Lianhui Xie

Pc4, a putative movement protein of Rice stripe virus, interacts with a type I DnaJ protein and a small Hsp of rice

Rice stripe virus (RSV) infects rice and causes great yield reduction in some Asian countries. In this study, rice cDNA library was screened by a Gal4-based yeast two-hybrid system using pc4, a putative movement protein of RSV, as the bait. A number of positive colonies were identified and sequence analysis revealed that they might correspond to ten independent proteins. Two of them were selected and further characterized. The two proteins were a J protein and a small Hsp, respectively. Interactions between Pc4 and the two proteins were confirmed using coimmunoprecipitation. Implications of the findings that pc4 interacted with two chaperone proteins were discussed.

Complete genome analysis of a novel recombinant isolate of potato virus Y from China.

The complete sequence of GF_YL20, a potato virus Y (PVY) isolate from China, encodes a polyprotein of 3,061 amino acids. Sequence analysis indicates that GF_YL20 has a genomic structure different from previously reported PVY strains. It shares 99xa0% nucleotide sequence identity with PB209 (PVYN:O) except in VPg, but more than 97xa0% nucleotide sequence identity with the VPg of Mont (PVYN), PB312 (PVYNTN) and HN2 (SYR-I). Phylogenetic analysis indicates that GF_YL20 is a novel N:O recombinant with three recombination breakpoints.

Structure-Activity Relationship of Triterpenes and Triterpenoid Glycosides against Tobacco Mosaic Virus

A new activity of triterpenes and triterpenoid glycosides against phytovirus has been found. Based on the anti-TMV replication activity in vivo, 47 triterpenes and triterpenoid glycosides were screened through the leaf-disk method together with indirect ELISA. Structure-activity relationships were analyzed according to the results of bio-activity screening. Besides, the EC(50) values of those compounds having higher activities were measured.

A new phenolic glycoside and cytotoxic constituents from Celosia argentea

A new phenolic glycoside, 4-O-β-D-apifuranosyl-(1 → 2)-β-D-glucopyranosyl-2-hydroxy-6-methoxyacetophenone (2) and 11 known compounds were isolated from the MeOH extract of the plant Celosia argentea. The structures of the compounds were elucidated on the basis of spectroscopic analysis and chemical methods. Among the isolated compounds, stigmasterol (10) showed moderate inhibitory activities against SGC-7901 and BEL-7404 cells.

Complete genome sequence of a novel monopartite geminivirus identified in mulberry ( Morus alba L.)

The genome sequence of a novel geminivirus from mulberry samples exhibiting crinkle leaf symptoms is reported. The sequence consisted of 2952 nt, containing four open reading frames (ORFs) in the viral-sense strand and two ORFs in the complementary-sense strand. The size of the genome and the conserved origin of replication are similar to those of members of the family Geminiviridae, but the genomic organization, number of ORFs, and especially five contiguous GAAAAA repeats positioned upstream of ORF1 distinguish it from other geminiviruses. Phylogenetic analysis coupled with ORF analysis suggests that this is a novel virus that does not fit into the established seven genera of the family Geminiviridae. The virus, found in Zhenjiang, Jiangsu province, China, is tentatively named mulberry crinkle leaf virus isolate Jiangsu (MCLV-js).

Adaptive evolution and demographic history contribute to the divergent population genetic structure of Potato virus Y between China and Japan

Potato virus Y (PVY) is an important plant pathogen causing considerable economic loss to potato production. Knowledge of the population genetic structure and evolutionary biology of the pathogen, particularly at a transnational scale, is limited but vital in developing sustainable management schemes. In this study, the population genetic structure and molecular evolution of PVY were studied using 127 first protein (P1) and 137 coat protein (CP) sequences generated from isolates collected from potato in China and Japan. High genetic differentiation was found between the populations from the two countries, with higher nucleotide diversity in Japan than China in both genes and a KST value of .216 in the concatenated sequences of the two genes. Sequences from the two countries clustered together according to their geographic origin. Further analyses showed that spatial genetic structure in the PVY populations was likely caused by demographic dynamics of the pathogen and natural selection generated by habitat heterogeneity. Purifying selection was detected at the majority of polymorphic sites although some clade‐specific codons were under positive selection. In past decades, PVY has undergone a population expansion in China, whereas in Japan, the population size of the pathogen has remained relatively constant.

