Characterization of DNAβ associated with begomoviruses in China and evidence for co-evolution with their cognate viral DNA-A FN1

Abstract

Eighteen samples of begomoviruses isolated from tobacco, tomato and weed species in Yunnan, China were found to be associated with DNAb molecules, for which the complete nucleotide sequences were found to contain 1333-1355 nt. The 18 DNAb molecules identified consist of three main types, each associated with a different begomovirus species: 72-99 % nucleotide identity was found within one type, but only 39-57 % identity was found between types. All the DNAb molecules reported here and elsewhere contain a 115 nt conserved region that has 93-100 % identity with a consensus sequence, and have a common ORF encoding 118 amino acids on the complementary strand (designated C1). Co-agroinoculation of the DNA-A component of Tomato yellow leaf curl China virus tobacco isolate Y10, with its associated DNAb (Y10b), shows this DNAb to be involved in symptom induction in tobacco and tomato. The in-frame ATG mutation of C1 of Y10b caused much milder symptoms as compared with wild Y10b, indicating a functional role for this ORF. Pairwise nucleotide sequence identity comparisons of DNAb molecules and their cognate viral DNA-A molecules indicate that DNAb molecules have co-evolved with their cognate helper viruses. Recombination between DNAb molecules is documented and a DNAb species concept is proposed and discussed.

Tomato SlSnRK1 Protein Interacts with and Phosphorylates βC1, a Pathogenesis Protein Encoded by a Geminivirus β-Satellite

“…TYLCCNV is a monopartite begomovirus associated with a b-satellite (TYLCCNB) identified in China (Zhou et al, 2003). We demonstrated previously that TYLCCNV alone produces asymptomatic infections in tobacco, tomato, and petunia (Petunia hybrida) and that TYLCCNB is required for the production of leaf curl symptoms in these hosts (Cui et al, 2004).…”

“…The fidelity of the mutants was confirmed by sequencing. The strategy described previously (Zhou et al, 2003) was then used for the construction of infectious clones (Supplemental Table S1) of bC1 mutants.…”

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

“…Phylogenetic analysis of DNA b molecules and their cognate begomoviruses suggests that DNA b molecules have co-evolved with their helper viruses (Zhou et al, 2003b). We have demonstrated previously that DNA A of TYLCCNV alone could infect Nicotiana benthamiana, Nicotiana glutinosa, Nicotiana tabacum and tomato plants systemically but produced no symptoms, and that TYLCCNV DNA b was required, in addition, for induction of leaf curl disease in these hosts (Cui et al, 2004).…”

“…Recombinant plasmids were digested with EcoRI and inserted into the binary vector pBinPLUS, to produce plasmids pBinPLUSRecDNA-Ab-9 and pBinPLUS-RecDNA-Ab-10, containing dimeric RecDNA-Ab molecules. Plasmids pBinPLUSRecDNA-Ab-9 and pBinPLUS-RecDNA-Ab-10 were mobilized into Agrobacterium tumefaciens strain EHA105 by triparental mating as described previously (Zhou et al 2003b). Then the two clones were tested for infectivity in N. benthamiana by co-agroinoculation with the infectious clone of TYLCCNV DNA A, pBinPLUS-1.7A (Zhou et al, 2003b).…”

“…Plasmids pBinPLUSRecDNA-Ab-9 and pBinPLUS-RecDNA-Ab-10 were mobilized into Agrobacterium tumefaciens strain EHA105 by triparental mating as described previously (Zhou et al 2003b). Then the two clones were tested for infectivity in N. benthamiana by co-agroinoculation with the infectious clone of TYLCCNV DNA A, pBinPLUS-1.7A (Zhou et al, 2003b). Both pBinPLUS-RecDNA-Ab-9 and pBinPLUSRecDNA-Ab-10 were found to be infectious in N. benthamiana and produced downward leaf curling, stunting, vein darkening, vein yellowing, curly shoots and enation symptoms following co-inoculation with TYLCCNV DNA A.…”