CSFV directly from cloned cDNA and it can also be used as an intracellular transcription and expression system for studying the structure and function of viral genes.

To develop a modified live vaccine (MLV) against porcine reproductive and respiratory syndrome virus (PRRSV), virulent CH-1a strain was attenuated by serial passages up to 130 passage (P130) in Marc-145 cells. The virulence and immune efficacy of the attenuated CH-1a were evaluated in pigs. The results showed that animals inoculated with P130 did not develop any clinical sign of the disease, but produced rapid and effective humoral immune responses against PRRSV challenge, indicating that attenuated CH-1a P130 is the candidate as the effective vaccine against PRRSV. To define the potential mutations in the attenuated CH-1a genome, we sequenced and analyzed the ORF5 gene of CH-1a strain of different passages (P39, P55, P65, P70, P85, P100, P115, P120, P125, and P130) and found that three mutations (C5Y, H38Q and L146Q) which may be related with the attenuation of CH-1a. In addition, we also found a unique restriction enzyme site (TspEI) in the ORF5 gene of attenuated CH-1a, which can be used as a genetic marker to distinguish original and attenuated CH-1a.