Geminivirus-related extrachromosomal DNAs of the X-clade phytoplasmas share high sequence similarity

Abstract

fur Land-und Forstwi rtschaft, I nstit ut fur Pf I a n ze nsc h u t z i m Obstba u, Dossenheim, Germany Pathology, University of Georgia, Griffin, Georgia Southern blot hybridization analysis revealed that the extrachromosomal DNAs (EC-DNAs) associated with Vaccinium witches' broom (VAC) and walnut witches' broom phytoplasmas and various strains of the Italian clover phyllody phytoplasma (ICPh) were highly homologous among themselves but distinct from EC-DNAs of aster yellows related phytoplasmas occurring in the same insect and plant hosts and collected a t the same site as the lCPh strains. The EC-DNAs of various strains of the lCPh differed significantly in number and size, more markedly among samples from different host plant species than among samples from the same host plant species. However, experiments on insect-mediated transmission suggested that the size variation is not associated with plant host specificity. Sequence analysis of cloned fragments revealed the presence of highly conserved ORFs (with substantially invariant putative translation products) but also the presence of regions rich in short direct and inverted repeats, which may be the cause of the size variations. The partial sequence of an EC-DNA associated with VAC encoding a putative replication-associated protein indicated their close phylogenetic relationship with geminiviruses.

In planta expression of a protein encoded by the extrachromosomal DNA of a phytoplasma and related to geminivirus replication proteins The GenBank accession number for EcOYW1 is AB010426.

“…An extrachromosomal DNA found in SCWL phytoplasma (Nakashima & Hayashi, 1997) and a plasmid, pOYW1, found in OY phytoplasma (Kuboyama et al, 1998) were also reported to be extremely AT-rich. Rekab et al (1999) reported geminivirus-related extrachromosomal DNA from an X-clade phytoplasma. Although they only reported a partial sequence, their ORFB was highly homologous to the C-terminal region of geminivirus replication proteins.…”

“…An overall similarity between a protein encoded by ORF1 and a Rep protein of Tomato golden mosaic virus (TGMV), a geminivirus, is 66 %. Homologous deduced proteins were also reported for the extrachromosomal DNA from SCWL and VAC phytoplasmas (Rekab et al, 1999 ;Nakashima & Hayashi, 1997). Some of these proteins are aligned in Fig.…”

“…1n5 kbp) and sugarcane white leaf (SCWL) phytoplasma (approx. 2n7 kbp) have been reported (Rekab et al, 1999 ;Kuske & Kirkpatrick, 1990 ;Nakashima & Hayashi, 1997). Previously, we reported a 3n6 kbp DNA fragment of the dsDNA, pOYW1, from OY-W phytoplasma and suggested that pOYW1 is a plasmid replicating by a rolling-circle replication mechanism (Kuboyama et al, 1998).…”

“…Similar to the VAC phytoplasma extrachromosomal DNA (Rekab et al, 1999), EcOYW1 contains some putative prokaryotic (k35 signal) and eukaryotic (TATA box) promoter-like signals upstream from ORF1. Furthermore, two previously unreported, long repeated sequences are found in EcOYW1 (indicated with small arrows in Fig.…”

Risks from GMOs due to Horizontal Gene Transfer

“…In particular, environments that allow frequent, multiple interactions between donor and recipient organisms favor high levels of HGT. Some examples include aquatic environments (Audic et al, 2007;Jiang and Paul, 1998), biofilms (Hendrickx et al, 2003;Sørensen et al, 2005), the human gut (Kurokawa et al, 2007;Xu et al, 2007) and cells co-infected by viruses or bacteria (Abbot et al, 2007;Rekab et al, 1999;Worobey and Holmes, 1999).…”