Molecular characterization and detection of a recombinant isolate of bamboo mosaic virus from China

The complete genome sequences of three isolates of bamboo mosaic virus (BaMV) from mainland China were determined and compared to those of BaMV isolates from Taiwan. Sequence analysis showed that isolate BaMV-JXYBZ1 from Fuzhou shares 98xa0% nucleotide sequence identity with BaMV-YTHSL14 from nucleotides 2586 to 6306, and more than 94xa0% nucleotide sequence identity with BaMV-MUZHUBZ2 in other regions. Recombination and phylogenetic analyses indicate that BaMV-JXYBZ1 is a recombinant with one recombination breakpoint. To our knowledge, this is the first report of a BaMV recombinant worldwide.

Expression of rice gall dwarf virus outer coat protein gene (S8) in insect cells.

To obtain the P8 protein of Rice gall dwarf virus (RGDV) with biological activity, its outer coat protein gene S8 was expressed in Spodoptera frugiperda (Sf9) insect cells using the baculovirus expression system. The S8 gene was subcloned into the pFastBac™1 vector, to produce the recombinant baculovirus transfer vector pFB-S8. After transformation, pFB-S8 was introduced into the competent cells (E. coli DH10Bac) containing a shuttle vector, Bacmid, generating the recombinant bacmid rbpFB-S8. After being infected by recombinant baculovirus rvpFB-S8 at different multiplicities of infection, Sf9 cells were collected at different times and analyzed by SDS-PAGE, Western blotting and immunofluorescence microscopy. The expression level of the P8 protein was highest between 48–72 h after transfection of Sf9 cells. Immunofluorescence microscopy showed that P8 protein of RGDV formed punctate structures in the cytoplasm of Sf9 cells.

A new nepovirus identified in mulberry (Morus alba L.) in China

An isometric virus was identified in mulberry leaves showing symptoms of mulberry mosaic leaf roll (MMLR) disease. Its genome consists of two (+)ssRNAs. RNA1 and RNA2 have 7183 and 3742 nucleotides, excluding the 3′-terminal poly(A) tail. Based on phylogenetic analysis of the RNA1-encoded polyprotein and CP amino acid sequences, the properties of the the 3′-UTR of RNA1 and RNA2, and <75xa0% identity in the CP amino acid sequence, this virus is proposed to be a new member of the genus Nepovirus, subgroup A. Since a causal relationship between this virus and MMLR has not been established, it is tentatively referred to as MMLR-associated virus.

Sequence variation and protein structure of pipo gene in Potato virus Y: Sequence variation and protein structure of pipo gene in Potato virus Y

The objectives of this study were to understand the sequence variation and the putative protein structure of pipo gene in the Potato virus Y (PVY) collected from Solanum tuberosum. The pipo gene in PVY was cloned using a pair of degenerate primers designed from its conserved region and its sequences were used to re-construct phylogenetic tree in Potyvirus genera by a Bayesian inference method. An expected fragment of 235 bp was amplified in all 20 samples by RT-PCR and the pipo genes in the 20 samples assayed shared more than 92% nucleotide sequence similarity with the published sequences of PVY strains. Among the 20 pipo gene sequences, 13 polymorphic sites were detected, including 4 parsimony informative sites and 9 singleton variable sites. These results indicate that PVY pipo gene is highly conserved but some sequence variations exist. Further analyses suggest that the pipo gene encodes a hydrophilic protein without signal peptide and transmembrane region. The protein has theoretical isoelectric points (pI) ranging from 11.26 to 11.62 and contains three highly conserved regions, especially between aa 10 and 59. The protein is likely located in the mitochondria and has a-helix secondary structure. Bayesian inference of phylogenetic trees reveals that PVY isolates are clustered in the same branch with high posterior probability, while Sunflower chlorotic mottle virus (SoCMoV) and Pepper severe mosaic virus (PepSMV) are closely related, consisting with the classification of Potyvirus genera using other approaches. Our analyses suggest that the pipo gene can be a new marker for phylogenetic analysis of the genera. The results reported in this paper provide useful insights in the genetic variation and the evolution of PVY and can stimulate further research on structure and function of the PIPO protein.