Principles of Molecular Organization, Expression, and Evolution of Closteroviruses: Over The Barriers

The 5h-terminal genomic region (8597 nt) of little cherry virus (LChV), a mealybug-borne closterovirus, was cloned from double-stranded RNA, and its sequence determined to complete the 16 934 nt sequence of the monopartite LChV RNA genome. In the 5h to 3h direction, the sequence encompasses ORF 1a, encoding the conserved replicative domains of methyltransferase and helicase, and ORF 1b, encoding RNA polymerase. ORFs 1a and 1b partially overlap (in 0/M 1 configuration), and the LChV replicase is probably expressed by ribosomal frameshifting as a fusion product with a molecular mass of 318 kDa. The N-terminal part of the ORF 1a product contains a papain-like cysteine proteinase (PCP) domain with a predicted cleavage site between Gly-619 and Ser-620. The PCP and the upstream protein domains can be aligned with the equivalent parts of the leader proteins encoded by the whitefly-transmitted lettuce infectious yellows and sweet potato sunken vein closteroviruses. Phylogenetic reconstruction based on the aligned RNA polymerase sequences clearly suggests that the aphid-transmissible and whiteflytransmissible closteroviruses represent two distinct evolutionary lineages, with the mealybug-transmissible LChV being the most remote member of the ' whitefly ' lineage.Little cherry disease (LCD) is distributed worldwide in ornamental and sweet cherry and has a great impact on the fruit quality of infected trees. In infected phloem cells,

mentioning

confidence: 74%

“…5h-proximal replication-associated genes is seen in the other closterovirus genomes so far sequenced, and it has been suggested that closterovirus replicases are expressed by j1 ribosomal frameshifting (reviewed in Agranovsky, 1996). If frameshift occurs at the ORF 1a stop codon, a 1ab fusion protein consisting of 2807 aa (M r 317 548) would be produced.…”

mentioning

confidence: 99%

Complete genome structure and phylogenetic analysis of little cherry virus, a mealybug-transmissible closterovirus.

Wilhelm¹,

Fechtner

Agranovsky³

1997

“…The plant virus family Closteroviridae was established to include only those viruses with flexuous filamentous particles longer than 1000 nm (Dolja et al, 1994 ;Agranovsky, 1996). Two genera have been proposed.…”

Section: Introductionmentioning

confidence: 99%

“…Other aphid-or whitefly-transmissible closteroviruses generally have a smaller coat protein, ranging from 22 to 26 kDa (Dolja et al, 1994 ;Agranovsky et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Nucleotide sequence of the 3'-terminal two-thirds of the grapevine leafroll-associated virus-3 genome reveals a typical monopartite closterovirus.

Ling¹,

Zhu²,

Drong³

et al. 1998

“…

Citrus tristeza virus (CTV), a member of the closterovirus group (Agranovsky, 1996 ;Bar-Joseph et al, 1995 ;Dolja et al, 1994 ;Coffin & Coutts, 1993), is one of the most destructive pathogens of citrus, causing a range of diseases such as quick decline and stem-pitting in susceptible cultivars. A large number of CTV strains or isolates has been characterized differing in symptomatology and serological properties (BarJoseph et al, 1989).

…”

mentioning

confidence: 99%

A cDNA clone from a defective RNA of citrus tristeza virus is infective in the presence of the helper virus.

Yang

Mawassi

Ashoulin

et al. 1997

Citrus tristeza virus (CTV), a member of the closterovirus group (Agranovsky, 1996 ;Bar-Joseph et al., 1995 ;Dolja et al., 1994 ;Coffin & Coutts, 1993), is one of the most destructive pathogens of citrus, causing a range of diseases such as quick decline and stem-pitting in susceptible cultivars. A large number of CTV strains or isolates has been characterized differing in symptomatology and serological properties (BarJoseph et al., 1989). The CTV virions are heterodimers and, similarly to beet yellows virus (Agranovsky et al., 1995), consist of two segments ; the larger, ca. 2000 nm, is encapsidated by the p25 coat protein (CP) and the shorter, ca. 75-85 nm, is encapsidated by p27, a diverged coat protein (CPd) (Febres et al., 1996). The CTV particles contain a single component positive-stranded genomic RNA, of 19 296 nt for the T-36 strain from Florida and of 19 226 nt for the Israeli strain VT (Mawassi et al., 1996). The genomes of these strains showed considerable Author for correspondence : Moshe Bar-Joseph.Fax j972 3 9604180. e-mail vpmbj!volcani.agri.gov.il sequence deviation within the 5h half, but were found to have similar organization and to encompass 12 ORFs, which potentially code for at least 17 protein products, including the replication associated proteins, a homologue of the HSP70 proteins and the two coat proteins Mawassi et al., 1996). In addition to the genomic and subgenomic RNAs plants infected with CTV contain multiple species of defective RNAs (D-RNAs). These D-RNAs consist of the 5h-and 3h-terminal segments of the genomic RNA, with extensive internal deletions. Hybridization analysis showed that the DRNAs are abundant in infected plants and occur in most CTV isolates (Mawassi et al., 1995 b, c). Two of the characterized CTV VT D-RNAs of 2n7 and 4n5 kb were found to represent different fusions of the genomic termini, whereas the 2n4 kb D-RNA molecule contained a short nonviral segment of 14 nt at the junction site (Mawassi et al., 1995 b, c). The 2n4 kb dsRNA band, previously shown to contain the 2424 nt D-RNA (Mawassi et al., 1995 b), was later found to contain a second molecule, designated D2.3-RNA, of 2379 nt, structurally representing a fusion of 1521 nt and 858 nt from the 5h and 3h ends, respectively, of CTV-VT. The present paper reports the cloning and sequence characterization of a new D-2.3 RNA and its use for the construction of an infectious cDNA clone.CTV strains VT (Mawassi et al., 1996) and GalT (obtained from Mr Yair Oren, Department of Citriculture, Ministry of Agriculture, Israel), were propagated in Alemow (Citrus macrophylla) seedlings. Total single-stranded RNA (ssRNA) was extracted from the leaves and young bark of infected plants using Tri-Reagent (Molecular Research Center Inc.). Double-stranded (ds) RNA was isolated from bark tissue according to Dodds & Bar-Joseph (1983). The dsRNA molecules were separated by PAGE. The 2n3 kb dsRNA segments were isolated by electroelution using Bio-Trap membranes (Schleicher and Schuell), or by elution into 0n5iTBE buffer (Mania...