Nucleotide sequence comparison of the 3' terminal region of the genome of pepper vein mottle virus isolates from Tunisia and Ivory Coast.

Three Tunisian PVMV isolates identified in pepper and tomato fields and one isolate from Ivory Coast were submitted to biological and molecular analysis. Phenotypically, Tunisian isolates induced mild symptoms while the Ivory Coast one is more aggressive on tobacco. As no PVMV sequence data are available, detailed sequence comparisons of coat protein gene (CP) were made. No nucleotide or amino acid changes in this region could be related to the pathogenicity of the isolates analysed. With the aim to increase our molecular understanding of the biological properties, we have sequenced the 3'-non translated region (3'NTR). Results suggest that this region of the RNA genome may be involved in the modulation of disease symptoms.

Plant lipoxygenase 2 is a translation initiation factor-4E-binding protein.

The eukaryotic initiation factor 4E (eIF4E) emerged recently as a target for different types of regulation affecting translation. In animal and yeast cells, eIF4E-binding proteins modulate the availability of eIF4E. A search for plant eIF4E-binding proteins from Arcabictopsis thaliana using the yeast genetic interaction system identified a clone encoding a lipoxygenase type 2 (AtLOX2). In vitro and in vivo biochemical assays confirm an interaction between AtLOX2 and plant eIF4E(iso) factor. A two-hybrid assay revealed that AtLOX2 is also able to interact with both wheat initiation factors 4E and 4E(iso). Deletion analysis maps the region of AtLOX2 involved in interaction with AteIF(iso)4E between amino acids 175 and 232. A sequence related to the conserved motif present in several eIF4E-binding proteins was found in this region. Furthermore, the wheat p86 subunit, a component of the plant translation eIF(iso)4F complex, was found to interfere with the AteIF(iso)4E-AtLOX2 interaction suggesting that p86 and AtLOX2 compete for the same site on eIF(iso)4E. These results may reflect a link between eIF4Es factors mediating translational control with LOX2 activity, which is probably conserved throughout the plant kingdom.

Synthesis of (-)-strand RNA from the 3' untranslated region of plant viral genomes expressed in transgenic plants upon infection with related viruses.

When expressed in transgenic tobacco plants, transgene mRNA that includes the 3' untranslated region (3' UTR) of Lettuce mosaic virus served as template for synthesis of complementary (-)-strand RNA following an infection by Tobacco etch virus, Tobacco vein mottle virus or Pepper mottle virus, but not when infected with Cucumber mosaic virus. Deletion of the 3' UTR from the transgene abolished the synthesis of (-)-strand transcripts. Similar results were obtained in transgenic tobacco plants expressing mRNA that includes the RNA3 3' UTR of Cucumber mosaic virus when infected with Tomato aspermy virus. These results show that the viral RNA-dependent RNA polymerase of several potyviruses and Tomato aspermy virus have the ability to recognize heterologous 3' UTRs when included in transgene mRNAs, and to use them as transcription promoters.

Restriction maps and homologies of the three plasmids of Agrobacterium rhizogenes strain A4.

Agrobacterium rhizogenes strain A4 is a virulent agropine-type strain possessing three plasmids: plasmid a (pArA4a, 180 kb) is not necessary for plant transformation, plasmid b (250 kb) is the root-inducing plasmid (pRiA4), and plasmid c (pArA4c) is a cointegrate of pArA4a and pRiA4. The total plasmid DNA (pArA4) of strain A4 was cloned in the cosmid pHSG262 and the library obtained was used to establish BamHI maps of the three plasmids. The plasmids a and Ri have an apparently identical region and a partly homologous region, and are different in the remaining regions including their origins of replication. Another agropine-type A. rhizogenes strain, HRI, bears only one plasmid, which is the Ri plasmid (pRiHRI). pRiHRI and pRiA4 present the same restriction maps for a great part, but are different in a region of 48 kb; however, this region of pRiHRI is found unmodified in pArA4a and may have a role in the virulence of the bacteria. The comparison between the restriction maps of the plasmids of strain A4 leads us to propose that the recombination event leading to pArA4c formation occurs within the identical regions of pArA4a and pRiA4. In addition, the comparison with the already established map of pRiHRI suggests that strain HRI could have been derived from a recombination event between the two homologous regions of pArA4c with subsequent loss of the smaller plasmid.