Tomato yellow leaf curl virus: A whitefly-transmitted geminivirus with a single genomic component

Abstract

The genome of the tomato yellow leaf curl virus (TYLCV), a Bemisia tabaci-transmitted geminivirus, was cloned. All clones obtained were of one genomic molecule, analogous to DNA A of African cassava mosaic virus. Nucleotide sequence analysis of the TYLCV genome showed that it comprises 2787 nucleotides, encoding six open reading frames, two on the virion strand and four on the complementary strand. All of them have counterparts in other geminiviruses. Dimeric copies of the cloned viral genome were introduced into tomato plants by agroinoculation. Severe yellow leaf curl disease symptoms developed in all of them. Effective whitefly-mediated transmission of the virus from agroinoculated plants to test plants demonstrated that the cloned molecule carries all the information needed for virus replication, systemic infection, and transfer by whiteflies. Restriction and hybridization analyses of viral DNA forms in infected plants and viruliferous whiteflies did not support the presupposed existence of a second genomic component. This is the first report of a whitefly-transmitted geminivirus that possesses a single genomic molecule.

Complete nucleotide sequence of the geminivirus tomato yellow leaf curl virus, Thailand isolate

“…Agroinoculation of tomato with TYLCV-I and TYLCV-S resulted in symptoms and viral DNA accumulation that was indistinguishable from natural infection. Furthermore, in these studies whiteflies effectively transmitted the disease from agroinoculated plants to healthy plants (Navot et al, 1991 ;Kheyr-Pour et al, 1991). The genome of TLCV is a single DNA molecule which is infectious on tomato following agroinoculation of a dimer construct .…”

“…After the complete sequence of the TYLCV-Th genome had been derived, further analysis was carried out using sequence analysis software from DNASTAR Inc. Optimal alignments (pairwise and multiple) and estimating degrees of sequence identity between analogous DNA and predicted protein sequences of specific geminiviruses were made using the Megalign program. Geminiviruses used for the comparative analyses included: TYLCV-Th, TYLCV-I (Navot et al, 1991), TYLCV-S (Kheyr-Pour et al, 1991), TLCV , ACMV (Stanley & Gay, 1983), TGMV (Hamilton et al, 1984), BGMV (Howarth et al, 1985), squash leaf curl virus (SqLCV) (Lazarowitz & Lazdins, 1991), Chloris striate mosaic virus (CSMV; Andersen et al, 1988), MSV (Mullineaux et al, 1984), wheat dwarf virus (WDV) (MacDowell et al, 1985), Digitaria streak virus (DSV) (Donson et al, 1987), abutilon mosaic virus (AbMV) (Frischmuth et al, 1990) and BCTV (Stanley et al, 1986). The sequences of the intergenic regions of bean dwarf mosaic virus (BDMV; Gilbertson et al, 1991a) and tomato mottle virus (TMoV; Gilbertson et al, 1991b) were retrieved from the GenBank Sequence Database (accession numbers M88179 and M90494, respectively).…”

“…Another study identified subsets of viruses within this subgroup according to geographical distribution with BGMV and tomato golden mosaic virus (TGMV) as examples of 'New World" geminiviruses and African cassava mosaic virus (ACMV) and tomato yellow leaf curl virus (TYLCV) as 'Old World' geminiviruses (Howarth & Vandemark, 1989). More recently, several isolates of whitefly-transmitted geminiviruses have been described which infect tomato plants and contain only a single DNA component (Navot et al, 1991;Kheyr-Pour et al, 1991;Dry et al, 1993). These geminiviruses include two isolates of TYLCV, isolated in Israel (TYLCV-I) and Sardinia (TYLCV-S), as well as tomato leaf curl virus (TLCV) from Australia.…”

Replication promiscuity of DNA-β satellites associated with monopartite begomoviruses; deletion mutagenesis of the Ageratum yellow vein virus DNA-β satellite localizes sequences involved in replication

“…However, since the characterization of tomato yellow leaf curl virus and tomato yellow leaf curl Sardinia virus (Kheyr-Pour et al, 1991;Navot et al, 1991), a large number of begomoviruses have been isolated for which only a single genomic component, equivalent to DNA-A, has been identified (Stanley et al, 2005). Many of these apparently monopartite begomoviruses are associated with a small satellite, designated DNA-b, which is essential for maintenance of the disease.…”

Pathogenicity of a naturally occurring recombinant DNA satellite associated with tomato yellow leaf curl China virus

“…Both components of the bipartite begomoviruses are required for systemic infection and symptom induction (Stanley, 1983). For some monopartite begomoviruses, such as tomato yellow leaf curl virus (Navot et al, 1991) and tomato leaf curl virus (Dry et al, 1993), the single DNA component is sufficient to produce disease symptoms. However, this is not the case for other monopartite begomoviruses such as Ageratum yellow vein virus (AYVV), Bhendi yellow vein mosaic virus, cotton leaf curl Multan virus, Eupatorium yellow vein virus and tomato yellow leaf curl China virus (TYLCCNV).…”