Messenger RNA for the coat protein of tobacco mosaic virus.

TMV RNA is not an efficient template for translation of the viral coat protein, in spite of containing nucleotide sequences coding for the protein. Efficient translation requires the prior synthesis within infected cells of a smaller RNA carrying only a portion of the information encoded in the whole genome.     

Two-step binding of eukaryotic ribosomes to brome mosaic virus RNA3

Although brome mosaic virus RNA3 has only one translatable cistron, it can bind two 80S ribosomes at initiation. One ribosome binds at the first AUG codon (base 92-94). The other binds nearer the 5' end at an entry or holding site. Disome formation is thus unrelated to a silent cistron approximately 1,000 bases downstream.     

六安地区高粱花叶病毒P3基因的克隆和序列测定

从六安产甘蔗病叶中提取总RNA,逆转录获得甘蔗花叶病毒(Sorghun mosaic virus,SrMV)基因组cDNA。设计P3基因特异引物,通过PCR扩增P3基因,并将P3基因cDNA克隆、测序。     

Nucleotide sequence of RNA2 and polyprotein processing sites of a Chinese isolate of broad bean wilt virus 2

RNA2 of broad bean wilt virus 2 (BBWV2) isolate B935 is composed of 3601 nucleotide (nt) residues, exclusive of the polyadenylate at the 3' end. Only one of the six possible reading frames has a long open reading frame, which extends from nt 231 to nt 3428 in the polarity of encapsidated RNA, and encodes a polyprotein of 119 kD. The N-terminus of the large coat protein (LCP) is located at 599 nt and the small coat protein (SCP) at 197 nl from the C-terminus of the 119 kD protein, which suggests that the coat proteins are released from the polyprotein by cleavages of a glulamine-glycine (Q-G) and a glutamine-alanine (Q-A) bond respectively. The sequence comparison of B935 with fabaviruses shows that B935 has very high sequence homology with other BBWV2 isolates and with patchoul' mild mosaic virus, but has lower homology with BBWV1 isolates. B935 has a similar genomic organization, but a low sequence homology to RNA2 molecules of comoviruses and nepoviruses.     

A new satellite to satellite tracking algorithm from Doppler-shifted frequency measurements

A new satellite to satellite tracking (SST) algorithm from Doppler-shifted frequency measurements is proposed. The estimation principle is demonstrated and the mathematic model of SST is established. The state estimation methods for a user (the cooperative case) and target satellites (the non-cooperative case) are presented based on particle swarm optimization (PSO). The Cramer-Rao lower bounds (CRLB) are deduced as well. Performance of the new algorithm is validated through computer simulations, which proved that the proposed method is effective in terms of the estimation quality compared with CRLB and superior in accuracy to the Bearings-Only (BO) method in almost all simulation cases except for the case that an enough long tracking arc-length is obtained for a user satellite.     

Malvastrum yellow vein virus,a new Begomovirus species associated with satellite DNA molecule

Virus isolate Y47 was obtained from Malvastrum coromandelianum showing yellow vein symptom in Honghe, Yunnan Province. The complete nudcotide sequence of DNA-A was determined, it contains 2731 nuclcotides,having typical genomic organiTation of a begomovirns, encoding 6ORFs with 2ORFs [AVI(CP) and AV2] in virionsense DNA and 40RFs (ACl-AC4) in complementary-sense DNA. Comparisons show that the total DNA-A of Y47 has the highest sequence identity (77%) with that of Okra yellow vein mosaic virus-[201] (AJ002451), while less than 76% identities are found when compared with other begomoviruses. The molecular data show that virus isolate Y47 is a distinct begomovirns species, for which the name Maivastrum yellow vein vorus is proposed. Satellite DNA molecule (Y47β) was found to be associated with Y47 using the primers (beta01 and beta02) specific for DNAβ Y47β consists of 1348 nuclcotides, with a functional ORF (CI) in complemen-tary-sense DNA.Y47β has 62%--67% sequence identity with DNAβ molecule associated with Cotton leaf curl Muitan virus or Cotton leaf curl Rajasthan virus, while lower than 46% sequence identities are found when compared with other reported DNA[~ molecules. Relationship dendrograms show that DNAβ molecules are co-evolved with their help begomoviruses.     

A new satellite to satellite tracking algorithm from Doppler-shifted frequency measurements

A new satellite to satellite tracking (SST) algorithm from Doppler-shifted frequency measurements is proposed. The estimation principle is demonstrated and the mathematic model of SST is established. The state estimation methods for a user (the cooperative case) and target satellites (the non-cooperative case) are presented based on particle swarm optimization (PSO). The Cramer-Rao lower bounds (CRLB) are deduced as well. Performance of the new algorithm is validated through computer simulations, which proved that the proposed method is effective in terms of the estimation quality compared with CRLB and superior in accuracy to the Bearings-Only (BO) method in almost all simulation cases except for the case that an enough long tracking arc-length is obtained for a user satellite.     

Synthesis of brome mosaic virus subgenomic RNA in vitro by internal initiation on (-)-sense genomic RNA

The genomes of many (+)-stranded RNA viruses, including plant viruses and alphaviruses, consist of polycistronic RNAs whose internal genes are expressed via subgenomic messenger RNAs. The mechanism(s) by which these subgenomic mRNAs arise are poorly understood. Based on indirect evidence, three models have been proposed: (1) internal initiation by the replicase on the (-)-strand of genomic RNA, (2) premature termination during (-)-strand synthesis, followed by independent replication of the subgenomic RNA and (3) processing by nuclease cleavage of genome-length RNA. Using an RNA-dependent RNA polymerase (replicase) preparation from barley leaves infected with brome mosaic virus (BMV) to synthesize the viral subgenomic RNA in vitro, we now provide evidence that subgenomic RNA arises by internal initiation on the (-)-strand of genomic RNA. We believe that this also represents the first in vitro demonstration of a replicase from a eukaryotic (+)-stranded RNA virus capable of initiating synthesis of (+)-sense RNA.